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Biomedical subjects

K Ryder

Publications and source records attributed to K Ryder.

45 records · Page 3Linked to original sources
PubMed1986

Intracoronary administration of streptokinase in a canine model. Disturbance in thromboxane A2-prostacyclin balance.

The potential impact of local intracoronary infusion of streptokinase (SK) on vascular prostaglandin synthetic pathways was studied in a canine model. Control animals (n = 10) underwent left coronary artery (LCA) infusion of 50,000 units SK for 90 minutes; experimental animals (n = 10) underwent LCA infusion of normal saline. Plasma samples for radioimmunoassay (RIA) of prostacyclin (PGI-2) and thromboxane (TXA-2) were obtained from the coronary sinus (CS) as follows: one sample preinfusion, six samples during infusion, and three samples postinfusion in each animal. Comparisons between control and experimental plasma levels of PGI-2 and TXA-2 were made for each sampling time. The PGI-2 levels remained at or below the lower limits of detectability by RIA (the most sensitive assay available) in both control and experimental animals. TXA-2 levels were higher in experimental than in control animals at all sampling times, with the most significant differences occurring in samples 3 (after 30 minutes of infusion, .001 less than P less than .01), 4 (after 45 minutes of infusion, .05 less than P less than .10), and 5 (after 60 minutes of infusion, .02 less than P less than .05). We suggest (1) it is unlikely that any of the beneficial effects of coronary streptokinase infusions are PGI-2-mediated, (2) that the TXA-2 increases in our model may represent a pathophysiologic-biochemical correlate of previously identified morphologic evidence of endothelial damage in animals infused with fibrinolytic agents, and (3) that our findings may indicate that fibrinolytic infusions produce competing effects: lysis of thrombi and endothelial injury with TXA-2 production.(ABSTRACT TRUNCATED AT 250 WORDS)

6-Ketoprostaglandin F1 alpha↗
PubMed1986

Measurement of total bilirubin by use of bilirubin oxidase.

We used an enzymatic method for measuring total bilirubin in serum. Results by this method varied linearly with bilirubin concentrations to at least 300 mg/L. The day-to-day precision (CV) of the method ranged from less than 1% to about 11% at bilirubin concentrations of 183 and 12 mg/L, respectively. Commonly used anticoagulants, serum preparation materials, and selected drugs had no effect on the apparent bilirubin concentration, but turbidity caused a slight increase and hemoglobin concentrations of 2 g/L resulted in lower values, by as much as 17 mg/L at a bilirubin concentration of 95 mg/L. Patients' results obtained with this enzymatic method were slightly lower than those obtained with methods based on the Jendrassik-Grof principle. The largest differences, seen in samples with high "direct" bilirubin concentrations, can be decreased by measuring the absorbance at 425 nm instead of at 465 nm as recommended by the supplier of the bilirubin oxidase method.

Adult↗
PubMed1985

Seventeen base pairs of region I encode a novel tripartite binding signal for SV40 T antigen.

Three sequence components direct high affinity binding of dimeric SV40 T antigen to SV40 origin region I. Two signals are encoded by two directly repeated 5'-GAGGC-3' pentanucleotides. Approximately equal contributions to binding stability are made by each pentanucleotide, and both spacing and orientation of the pentanucleotides are important for binding affinity. The third vital component is contained in a 5'-TTTTTTG-3' spacer sequence that separates the pentanucleotides. Sequence-specific features of the spacer stabilize binding to the adjacent pentanucleotides. The asymmetry of the spacer suggests that a novel binding mechanism is involved. Because the alignment of T antigen on mutant and wild-type DNAs is similar, we propose that any two of the three sequence signals are sufficient to determine the unique arrangement of a bound protein dimer.

Antigens, Polyomavirus Transforming↗
PubMed1984

A comparison of the bioactivity of human and bovine thyrotrophin preparations, as determined by intracellular cyclic AMP responses of cultured FRTL-5 cells and human thyroid cell monolayers.

