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Biomedical subjects

M D Ball

Publications and source records attributed to M D Ball.

At least 19 recordsLinked to original sources
PubMed2004

Cell interactions with laser-modified polymer surfaces.

The performance of a polymeric biomaterial depends on the bulk and surface properties. Often, however, the suitability of the surface properties is compromised in favour of the bulk properties. Altering the surface properties of these materials will have a profound effect on how cells and proteins interact with them. Here, we have used an excimer laser to modify the surface wettability of nylon 12. The surface treatment is rapid, cost-effective and can cause reproducible changes in the surface structure of the polymers. Polymers were treated with short wavelength ( < 200 nm) UV light. These wavelengths have sufficient photon energy (6.4eV) to cause bond scission at the material surface. This results in a surface reorganisation with incorporation of oxygen. Surface wettability changes were confirmed using contact angle measurements. Cell interactions with the surfaces were examined using 3T3 fibroblast and HUVEC cells. Cells morphology was examined using a confocal laser scanning microscope (CLSM). Cell activity and cell number on the treated nylon were assessed using biochemical assays for up to seven days. Both fibroblasts and endothelial cells initially proliferated better on treated compared with untreated samples. However, over seven days activity decreased for both cell types on the control samples and endothelial cell activity and cell number also decreased on the treated polymer.

3T3 Cells↗
PubMed2003

Properties of calcium phosphate coatings deposited and modified with lasers.

Physical, chemical and biological properties of calcium phosphate coatings fabricated by a pulse laser deposition method at room temperature (RT PLD) have been studied. In vitro evaluation of RT PLD coatings on bioresorbable polymers (Poly-epsilon-caprolactone and Poly-L-lactide) have been carried out. It was shown that both polymers support osteoblast growth, with increased cell activity, alkaline phosphatase activity and total protein content on those surfaces that have been coated. The advantages of RT PLD coatings in biomaterials surface optimization are discussed.

Journal Article↗
PubMed2001

Osteoblast growth on titanium foils coated with hydroxyapatite by pulsed laser ablation.

Pulsed laser ablation is a new method for deposition of thin layers of hydroxyapatite (HA) on to biomaterial surfaces. In this paper, we report activity and morphology of osteoblasts grown on HA surfaces fabricated using different laser conditions. Two sets of films were deposited from dense HA targets, at three different laser fluences: 3, 6 and 9 Jcm(-2). One set of the surfaces was annealed at 575 degrees C to increase the crystallinity of the deposited films. Primary human osteoblasts were seeded onto the material surfaces and cytoskeletal actin organisation was examined using confocal laser scanning microscopy. The annealed surfaces supported greater cell attachment and more defined cytoskeletal actin organisation. Cell activity, measured using the alamar Blue assay, was also found to be significantly higher on the annealed samples. In addition, our results show distinct trends that correlate with the laser fluence used for deposition. The cell activity increases with increasing fluence. This pattern was repeated for alkaline phosphatase production by the cells. Differences in cell spreading were apparent which were correlated with the fluence used to deposit the HA. The optimum surface for initial attachment and spreading of osteoblasts was one of the HA films deposited using 9 J cm(-2) laser fluence and subsequently annealed at 575 degrees C.

Alkaline Phosphatase↗
PubMed2001

Activities and conformational fitting of 1,4-naphthoquinone derivatives and other cyclic 1,4-diones tested in vitro against Pneumocystis carinii.

Atovaquone is a chemotherapeutic agent used to treat pneumonia caused by Pneumocystis carinii in some immunocompromised patients. A set of cyclic 1,4-diones were tested in vitro for ability to inhibit growth of P. carinii, including 22 variously substituted 1,4-naphthoquinones, one bis-1,4-naphthoquinone, and three other quinones. For comparison, the antipneumocystic primaquine and its 5-hydroxy-6-desmethyl metabolite were also tested. At 1.0 microg/ml, seven compounds inhibited growth by at least 39%, with atovaquone at 92%; of these seven, five are 2-hydroxy-1,4-naphthoquinones, while one is a 2-chloro- and another is a 2-methyl-1,4-naphthoquinone. At 0.1 microg/ml, however, the most active compound tested was the primaquine metabolite, which inhibited growth by more than 42% at this concentration. To ascertain a structure-activity relationship, all 1,4-naphthoquinones were compared conformationally by means of computer-based molecular modeling (Spartan) incorporating the Sybyl force field. Without exception, for all 21 monomers tested, the substituent at position 3 of the 1,4-naphthoquinone favored activity most strongly when it simultaneously occupied (i) space centered at about 3 A from position 3, without projecting steric bulk from the area encompassed by atovaquone's cyclohexyl ring, and (ii) roughly planar space at about 7.3 A from position 3, without projecting steric bulk perpendicularly. This structure-activity relationship may prove useful in the rational design of better antipneumocystis agents.

