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Biomedical subjects

J Jenkins

Publications and source records attributed to J Jenkins.

At least 145 records · Page 8Linked to original sources
PubMed1989

Evolutionary conservation of the biochemical properties of p53: specific interaction of Xenopus laevis p53 with simian virus 40 large T antigen and mammalian heat shock proteins 70.

We have investigated the biochemical properties of Xenopus laevis p53. With an in vitro binding assay, we can detect a specific association between X. laevis p53 and simian virus 40 large T antigen. Furthermore, X. laevis p53 expressed in monkey COS cells is stably associated with this viral antigen. Like mammalian p53, X. laevis p53 in complex with simian virus 40 large T antigen exhibits a 20-fold increase of its half-life. On the other hand, X. laevis p53 is unable to associate either in vivo or in vitro with adenovirus type 5 E1B 55-kilodalton protein. We show by an immunological technique that X. laevis p53 forms specific complexes with mammalian hsp72 and hsp73 heat shock proteins only at a temperature well above the optimal growth temperature for X. laevis. Our results suggest that the protein-binding properties of p53 are closely related to the functional activity of the protein.

Animals↗
PubMed1989

Perinatal mortality in Northern Ireland: where are we now?

Perinatal mortality in Northern Ireland has been declining over the last 30 years, but the factors which may account for this fall have not been clearly delineated. Crude perinatal mortality figures yield very little insight into the problem, and meaningful management statistics are urgently required if service performance is to be reasonably assessed. This paper sets out the case for birth-weight standardisation and explores the utility of a broad diagnostic taxonomy of causes of death.

Birth Weight↗
PubMed1988

Immunoblastic peripheral T-cell lymphoma confined to bone marrow in an infant presenting with aspergillosis.

A 16-month-old female infant presenting with pancytopenia and fever was found to have pulmonary aspergillosis and large-cell immunoblastic non-Hodgkin's lymphoma of peripheral post-thymic origin isolated to bone marrow. Extensive noninvasive evaluations failed to demonstrate the disease in other extramedullary sites. The malignant cells were large and polymorphous; lacked terminal transferase; expressed surface CD-2, CD-3, CD-8, and HLA-DR antigens, and showed rearrangements of the T-cell-receptor beta-chain gene. To our knowledge, this type of lymphoma in an infant has not been reported before. Furthermore, aspergillosis is a rare presenting feature in patients with lymphoproliferative disease. In our case, it may reflect an underlying immune deficiency associated with the transformation and proliferation of a suppressor T cell.

Aspergillosis↗
PubMed1988

Structural analysis of the 2.8 A model of Xylose isomerase from Actinoplanes missouriensis.

The structure of Xylose isomerase (X.I.) from Actinoplanes missouriensis has been solved to 2.8 Angstroms resolution. Phases were determined from a single Eu3+ derivative and from the noncrystallographic 222 symmetry of the tetrameric molecule. An atomic model was built and subjected to restrained crystallographic refinement. The resulting model is shown to be closely similar to the recently reported X.I.'s structures from three other bacterial sources. Each monomer is found to be composed of an eight-stranded alpha/beta "T.I.M." barrel forming an N-terminal domain of 328 residues followed by a large loop of 66 residues embracing an adjacent subunit. Analysis of intersubunit packing shows that the X.I. tetramer is an assembly of two tight dimers. The beta barrel fits a simple hyperboloid model as other T.I.M. barrels do. The active site, identified as the binding site for the inhibitor xylitol, is located at the carboxyl end of the beta strands in the barrel next to a pair of binding sites for Eu3+ ions, which are assumed to be sites for the divalent ions involved in catalysis. Active sites in the tetramer are oriented towards the interface between dimers. It is suggested that subunit interfaces might stabilize the active site region and this might explain the oligomeric nature of other alpha/beta barrel enzymes.

Actinomycetales↗
PubMed1988

Metal Ion Interactions with Phosphoenolpyruvate Carboxylase from Crassula argentea and Zea mays.

Metal ion interactions with phosphoenolpyruvate carboxylase from the CAM plant Crassula argentea and the C(4) plant Zea mays were kinetically analyzed. Fe(2+) and Cd(2+) were found to be active metal cofactors along with the previously known active metals Mg(2+), Mn(2+), and Co(2+). In studies with the Crassula enzyme, Mg(2+) yielded the highest V(max) value but also generated the highest values of K(m) ((metal)) and K(m) ((pep)). For these five active metals lower K(m) ((metal)) values tended to be associated with lower K(m) ((pep)) values. PEP saturation curves showed more kinetic cooperativity than the corresponding metal saturation curves. The activating metal ions all have ionic radii in the range of 0.86 to 1.09 A. Ca(2+), Sr(2+), Ba(2+), and Ni(2+) inhibited competitively with respect to Mg(2+), whereas Be(2+), Cu(2+), Zn(2+), and Pd(2+) showed mixed-type inhibition. V(max) trends with the five active metals were similar for the C. argentea and Z. mays enzymes except that Cd(2+) was less effective with the maize enzyme. K(m) ((metal)) values were 10- to 60-fold higher in the enzyme from Z. mays.

Journal Article↗
PubMed1988

Diagnosis of atrial fibrillation using electrograms from chronic leads: evaluation of computer algorithms.

