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Biomedical subjects

K L Rice

Publications and source records attributed to K L Rice.

At least 19 recordsLinked to original sources
PubMed2006

The nuclear oncoprotein TLX1/HOX11 associates with pericentromeric satellite 2 DNA in leukemic T-cells.

TLX1/HOX11, a DNA-binding homeodomain protein, was originally identified by virtue of its aberrant expression in T-cell leukemia and subsequently found to be crucial for normal spleen development. The precise mechanism of TLX1 function remains poorly understood, although it is known that it can act as both a transcriptional activator and repressor and can downregulate the Aldh1a1 gene in embryonic mouse spleen. Using a whole-genome PCR approach, we show here that TLX1 protein directly interacts with pericentromeric human satellite 2 DNA sequences. Such DNA is known to localize to heterochromatin, which among other roles has been implicated in gene silencing. The interaction was confirmed in vitro and in vivo by gel retardation and chromatin immunoprecipitation assays involving satellite 2 DNA, which contained sequences resembling TLX1 binding sites. Using immunofluorescence microscopy, TLX1 demonstrated a punctate pattern of staining in the nuclei of leukemic T-cells (ALL-SIL). Double labelling indicated that TLX1 colocalized with the centromeric protein CENP-B, demonstrating that the TLX1 foci corresponded to clusters of centromeric DNA. The novel interaction of TLX1 with constitutive heterochromatin adds an additional level of complexity to the intracellular functions of this transcriptional regulator and may have relevance to its roles in transcriptional repression and T-cell immortalization.

Acute Disease↗
PubMed2000

Vascular nursing Internet resources: tools for cyberspace.

An older, more complex patient population, rapidly changing treatment modalities, and nontraditional venues for health care delivery have become commonplace in managing patients with vascular disorders. The delay in dissemination of information by conventional publishing and problems in accessibility create obstacles for nurses caring for this high-risk population. The Internet provides us with many valuable resources in addressing this problem. However, obtaining clinically useful information in an efficacious manner requires a working knowledge of cyberspace. This article overviews the resources available on the Internet and gives guidelines for navigating to destinations that will yield information appropriate to vascular nursing. In addition, information has also been included on networking and sharing personal practice experiences.

Education, Nursing, Continuing↗
PubMed2000

Withdrawal of chronic systemic corticosteroids in patients with COPD: a randomized trial.

The benefits of chronic systemic corticosteroids for patients with chronic obstructive pulmonary disease (COPD) are not well established. To determine whether chronic corticosteroid treatment can be safely withdrawn in "steroid-dependent""COPD patients, we performed a double-blind, placebo-controlled study of 38 patients with steroid-dependent COPD. Patients were randomly assigned to receive their usual maintenance prednisone dose for 6 mo (continuous group) or to be withdrawn from prednisone at a rate of 5 mg per week (demand group). The number of COPD exacerbations per patient (primary outcome) was 2.5 +/- 2.7 (mean +/- SD) in the continuous group and 2.7 +/- 2.5 in the demand group (p = 0.60, 95% confidence interval for the difference: -1.1 to 1.7). Spirometric results, dyspnea, and health-related quality of life did not differ significantly in the two groups. The average daily corticosteroid dose was 10.7 +/- 5.2 mg in the continuous group and 6.3 +/- 6.4 mg in the demand group (p = 0.003). Weight decreased in the demand group by 4.8 +/- 2.0 kg, compared with an increase in the continuous group of 0.5 +/- 3.5 kg (p = 0.007). Discontinuation of chronic systemic corticosteroid treatment in steroid-dependent COPD patients did not cause a significant increase in COPD exacerbations, but did reduce total systemic corticosteroid use and body weight. Larger studies may be warranted to establish the relative risks and benefits of chronic corticosteroid treatment of patients with COPD.

Aged↗
PubMed1999

Measuring thigh BP.

Explore the source record for details and available documents.

Blood Pressure Determination↗
PubMed1993

Comparison of operative reconstruction and percutaneous balloon dilatation for central venous obstruction.

To evaluate the efficacy of venous reconstruction versus percutaneous transluminal angioplasty for the treatment of obstruction of the superior vena cava and its major tributaries, we retrospectively reviewed the clinical course of 27 patients, of whom 13 underwent operative reconstruction and 15 had angioplasty (1 had both). Three patients had obstruction of the superior vena cava, 8 had occlusion of the innominate veins, and 16 had obstruction of the subclavian or axillary veins. In both treatment groups, mean age, indications, etiology, and location of the lesion were comparable. No major surgical complications occurred; one patient who underwent angioplasty experienced stent migration to the pulmonary artery without sequelae. Primary symptomatic relief at 1 year was achieved in 88% in the surgical group versus 36% in the angioplasty group (p < 0.05 by Fisher's exact test) and at 2 years in 71% versus 0%, respectively (p < 0.01). One- and 2-year success rates with repeated angioplasty, however, were 86% and 66% (p > 0.9), respectively. We conclude that the long-term success rate of operative reconstruction exceeds that of single percutaneous transluminal angioplasty. However, with repeated angioplasty, success rates approach those of operative reconstruction.