Antifungal Agents↗
PubMed2000

Physical, chemical, and biological characterization of pulsed laser deposited and plasma sputtered hydroxyapatite thin films on titanium alloy.

The physical, chemical, and biological properties of pulsed laser deposited (PLD) and plasma sputtered (PS) hydroxyapatite (HA) coatings were compared. Human osteoblast-like cell responses to these coatings in vitro were assayed for proliferation and phenotypic expression. PS coatings formed smooth and continuous thin films that followed the contours of the substrate surface. PLD coatings consisted of numerous spheroidal micro- and macroparticles. The crystallinity of all coatings was quantified by comparison with the HA target used for both the PS and PLD processes. The XRD and FTIR results indicated that unannealed PLD coatings deposited at room temperature had X-ray spectra consistent with an amorphous structure and were found to dissolve after only a few hours in saline solution. Annealing at 400 degrees C increased the crystallinity (87-98%), which resulted in improved stability and cell activity. The PS coatings showed greater chemical stability than the unannealed PLD coatings and contained an approximate 15% crystalline phase, increasing to 65% postannealing. Cell proliferation and alkaline phosphatase production were significantly higher on unannealed PS specimens than the other coating treatments. There may be benefits in engineering the presence of a minor percentage of a microcrystalline phase in an amorphous or nanometer scale polycrystalline HA structure.

Alloys↗
PubMed1996

The detection of lice (Bovicola ovis) in mobs of sheep: a comparison of fleece parting, the lamp test and the table locks test.

Knowledge of the presence or absence of lice in a flock of sheep enables wool growers to make informed decisions as to the need for insecticidal treatments. However, with inapparent infestations, traditional methods of detection are not sufficiently sensitive and, as a consequence, flocks may be left untreated. Conversely, the routine application of insecticide to sheep with no sign of infestation is an unnecessary cost. The sensitivity of 3 procedures for detecting lice was evaluated in 68 mobs of sheep from 50 farms. In 24 mobs of sheep known to be lightly infested, lice were detected in 17% (71%) [corrected] by either parting the fleece of 10 sheep or by the lamp test in which 8g samples of shorn wool from 30 randomly selected fleeces were placed under lamps for 10 min to repel the lice. Twenty of 23 mobs (87%) were found to be infested by the table locks test in which a 30 g sample of locks wool was dissolved in 10% sodium hydroxide and the filtered residue examined with x 40 magnification. A screening test, in which either fleeces on 5 sheep were examined by fleece parting or lice were repelled from 30 shorn fleeces for 5 minutes, detected about 60% of lightly infested mobs. When this was followed by the table locks test 91% of lightly infested mobs were detected. Conducting any one of the tests on more than one mob, and in large mobs testing more frequently, increases the sensitivity of detection of lice within the whole flock.

Animals↗
PubMed1992

Chloroplast Biogenesis 65 : Enzymic Conversion of Protoporphyrin IX to Mg-Protoporphyrin IX in a Subplastidic Membrane Fraction of Cucumber Etiochloroplasts.

The preparation from Percoll-purified cucumber (Cucumis sativus)etiochloroplasts of a subplastidic membrane fraction that is capable of high rates of Mg insertion into protoporphyrin IX is described. The plastid stroma was inactive when used either alone or in combination with the membrane fraction. Successful preparation of the subplastidic membrane fraction required that Mg-protoporphyrin chelatase was first stabilized by its substrate. This was achieved by lysing Percoll-purified plastids in a fortified hypotonic medium containing protoporphyrin IX prior to ultracentrifugation and separation of the stroma from the plastid membranes. Protoporphyrin IX became membrane bound. Other additives needed for enzyme activity fell into two groups: (a) those needed for enzyme stabilization during membrane preparation and (b) those involved in the primary mechanism of Mg insertion into protoporphyrin IX. Ethylenediaminetetraacetate belonged to the first group, magnesium belonged to the second group, and ATP belonged to both groups.

Journal Article↗
PubMed1992

Fatty-acyl esters of retinol (vitamin A) in the liver of the harp seal (Phoca groenlandica), hooded seal (Cystophora cristata), and California sea lion (Zalophus californianus).

The fatty-acid composition of retinyl esters in the livers of two species of phocid seal, the harp seal (Phoca groenlandica, n = 20) and the hooded seal (Cystophora cristata, n = 15), and one species of otariid seal, the California sea lion (Zalophus californianus, n = 6), was determined. Vitamin A ranged in concentration from 4 to 1024 nmol retinol/g liver for the phocids and from 381 to 979 nmol/g liver for the otariids. In most of the livers, retinyl palmitate was not the principal ester, and the palmitate + stearate + oleate trio of retinyl esters represented less than 50% of the total. In all samples, the retinyl esters contained 20:1, 20:4, 20:5, and 22:6 in unusually large amounts. Retinyl esters tended to be richer than whole-liver lipids in 20:5 + 22:6, whereas whole-liver lipids were richer in 18:0 and 18:2. Therefore, the pool of acyl donors used for the esterification of retinol may be distinct from that used for other lipids. Birth-to-weaning changes were seen only in the harp seals. In the pups, the hepatic vitamin-A concentration increased 454%, while the proportion of 18:0 and 20:1 in the retinyl esters rose and that of 14:0 + 16:1 and 20:4 fell. Concomitantly, in their mothers, the proportion of 20:4 increased but that of 16:0 and 18:0 decreased.

