Search PubMed⌕ Search

Biomedical subjects

P Downey

Publications and source records attributed to P Downey.

18 recordsLinked to original sources
PubMed1997

Endothelial cell markers in chronic uremia: relationship with hemostatic defects and severity of renal failure.

Plasma von Willebrand factor antigen, soluble thrombomodulin, and tissue factor were increased in 31 patients with severe chronic renal failure (creatinine clearance <20 ml/min) under conservative treatment, whereas plasminogen activator inhibitor antigen did not differ significantly from healthy controls. No correlation among plasma levels of these proteins was found. Three patterns of relationship between endothelial cell markers and hemostatic defects were identified: 1) Plasma thrombomodulin, a marker of endothelium damage, was found an independent predictor of bleeding time and platelet aggregation, and secretion defects, and was also related to the severity of renal failure; 2) von Willebrand factor antigen, an index of endothelial cell activation and secretion, was significantly correlated with intravascular markers of thrombin and plasmin generation and with platelet adenosine triphosphate content, but not with plasma creatinine levels; and 3) tissue factor and plasminogen activator inhibitor antigen levels were not statistically correlated with the diverse hemostatic defects. Activation of coagulation and fibrinolysis, secondary to endothelial cell activation, appearing early during the evolution of chronic renal failure, is pathogenically related to the platelet dysfunction, and probably to development of atherosclerosis and thrombotic events in this disease. The progression of chronic renal failure, through endothelial cell damage, would lead to aggravation of the platelet functional defect potentiating the hemorrhagic risk.

Antigens↗
PubMed1997

Recombinant human erythropoietin as a treatment for anemia of prematurity.

Anemia of prematurity (AOP) is an exaggerated form of the normal physiologic anemia of infancy. The primary pathophysiologic abnormality implicated in the development of AOP is inadequate production of erythropoietin, whose function is the regulation of red blood cell production. Recent studies into the safety and efficacy of recombinant human erythropoietin in infants with AOP have demonstrated consistently a rise in hematocrits and reticulocyte counts, fewer blood transfusions, reduced transfused volume of blood per kilogram body weight, and a decrease in bioavailable iron. Current dose recommendations are 200 U/kg subcutaneously or intravenously daily or every other day.

Anemia, Neonatal↗
PubMed1997

Benign prostatic hyperplasia.

Benign prostatic hyperplasia is a common problem in men over 50, causing unpleasant symptoms. This Update examines the range of treatments now available, including traditional interventions and modern techniques.

Humans↗
PubMed1997

Prostate cancer.

Explore the source record for details and available documents.

Adult↗
PubMed1996

Update on the management of status asthmaticus.

Asthma is a common and debilitating problem in children. Its many costs to society include morbidity, hospitalization and treatment expenses, and a rising mortality rate. This paper examines recent trends in therapy for status asthmaticus. Oxygen, inhaled beta-adrenergic agonists, and corticosteroids remain the cornerstones of therapy for the child with a severe exacerbation of asthma. Ipratropium bromide provides additional bronchodilatation in the patient who does not respond to standard therapy. Theophylline may have a role in chronic outpatient management of asthma, but the data supporting the addition of this medication in acute therapy for status asthmaticus are inconclusive. Antibiotics are only indicated in children with asthma complicated by infection, such as sinusitis or pneumonia. Magnesium sulfate and heliox may have a role in helping the asthmatic child who is critically ill and for whom other interventions have failed. Mechanical ventilation has many complications. The concept of permissive hypercapnia may be important in limiting barotrauma. Prevention of exacerbations of asthma include limiting environmental exposure to allergens and tobacco, using corticosteroids, and reinforcing compliance with therapy.

Adrenal Cortex Hormones↗
PubMed1996

Hemostatic disorder of uremia: the platelet defect, main determinant of the prolonged bleeding time, is correlated with indices of activation of coagulation and fibrinolysis.

Several parameters of primary hemostasis and markers of activation of coagulation and fibrinolysis were measured in 48 patients with severe (creatinine clearance < 20 ml/min) chronic renal failure (CRF) without dialysis and disease or drugs affecting hemostasis. Bleeding time (BT) was prolonged in 25/48 patients, and was correlated with age of patients, severity of renal failure, hematocrit, impairment in platelet aggregation-secretion and decrease in platelet ATP content. Defects in von Willebrand factor played no role in the prolongation of the BT. Multivariate analysis showed that only platelet dysfunction and severity of renal disease were independent predictors of the BT in uremia. The platelet functional disorder was significantly correlated with a reduction in platelet ATP and ADP. High levels of plasma thrombin-antithrombin complexes (TAT), prothrombin fragment F1 + 2, fibrinogen and factor VIIc were observed in patients with CRF, as described in prethrombotic states. Plasmin-antiplasmin complexes (PAP), fibrinogen and fibrin degradation products (FgDP, FnDP) were significantly increased, and the activity of plasminogen activator inhibitor (PAI-1) was slightly reduced, denoting an activation of fibrinolysis. A negative correlation was found between platelet levels of ATP and ADP with plasma TAT, F1 + 2 and PAP. Furthermore, plasma PAI-1 activity was negatively correlated with the BT and was lower in patients with prolonged BT as compared with controls and patients with normal BT. These links between primary hemostasis and activation of coagulation and fibrinolysis suggest that increased intravascular generation of thrombin and/or plasmin is an important mediator of the defects in primary hemostasis, prolongation of the BT and, probably, bleeding in CRF.

