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Biomedical subjects

B E Tucker

Publications and source records attributed to B E Tucker.

8 recordsLinked to original sources
PubMed1999

Antineoplastic agents. Part 409: Isolation and structure of montanastatin from a terrestrial actinomycete.

A Montana soil actinomycete, Streptomyces anulatus, produced (1 x 10(-2)% yield) a new cancer cell growth inhibitory cyclooctadepsipeptide named montanastatin (1) accompanied by the potent anticancer antibiotic valinomycin (2) in very high (5.1%) yields. Valinomycin but not montanastatin inhibited growth of a number of pathogenic bacteria and fungi. Interpretation of high-field (500 MHz) NMR and high-resolution FAB mass spectral data allowed assignment of the structure cyclo-(D-Val-L-Lac-L-Val-D-Hiv) to montanastatin. Valinomycin (2) was also isolated from actinomycetes cultured from a tree branch and animal feces collected in Malaysia. Streptomyces exfoliatus, isolated from the tree branch, was found to contain valinomycin in 1.6% yield, while the fecal isolate, S. anulatus, gave valinomycin in 0.9% yield.

Actinomycetales↗
PubMed1996

Pre-conditioning and dual constant composition dissolution kinetics of pulsed laser deposited hydroxyapatite thin films on silicon substrates.

The kinetics of dissolution of pulsed laser deposited crystalline and amorphous thin films of hydroxyapatite on silicon substrates were measured at 37 degrees C and a pH value of 6.5 using the dual constant composition method. Solutions in which the pulsed laser deposited films were pre-conditioned (0.15 M NaCl) remained undersaturated or slightly supersaturated with respect to hydroxyapatite after equilibrium was reached, indicating only a very small coating release and the absence of re-precipitation on the surfaces. The amorphous films released more calcium and phosphate during pre-conditioning than the more crystalline films. Dual constant composition dissolution rates decreased as film crystallinity increased. The film with the lowest dissolution rate (approximately one sixth that of a crystalline film deposited using a hydroxyapatite powder target) was fabricated using a human tooth as the laser target. During pre-conditioning of plasma-sprayed coatings, more calcium and phosphate were released than for pulsed laser deposited films, and dual constant composition dissolution rates were much higher.

Calcium Phosphates↗
PubMed1995

Degradation potential of plasma-sprayed hydroxyapatite-coated titanium implants.

The purpose of this study was to develop an analytical method for evaluating the dissolution behavior of plasma-sprayed hydroxyapatite (HAP) coatings. Six commercially available and clinically used coatings applied to nonporous titanium coupons according to their respective specifications for orthopedic devices were used in this study. Dissolution behavior was monitored by first preconditioning the implant in 0.15 mol L-1 sodium chloride solution at 37 degrees C until either equilibrium or the desired change in solution hydrogen and calcium ion concentrations had been reached. In the second step, the implants were subjected to dual constant composition (DCC) dissolution under conditions of controlled undersaturation. Results indicate that the dissolution rates of the HAP coatings may differ by as much as a factor of 5 despite the fact that analytical techniques, including X-ray diffraction and FTIR, indicate no change in crystallinity or composition of the coatings before and after the solution treatment. These results indicate that HAP coatings from different sources react very differently when placed in the same local aqueous environment. However, more work will be necessary before these in vitro results can be used to predict in vivo behavior.

Alloys↗
PubMed1995

Promoting an awareness of retractions: the Louisiana State University Medical Center in Shreveport experience.

The current mission statement of the Medical Library Association states that it is "dedicated to improving health through professional excellence and leadership of its members in the ... provision of information services and educational programs ..." With this goal in mind, retractions offer medical librarians a professional challenge to become involved in the scientific process. Through results of a survey conducted among the consortium of South Central Academic Medical Libraries (SCAMeL), this paper reveals opinions on the importance of retraction awareness and who is responsible for disseminating this knowledge. The paper also reports what the Louisiana State University Medical Center at Shreveport Library and other SCAMeL member libraries are doing to promote awareness.

Academic Medical Centers↗
PubMed1993

Isolation of the nickel-chlorin chelate tunichlorin from the South Pacific ocean sea hare Dolabella auricularia.

The Papua New Guinea shell-less mollusc Dolabella auricularia has been found to contain a series of green to blue-green chlorins. One of these compounds was found to be the nickel chelate tunichlorin [1] which was isolated previously only from the Caribbean tunicate Trididemnum solidum. Discovery of tunichlorin [1] in a sea hare suggests that its occurrence in algae-consuming marine animals may be more common than earlier realized, and it may have a role in electron transfer or other metabolic processes.

Animals↗