A clonal strain of thyrotrophin (TSH)-dependent rat thyroid cells (FRTL-5) has been used to evaluate the biological activity of reference preparations of both human and bovine TSH. Using the accumulation of intracellular cyclic AMP as a response parameter, the widely used bovine TSH preparation. Armour 'Thytropar', was calibrated against the First International Standard of Thyrotrophin (pituitary TSH), bovine, for immunoassay. Log dose - log response curves were parallel, and a relative potency of 2.4 IU/unit of 'Thytropar' was obtained. Subcultures of FRTL-5 cells were more responsive to both bovine and human TSH than were human thyroid follicular cells maintained as primary monolayer cultures. Dose-response curves for cyclic AMP accumulation were parallel for a single cell type differentially incubated with human TSH (the First International Reference Preparation) and bovine TSH (Armour 'Thytropar') preparations. The relative potencies (units: IU) of bovine-human TSH were of the order of 2.0 when tested on both FRTL-5 cultures and primary human thyroid monolayers. This suggests that in the spectrum of structural differences between TSH receptors of different species, the discriminatory powers of the human and FRTL-5 cell TSH receptor are similar. Thus FRTL-5 cells form the basis of a bioassay system of considerable value in the study of human thyroid stimulators, as we demonstrate in an evaluation of two recent preparations of human TSH.

Animals↗
PubMed1983

Binding of SV40 a protein to the BK virus origin of DNA replication.

The SV40 A protein (T antigen) binds to the putative origin of replication of the related BK virus (BKV). Protection studies with dimethyl sulfate identify multiple pentanucleotide contact sites in three distinct binding regions. In addition to the consensus family of recognition sequences, 5'-(G greater than T)(A greater than G)GGC-3', previously identified in the origin of SV40, BKV contains a contact 5'-AAGGC-3' site. As in the case of SV40, each binding region contains recognition sequences in different arrangements. The high affinity region I contains two sites arranged as direct repetitions covering a span of 17 base pairs (bp). In the intermediate affinity region II, four pentanucleotides are oriented as inverted repetitions with a span of 23 bp. Low affinity region III has a single contact site that can direct binding of the A protein. These different arrangements of DNA contact sites determine different patterns of protein binding and DNase protection in the three regions. The findings support a model of A protein binding to DNA previously proposed for the SV40 origin and establish a basis for future studies on regulatory phenomena at the BKV origin.

Antigens, Polyomavirus Transforming↗
PubMed1983

Topography of simian virus 40 A protein-DNA complexes: arrangement of protein bound to the origin of replication.

DNA binding regions I, II, and III at the origin of replication have different arrangements of A protein (T antigen) recognition pentanucleotides. The A protein also protects each region from DNase in distinctly different patterns. Footprint and fragment assays led to the following conclusions: (i) in some cases a single recognition pentanucleotide is sufficient to direct the binding and accurate alignment of A protein on DNA; (ii) the A protein binds within isolated region I or II in a sequential process leading to multiple overlapping areas of DNase protection within each region; and (iii) the 23-base pair span of recognition sequences in region II allows binding and protection of a longer length of DNA than the 23-base pair span in region I. We propose a model of protein binding that addresses the problem of variations in the arrangement of pentanucleotides in regions I and II and explains the observed DNase protection patterns. The central feature of the model requires each protomer of A protein to bind to a pentanucleotide in a unique direction. The resulting orientation of protein would protect more DNA at the 5' end of the 5'-GAGGC-3' recognition sequence than at the 3' end. The arrangement of multiple protomers at the origin of simian virus 40 replication is discussed.

Antigens, Viral↗
PubMed1976

Inflammatory reaction and airway damage in cystic fibrosis.

In cystic fibrosis there is chronic infection and inflammatory reaction in the airways, accompanied by destruction and shedding of airway epithelium. Leukocytes migrate into the airways and some disintegrate, liberating deoxyribonucleoprotein that is incorporated into the gel structure of the bronchial mucus. We compared the status of these processes in cystic fibrosis with that in chronic bronchitis and bronchiectasis, by examining the sputum raised from the lower airways. Measurements also were made on sputum induced in normal subjects. The results indicate that migration of leukocytes into the airways and shedding of damaged airway epithelium were minimal in the normal subjects; they were significant in the patients with chronic bronchitis, higher in those with bronchiectasis, and still higher in those with cystic fibrosis. The large increases found in the total content of DNA and solids in the cystic fibrosis sputum were due to increases in the insoluble fraction containing the whole leukocytes and particulate debris that remained when the sputum mucus gel was solubilized with mercaptoethanol. Despite the large increases in the total content of DNA and solids, the contents of mucus gel components and of deoxyribonucleoprotein from disintegrated leukocytes actually present in the mucus gel structure of the cystic fibrosis sputum were not significantly higher than in the sputum from the patients with chronic bronchitis or brochiectasis.

Bronchi↗