Adolescent↗
PubMed1993

The use of a DNA probe and PCR to examine the distribution of the aac(6')-Ic gene in Serratia marcescens and other gram-negative bacteria.

A nucleotide probe for the chromosomal aminoglycoside 6' acetyltransferase gene (aac(6')-Ic) of Serratia marcescens was used in non-radioactive dot-blot hybridization experiments with 186 strains belonging to ten different species of Serratia. The gene was only detected in strains of S. marcescens (all strains tested), and positive hybridization was seen irrespective of whether or not strains were kanamycin-resistant. An additional 180 strains belonging to 28 Gram-negative bacterial species other than in the genus Serratia did not hybridize with the probe. A rapid PCR test for the aac(6')-Ic gene was developed and used to confirm that the aac(6')-Ic gene is only found in S. marcescens. Southern hybridization analysis of S. marcescens chromosomal DNA demonstrated that the gene was usually located on a PvuII fragment with a putative isoleucine tRNA-2 gene, but polymorphisms with respect to the size of this fragment were observed.

Acetyltransferases↗
PubMed1992

Characterization of the chromosomal aac(6')-Ic gene from Serratia marcescens.

The DNA sequence of the chromosomal aac(6')-Ic gene from Serratia marcescens, which had been previously cloned (H. M. Champion, P. M. Bennett, D. A. Lewis, and D. S. Reeves, J. Antimicrob. Chemother. 22:587-596, 1988) was determined. High-pressure liquid chromatographic analysis of extracts prepared from Escherichia coli carrying the chromosomal aac(6')-Ic gene on a plasmid confirmed the presence of 6'-N-acetyltransferase activity in this strain, which was suggested by the aminoglycoside resistance profile. DNA sequence analysis of the cloned 2,057-bp PstI fragment revealed several regions of homology to previously characterized sequences from GenBank, including the rpoD and tRNA-2 genes of E. coli. Subcloning experiments confirmed the coding sequence of the aac(6')-Ic gene to be at positions 1554 to 1992. The predicted amino acid sequence of the AAC(6')-Ic protein suggested that it was the third member of a family of AAC(6') proteins which included a coding region identified between the aadB and aadA genes of Tn4000 and an AAC(6') protein encoded by pUO490, which was isolated from Enterobacter cloacae. Primer extension analysis suggested that the -35 region of the aac(6')-Ic promoter overlapped a large palindromic sequence which may be involved in the regulation of the aac(6')-Ic gene. Hybridization experiments utilizing a restriction fragment from the aac(6')-Ic gene showed that all S. marcescens organisms carried this gene whether or not the AAC(6')-I resistance profile was expressed. Organisms other than Serratia spp. did not hybridize to this probe.

Base Sequence↗
PubMed1975

Control of responding by sound location in monkeys: rapid acquisition in darkness.

Rapid control of responding by sound location is obtained in squirrel monkeys when sound stimuli are presented from one of two loudspeakers, each one adjacent to a response key. With this arrangement of loudspeakers and response keys, squirrel monkeys quickly learn to respond on the key near the source of the sound stimulus, and this pattern is the same whether or not responses near the sound source are differentially reinforcedmthis result may depend on a pre-experimental tendency in squirrel monkeys to orient head and eyes toward a sound, which would lead the animal to look at the response key in front of the loudspeaker producing the sound. The present experiment sought to determine whether visual stimuli are necessary for rapid control of responding by sound location. Two monkeys were trained in darkness in a sound-localization task similar to that described above. Results were similar to those obtained from animals trained in light, indicating that visual stimuli are not required for rapid acquisition of sound-localization behavior in monkeys.

Animals↗
PubMed1972

Control of responding by location of auditory stimuli: role of differential and non-differential reinforcement.

Sound was presented to monkeys through one of two loudspeakers, each adjacent to a response key. A response on the key adjacent to the sound source was reinforced (correct response). A response on the other key produced a timeout (incorrect response). Under these conditions, over 90% of responses were correct within one or two sessions. When the procedure was changed so that a response on either key was reinforced independently of which speaker was sounding, similar control by location developed within one or two sessions. When conditions were modified by moving the keys away from the immediate vicinity of the speakers, the animals required about 20 sessions to reach a stable level of greater than 90% correct responses under differential reinforcement conditions. No control by location developed under nondifferential reinforcement conditions.

Acoustic Stimulation↗
PubMed1971

Control of responding by location of auditory stimuli: rapid acquisition in monkey and rat.

Monkeys require a considerably larger number of trials to bring responding under the control of the location of an auditory stimulus than cats, rats, and bats with the same experimental procedures. The present experiment sought to determine the conditions necessary for rapid acquisition of control of responding by location of noise and tone bursts in the monkey. Monkeys were run in an enclosure that contained four loudspeakers and four manipulanda. Two conditions were used in training. In the adjacent condition, a stimulus (noise or tone burst) was presented through one or other of two speakers and a response on the manipulandum adjacent to the speaker was reinforced with food. In the nonadjacent condition, a stimulus was presented through one of two speakers and a response on a manipulandum remote from the speaker was reinforced with food. Acquisition of control was measured by change in the percentage of reinforced responses during training. In the adjacent condition, responding came under control of location within zero to three sessions. In nonadjacent conditions, the animals required 14 to 20 sessions to come under control of location. These latter numbers are comparable to those reported in the literature for localization discrimination in monkeys.

Animals↗
PubMedDate not supplied

Perfect timing.

Explore the source record for details and available documents.

Humans↗