Aged↗
PubMed1992

H2O2 injury causes Ca(2+)-dependent and -independent hydrolysis of phosphatidylcholine in alveolar epithelial cells.

Oxidants may play a central role in the pathogenesis of adult respiratory distress syndrome, and phospholipase activation is a potential mechanism of oxidant-induced injury of alveolar epithelial cells. Studies were performed in rat alveolar type II epithelial cells (RAEC) after 3 days in culture. As measured by 51Cr and lactate dehydrogenase release, H2O2 caused time- and dose-dependent cytotoxicity to RAEC. RAEC phospholipids labeled with [14C]-stearic acid ([14C]SA) and [3H]arachidonic acid ([3H]AA) released free fatty acids in response to H2O2 in a manner that closely paralleled the cytotoxicity indexes. Analysis of phospholipid subclasses indicated that phosphatidylcholine was preferentially affected. Analysis for putative products of phospholipase activity revealed significant increases in diacylglycerol and phosphorylcholine, expected products of phospholipase C, as well as significant increases in L-alpha-lysophosphatidylcholine and L-alpha-glycerophosphocholine, expected products of phospholipase A2. Increases in phospholipase D activity were not detected. To determine whether H2O2-stimulated phospholipase activity might be Ca2+ stimulated, RAEC were loaded with fura-2/AM, and changes in intracellular Ca2+ concentrations ([Ca2+]i) were monitored by epifluorescent microscopy. Exposure to H2O2 caused elevations in [Ca2+]i, and the time and dose relationships were consistent with the hypothesis that the release of [14C]SA and [3H]AA is related to changes in cellular Ca2+ concentrations. Additionally, pretreatment with MAPTAM, an intracellular chelator of calcium, partially blocked H2O2-mediated [3H]AA liberation. However, experiments in saponin-permeabilized RAEC, in which [Ca2+]i was strongly buffered by ethylene glycol-bis(beta-aminoethyl ether)-N,N,N',N'-tetraacetic acid, indicate that H2O2-induced phospholipase activity also has a Ca(2+)-independent component.(ABSTRACT TRUNCATED AT 250 WORDS)

Adenosine Triphosphate↗
PubMed1992

Amiodarone-induced endothelial injury is associated with phospholipase C-mediated hydrolysis of membrane phospholipids.

Phospholipids accumulate within the lysosomes of various cells from individuals taking amiodarone. Studies on cultured cells suggest that inhibition of lysosomal phospholipase A1 and phospholipase A2 by amiodarone may be responsible for this derangement in phospholipid metabolism. Inhibition of lysosomal phospholipases by amiodarone has been suggested as a mechanism of its toxicity, but this relationship has not been clearly established. To examine this question, membrane phospholipids of cultured bovine pulmonary artery endothelial cells (BPAEC) were labeled with 14C-stearic acid, 3H-arachidonic acid, 14C-choline, or 14C-ethanolamine. Radiolabeled BPAEC were then exposed to various concentrations of amiodarone, and endothelial phospholipase activity was measured by isolating and quantifying various phospholipase products. These findings were compared to a standard indicator of endothelial cytotoxicity using 51Cr release. Six-hour exposures to 5 to 20 micrograms/ml amiodarone produced no BPAEC toxicity and were accompanied by some evidence of decreased phospholipid hydrolysis. At concentrations above 20 micrograms/ml, amiodarone caused significant BPAEC toxicity as indicated by 51Cr release, and this was closely associated with the liberation of substantial amounts of 3H-arachidonic acid and 14C-stearic acid from phosphatidylcholine and phosphatidylethanolamine. In BPAEC labeled with 14C-choline and 14C-ethanolamine, cytotoxic doses of amiodarone caused accumulations of 14C-phosphocholine and phosphorylethanolamine, expected products of phospholipase C, but without increases in phospholipase A products. We conclude that exposure of BPAEC to toxic concentrations of amiodarone is associated with extensive hydrolysis of phosphatidylcholine and lysophosphatidylethanolamine via a phospholipase C-specific mechanism, and suggest that this may be a mechanism in the pathogenesis of amiodarone toxicity.

Amiodarone↗
PubMed1991

Relationship of oxidant-mediated cytotoxicity to phospholipid metabolism in endothelial cells.

