Biomedical subjects

D Davidson

Publications and source records attributed to D Davidson.

At least 127 records · Page 7Linked to original sources

PubMed1995

The function and evolution of Msx genes: pointers and paradoxes.

The Msx genes of vertebrates comprise a small family of chromosomally unlinked homeobox-containing genes related to the Drosophila gene muscle-segment homeobox (msh). Despite their ancient pedigree, the Msx genes are expressed in a range of vertebrate-specific tissues, including neural crest, cranial sensory placodes, bone and teeth. They are active in numerous systems, which have been used as models to study pattern formation and tissue interaction, and are, therefore, attracting a growing interest among developmental biologists. But beyond their presumed role as transcription factors, we do not know what their functions are in the cell or the embryo. Here, I review recent evidence that is beginning to address this problem and might eventually increase our understanding of how the vertebrate embryo has evolved.

Amino Acid Sequence↗

PubMed1995

The acceptability of resin therapy to patients attending a hospital lipid clinic.

Low dose cholestyramine ('Questran A') and colestipol ('Colestid Orange') were compared in a blinded two period crossover study of 55 patients attending a hospital lipid clinic. Colestipol was rated higher on a combined acceptability/palatability score. Both treatments reduced low density lipoprotein (LDL) cholesterol to a similar extent.

Adolescent↗

PubMed1995

Effects of ciprofloxacin and protamine sulfate combinations against catheter-associated Pseudomonas aeruginosa biofilms.

Infection is a common complication associated with the use of transcutaneous and implanted medical devices. These infections are generally difficult to treat and frequently require removal of the biomaterial before the infection can be completely eradicated. The presence of a bacterial biofilm recalcitrant to treatment often mediates these infections. We studied the influence of a polycationic protein, protamine sulfate, on the efficacy of the fluoroquinolone ciprofloxacin against a clinical isolate of Pseudomonas aeruginosa. A P. aeruginosa biofilm was developed on 1-cm sections of red rubber catheter material and then treated with various combinations of protamine sulfate and ciprofloxacin. The present work demonstrated that ciprofloxacin in combination with protamine was more effective against biofilms than was ciprofloxacin alone. Protamine sulfate at 50 micrograms/ml combined with antibiotic at 0.5 microgram/ml reduced the number of viable cells by an average of 98.97%, while protamine sulfate at 50 micrograms/ml alone resulted in an average 107.8% increase and antibiotic alone resulted in an average 58.6% reduction after 24 h. Furthermore, protamine sulfate, in combination with ciprofloxacin, inhibited P. aeruginosa in a dose-dependent fashion. It was further observed that treatment with the combination of protamine sulfate and ciprofloxacin had a more drastic effect on planktonic organisms as compared with the P. aeruginosa biofilms; the MBC was reduced to < 0.05 microgram/ml in the presence of 25 micrograms of protamine sulfate per ml. These findings were substantiated by ultrastructure studies of treated cells using scanning and transmission electron microscopy. The synergism between ciprofloxacin and protamine sulfate significantly enhanced the efficacy of ciprofloxacin against planktonic and biofilm P. aeruginosa.

Anti-Bacterial Agents↗

PubMed1995

Elevated urinary leukotriene E4 in chronic lung disease of extreme prematurity.

We determined if pulmonary peptidoleukotrienes contribute to the pathogenesis of chronic lung disease of extreme prematurity (CLD) by measuring urinary leukotriene E4 (uLTE4). Study patients had a birth weight < 1000 g and were about 28 d old when they were classified as normal control subjects (n = 8) or as having CLD (n = 26, abnormal chest X-ray, supplemental O2 requirement +/- ventilator). Urinary LTE4 levels were significantly elevated in CLD compared with the control group (288 +/- 92 versus 35 +/- 10 pg/mg creatinine, mean +/- SE, p < 0.05). Ventilator-dependent CLD patients, who required dexamethasone and had demonstrated uLTE4 levels above the normal range, needed significantly higher peak inspiratory pressures (20 +/- 1 cm H2O versus 15 +/- 1 cm H2O) than similar patients with uLTE4 in the normal range, and the former group had a significant reduction in uLTE4 in the first 5 d of dexamethasone therapy (626 +/- 198 to 451 +/- 176 pg/mg Cr) as ventilatory support was reduced. We conclude that peptidoleukotriene production is activated in patients with CLD (and no other detectable organ dysfunction) to pathophysiologic levels described in adults with acute asthma. Prospective studies focused on infants dependent on high levels of ventilatory support may provide insights into the role of leukotriene synthesis inhibitors or receptor antagonists in the treatment of CLD.

Bronchopulmonary Dysplasia↗

PubMed1995

Comparative differences and combined effects of interleukin-8, leukotriene B4, and platelet-activating factor on neutrophil chemotaxis of the newborn.

IL-8, leukotriene B4 (LTB4), and platelet-activating factor (PAF) are potent neutrophil chemoattractants that have been identified in inflammatory conditions of the newborn such as chronic lung disease of extreme prematurity. The aims of this study were to determine the relative potency and combined effects of these mediators on chemotaxis of polymorphonuclear leukocytes (PMN) from the newborn and to compare the effect of combining all three mediators on chemotaxis of PMN from newborns and adults. Neutrophils were isolated from cord blood (n = 17) or healthy adults (n = 4) and incubated in a 3-tier, 48-well chemotaxis chamber. For PMN from newborns, using chemoattractant concentrations ranging from 0.01 to 100 nM, we found that there were significant differences in potency: IL-8 > LTB4 > PAF. Migration to each of these mediators was almost completely due to chemotaxis as opposed to chemokinesis. At submaximal chemotaxis, using equally effective doses of IL-8 (0.2 nM), LTB4 (1.0 nM), and PAF (10 nM), the combination of all three mediators increased chemotaxis 2.4-fold above the average individual responses. Further studies indicated this increase in chemotaxis was due to the combination of IL-8 and PAF or IL-8 and LTB4; but there was no increase in chemotaxis when PAF and LTB4 were combined. The combination of all three submaximal doses of chemoattractants resulted in PMN chemotaxis that was still 36% of the adult response.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995