This study compares the performance of three detection algorithms for the recognition of atrial fibrillation in chronic pacing leads. Multiple serial recordings were obtained of wideband and filtered electrograms from chronic atrial and ventricular leads in dogs for a period up to 55 days following implantation. Each dog was recorded in sinus rhythm and induced atrial fibrillation. Four days were chosen for processing: The day of implantation and a day in the first, second or third, and fifth weeks. Three signal processing methods were assessed for performance in detection of atrial fibrillation: software recognition of rate with automatic threshold control, amplitude distribution, and frequency spectral analysis. A software trigger for rate determination was adjusted to thresholds of 10, 20, and 30% of maximum baseline-to-peak amplitude. At 10%, a rate boundary anywhere between 420 and 560 beats per minute (bpm) perfectly separated atrial fibrillation from sinus rhythm even though atrial electrograms were contaminated with large QRS deflections and double-sensing was present. At 20% and 30%, a rate boundary around 300 bpm could be used, but sensitivity and specificity were reduced to 90%. In amplitude distribution analysis, a percent of time within a baseline window provided perfect separation of atrial fibrillation from sinus rhythm. In all cases, the signal was within this window less than 43% of the time in atrial fibrillation, and more than 43% in sinus rhythm. In spectral analysis, frequency bands were examined for power content. In the 6 to 30 Hz band atrial fibrillation contained the greater power. Choosing 58% of total power as a discriminant, sensitivity and specificity of atrial fibrillation detection were 100% and 95% respectively.

Algorithms↗
PubMed1987

Histiocytosis X and acute monocytic leukemia. Biologic illustration of the monocyte phagocytic system.

The concept of a mononuclear phagocytic system consisting of a continuum of cells arising from the bone marrow monoblast and terminating in the mature tissue macrophage is being actively investigated. The presentation of documented acute monocytic leukemia 18 months following the confirmed diagnosis of histiocytosis X in a 39-year-old man strongly supports the concept of the mononuclear phagocytic system lineage.

Adult↗
PubMed1987

Portable system for the measurement of heart rate.

We describe a simple RR interval recording system; it does not involve an analogue recording of ECG data on magnetic tape and does not therefore suffer from the inherent problem of tape speed variability on playback, which is a frequent cause of inaccuracies in RR interval timing. The system operates in both recording and playback modes and records of up to 60 minutes duration can be obtained without operator intervention. Its accuracy with respect to RR interval is not less than 99.5%.

Biomedical Engineering↗
PubMed1987

One lung anaesthesia. Cardiovascular and respiratory function compared during conventional ventilation and high frequency jet ventilation.

Ten patients about to undergo left-sided thoracotomy for carcinoma of the lung were entered into a crossover trial to compare cardiovascular and respiratory function during high frequency jet ventilation and conventional mechanical ventilation for one lung anaesthesia. All patients were anaesthetised with a standard technique using double lumen tubes and placed in the lateral position with the left chest open. The results showed no significant differences with regard to ventilation sequence but one lung high frequency jet ventilation gave higher values than one lung conventional ventilation for shunt (p less than 0.01) and positive end expiratory pressure (p less than 0.05) and lower peak inflation pressure values (p less than 0.01). There were no significant differences in cardiac output, pulmonary capillary wedge pressure, arterial carbon dioxide or available oxygen. Surgical conditions were satisfactory during both methods of ventilation and satisfactory gas exchange occurred. It was, however, more difficult to assess adequacy of ventilation during high frequency jet ventilation and the routine use of this method of ventilation is not recommended during one lung anaesthesia.

Anesthesia, Inhalation↗
PubMed1987

Psychosocial sequelae of stoma surgery for inflammatory bowel disease in childhood.

Three matched groups of children with inflammatory bowel disease: (a) stroma group, (b) ileorectal anastomosis group and (c) no-surgery group were compared for psychosocial adjustment. No differences were found between the groups for psychological adjustment, selfesteem, or quality of life. It is concluded that providing children are well prepared and followed up carefully and sensitively, then stroma surgery should not be deferred for fear of adverse psychological consequences.

Adolescent↗
PubMed1987

Hydrogel contact lenses impede carbon dioxide efflux from the human cornea.

A carbon dioxide-sensitive probe applied directly to the anterior corneal surface was used to investigate whether hydrogel contact lenses act as a barrier to carbon dioxide efflux from the human cornea. The effect of increasing periods of eye closure on carbon dioxide accumulation at the anterior corneal surface was also examined. A calibration curve to convert the CO2 probe output to equivalent carbon dioxide partial pressure (pCO2) was determined by measuring the slope of the probe output obtained after 10 minutes exposure of the corneas of three human subjects to gas mixtures containing CO2 at different nominal partial pressures. The equivalent pCO2 at the anterior corneal surface was subsequently determined for two human subjects following 10 minutes wear of hydrogel contact lenses (HEMA; 38% water content) of various center thicknesses. All lens thicknesses used (0.035 to 0.3mm) produced a significant accumulation of CO2 under the contact lens. A maximum pCO2 of approximately 50mmHg was reached with lenses of 0.15mm or greater center thickness. With short periods of eye closure, CO2 accumulated rapidly at the anterior corneal surface, reaching a steady level of approximately 45mmHg after 10 minutes of eye closure. Our results suggest that hydrogel contact lenses provide a significant barrier to carbon dioxide efflux from the cornea, the effect increasing with lens thickness. We suggest that the consequent chronic decrease in stromal pH, particularly during extended wear, may contribute to both short and long-term contact lens-induced changes in corneal endothelial cell morphology.

Adult↗