Exposure to oxidants permeabilizes cell membranes and liberates unesterified fatty acids (UFA) in a variety of cell types, including endothelial cells. Products of phospholipase activity, particularly UFA and lysophosphatides, possess potent detergent-like properties, and we postulated that oxidant injury might be mediated by the accumulation of these toxic phospholipase products. Several radiolabels were incorporated into defined positions in the phospholipids of cultured, confluent bovine pulmonary endothelial cells (BPAEC). The release of radiolabeled fatty acids and the accumulation of cell-associated phospholipase products were measured and compared to a standard cytotoxicity assay (51Cr release) in response to an oxidant stress, in this case 0.1 to 10 mM hydrogen peroxide (H2O2). H2O2 caused time- and dose-dependent 51Cr release as well as liberation of saturated ([14C]stearic acid) and unsaturated ([3H]arachidonic acid) fatty acids and the accumulation of phospholipase A2 and C products. The ability of BPAEC to incorporate UFA into complex phospholipids was shown to be severely impaired in the presence of H2O2. Further studies showed that H2O2 caused depletion of BPAEC adenosine triphosphate (ATP) content to undetectable levels, and that the depletion of cellular ATP by iodoacetic acid induced substantial release of [3H]arachidonic acid but not [14C]stearic acid from BPAEC. This finding suggests that release of UFA in response to an oxidant stress may be due in part to a defect in ATP-dependent reacylation pathways and need not reflect any increase in phospholipase activities. Also unsaturated fatty acids were found to be toxic to BPAEC upon adding them to supernatants of cultured monolayers.

Adenosine Triphosphate↗
PubMed1991

Cadmium ion-induced alterations of phospholipid metabolism in endothelial cells.

Cadmium exposure is capable of causing acute and chronic lung injuries, but the specific pathogenetic mechanisms are uncertain. The effects of cadmium ion (Cd2+) on phospholipid metabolism were examined in cultured bovine pulmonary artery endothelial cells (BPAEC), as endothelial cells appear to be particularly vulnerable to the toxic effects of this metallic ion. Exposure of radiolabeled BPAEC to millimolar concentrations of Cd2+ causes liberation of substantial amounts of [3H]arachidonic acid ([3H]AA), but only small amounts of [14C]stearic acid, from each of the major phospholipid subclasses. Analyses of hydrolytic products in BPAEC radiolabeled with [3H]myo-inositol and exposed to Cd2+ indicate that degradation of complex phospholipids is mediated by phospholipase A2. The ability of BPAEC to incorporate fatty acids or lysophosphatides into complex phospholipids is similarly impaired after exposure to Cd2+, suggesting that the liberation of [3H]AA might be due to impairment of reacylation mechanisms and not to increased hydrolytic activity of phospholipase A2. Of the two enzymes involved in reacylation reactions, Cd2+ is found to inhibit the activity of arachidonyl-specific acyl coenzyme A synthetase but not the activity of acyltransferase. Cd2+ also causes a profound time- and dose-dependent depletion of adenosine triphosphate levels in BPAEC, and these changes closely correlate with the liberation of [3H]AA. We suggest that impairment of reacylation mechanisms, and the consequent accumulation of arachidonic acid, may be important in the development of the acute inflammatory reaction that is characteristic of Cd(2+)-induced lung injury.

Adenosine Triphosphate↗
PubMed1990

Calcium ionophores injure alveolar epithelial cells: relation to phospholipase activity.

Phospholipases and certain of their hydrolytic products are toxic to alveolar epithelial cells. Since many intracellular phospholipases are Ca2+ dependent, we postulated that elevating cytosolic Ca2+ with ionophores might cause epithelial injury via phospholipase activation. Isolated perfused hamster lungs exposed to an Ca2+ ionophore A23187 develop functional evidence of severe epithelial injury. Ultrastructural studies show widespread lysis of type I epithelial cells, with only minimal abnormalities in other lung cells, including the microvascular endothelium. Analysis of whole lung lipid extracts reveals a modest elevation in free arachidonic acid but no changes in other putative products of phospholipase activity. Parallel studies were performed in cultured cells of pulmonary origin. As measured by 51Cr release, A23187 causes substantial cytotoxicity in 3-day-old cultures of rat type II alveolar epithelial cells (RAEC) but not in cultured bovine pulmonary artery endothelial cells (BPAEC). RAEC prelabeled with [14C]stearic acid [( 14C]SA) and [3H]arachidonic acid [( 3H]AA) release radiolabeled free fatty acids (FFA) in response to A23187 in a dose- and time-dependent manner that parallels the cytotoxicity index. Analyses of putative phospholipase products in cells radiolabeled with [14C]SA and [3H]AA, with [14C]choline, or with [14C]ethanolamine suggest that liberation of radiolabeled FFA may be due to several phospholipases but with principal activity being exhibited by a phospholipase C having specificity toward phosphatidylcholine and phosphatidylethanolamine. Prelabeled BPAEC release only minimal quantities of FFA in response to A23187 under the same conditions. These studies demonstrate that elevations of intracytoplasmic Ca2+ are capable of severely and selectively damaging alveolar epithelial cells and that the injury is associated with activation of intracellular phospholipases. These findings may have implications in regard to the pathogenesis of acute lung injury in humans.

Animals↗
PubMed1988

Endobronchial Richter's syndrome. A rare manifestation of chronic lymphocytic leukemia.

Endobronchial involvement in chronic lymphocytic leukemia is rare. This report describes a patient with chronic lymphocytic leukemia and Richter's syndrome in whom bronchial obstruction occurred due to massive peribronchial lymphadenopathy and endobronchial leukemic infiltrates. Endobronchial Richter's transformation has not been previously reported.

Bronchi↗
PubMed1988

Effects of phospholipase A2 and its hydrolytic products on alveolar epithelial permeability and elastase-induced emphysema.

To cause emphysema, proteases that are instilled into the air spaces must first be transported across the alveolar epithelium, a barrier that is normally quite impermeable to macromolecules. It was postulated that phospholipase A2 (PLA2) exposure would potentiate porcine pancreatic elastase (PPE)-induced epithelial solute permeability in a manner similar to that which was previously shown with lysophosphatidylcholine (lysoPC), a naturally occurring, membrane-perturbing agent that is formed principally through the hydrolysis of phosphatidylcholine by PLA2. Groups of hamsters were given intratracheal injections of PLA2 (0.3 units) or one of the expected hydrolytic products of PLA2 in equimolar concentrations, lysoPC (135 micrograms), arachidonic acid (AA) (100 micrograms), or palmitic acid (PA) (70 micrograms) with or without PPE (4 units). Epithelial permeability surface area products (PS) of the alveolar epithelium to [14C]sucrose and 125I-labeled neutral dextran (MW, 70,000) were measured in isolated perfused lungs 30 min after instillation, and emphysema severity was assessed at 3 wk by pressure-volume relationships and by mean linear intercepts. Additionally, the effects of lysoPC, PA, and AA on the functions of PPE and alpha 1-antiprotease (alpha 1 PI) in vitro were evaluated. Sucrose and dextran 70 PS differed significantly from controls only in those groups of hamsters that received PLA2 of lysoPC (p less than 0.05). LysoPC and PLA2 also potentiated the severity of PPE-induced emphysema to a similar degree (p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1988

Pulmonary infiltrates associated with noncytotoxic drugs.

A wide variety of noncytotoxic drugs, including antibiotics, analgesics, narcotics, and psychotrophic and cardiovascular agents, may cause lung injury accompanied by roentgenographic infiltrates. The clinical manifestations of drug-induced lung disease are protean. Patients may present with acute injury resembling the adult respiratory distress syndrome, which must initially be distinguished from bacterial sepsis. Other drug-associated lung injury is characterized by a more subacute pneumonitis similar to an atypical infectious pneumonia. Finally, some drugs may cause insidiously progressive pulmonary infiltrates that share features with granulomatous infections. The more common drug reactions are discussed in this review, and, although the features of drug-induced lung disease are often relatively nonspecific, those features that either mimic infectious causes or may be helpful in differentiating these processes from infections are given particular emphasis.

Diagnosis, Differential↗
PubMed1987

Effects of chronic administration of codeine and promethazine on breathlessness and exercise tolerance in patients with chronic airflow obstruction.

It has been reported that short-term treatment with relatively high doses of opiates or promethazine causes improvements in dyspnoea and exercise tolerance in patients with chronic airflow obstruction (CAO). This study was designed to determine whether initial benefits were sustained during chronic administration of codeine or promethazine and to compare the two drugs in terms of their efficacy and possible mechanisms of action. Eleven patients with stable CAO were entered into a double-blind, randomized cross-over trial in which codeine (30 mg four times daily) or promethazine (25 mg four times daily) were orally administered for 1-month periods. Treatment effects were assessed by spirometry, arterial blood gases, 12-minute walk distance and subjective dyspnoea ratings. A statistically significant increase from the baseline in mean arterial PCO2 at at 24 hours (P less than 0.01) and at 1 month (P less than 0.05) occurred with codeine administration. There was no significant change from baseline for any other measurement with either drug, and no differences were detected between the two treatment arms. Four of the eleven patients did not complete the study; three of the four experienced worsening of their CAO requiring hospitalization (two while receiving codeine, one while receiving promethazine). We conclude that chronic treatment with either codeine or promethazine provides uncertain benefits to patients with CAO which may not outweigh potential risks.

Aged↗