Animals↗
PubMed1991

Intraplastidic Localization of the Enzymes That Convert delta-Aminolevulinic Acid to Protoporphyrin IX in Etiolated Cucumber Cotyledons.

The intraplastidic localization of the enzymes that catalyze the conversion of delta-aminolevulinic acid (ALA) to protoporphyrin IX (Proto) is a controversial issue. While some researchers assign a stromal location for these enzymes, others favor a membranebound one. Etiochloroplasts were isolated from etiolated cucumber cotyledons (Cucumis sativus, L.) by differential centrifugation and were purified further by Percoll density gradient centrifugation. Purified plastids were highly intact, and contamination by other subcellular organelles was reduced five- to ninefold in comparison to crude plastid preparations. Most of the ALA to Proto conversion activity was found in the plastids. On a unit protein basis, the ALA to Proto conversion activity of isolated mitochondria was about 2% that of the purified plastids, and could be accounted for by contamination of the mitochondrial preparation by plastids. Lysis of the purified plastids by osmotic shock followed by high speed centrifugation, yielded two subplastidic fractions: a soluble clear stromal fraction and a pelleted yellowish one. The stromal fraction contained about 11% of the plastidic ALA to Proto conversion activity while the membrane fraction contained the remaining 89%. The stromal ALA to Proto conversion activity was in the range of stroma contamination by subplastidic membrane material. Complete solubilization of the ALA to Proto activity was achieved by high speed shearing and cavitation, in the absence of detergents. Solubilization of the ALA to Proto conversion activity was accompanied by release of about 30% of the membrane-bound protochlorophyllide. It is proposed that the enzymes that convert ALA to Proto are loosely associated with the plastid membranes and may be solubilized without the use of detergents. It is not clear at this stage whether the enzymes are associated with the outer or inner plastid membranes and whether they form a multienzyme complex or not.

Journal Article↗
PubMed1990

[Neurologic manifestations in Behçet's disease].

Neurological symptoms of Behçet's Disease are numerous and varied, connected with both the peripheral and central nervous systems. Analysis of 5 observations from Fann U. H. C. Neurological Clinic leads to the authors's conclusions on the various clinical aspects and the new etiopathogenic and therapeutic data on this ailment.

Adult↗
PubMed1988

13-cis-retinoic acid stimulates in vitro mannose 6-phosphate hydrolysis and inhibits retinol esterification and benzo[a]pyrene hydroxylation by rat-liver microsomes.

13-cis-Retinoic acid, a drug used at high doses in the treatment of recalcitrant acne, increased the permeability of rat-liver microsomal membranes to mannose 6-phosphate in vitro, as indicated by an increase in mannose-6-phosphatase activity. At the same concentrations, four other amphiphiles, including all-trans-retinoic acid, were much less effective. 13-cis-Retinoic acid also inhibited retinol esterification and benzo[a]pyrene hydroxylation in microsome preparations in vitro. Although the molecular mechanism and the reversibility of these effects have not yet been studied, the interaction of 13-cis-retinoic acid with cell membranes may well be involved in both its therapeutic and toxic manifestations.

Animals↗
PubMed1986

Acyl coenzyme A:retinol acyltransferase activity and the vitamin A content of polar bear (Ursus maritimus) liver.

Acyl coenzyme A:retinol acyltransferase activity was identified in the microsomes from a polar bear liver. The highest rate of in vitro retinol esterification was 821 pmol/min/mg microsomal protein. The in vitro esterification rate displayed a small dependence upon the concentration of exogenous protein (bovine serum albumin) and even less on the concentration of sulfhydryl-reducing agent (dithiothreitol). Vitamin A was present in the liver at a concentration of 8050 micrograms/g tissue, with 98% of the vitamin in its ester form. Retinyl palmitate was 37.3% of the total liver retinyl esters, while retinyl oleate represented 20.9%, stearate 12.8%, and linoleate 7.7%.

Acyltransferases↗
PubMed1985

Enhancement of acyl coenzyme A:retinol acyltransferase in rat liver and mammary tumor tissue by retinyl acetate and its competitive inhibition by N-(4-hydroxyphenyl) retinamide.

Retinol esterification by microsomal acyl coenzyme A:retinol acyltransferase was quantified in rat mammary tumor and liver tissue. Acyltransferase activity in the livers of mammary tumor-bearing rats was 40% of that in normal animals. In response to daily oral doses of 2 mg retinyl acetate for 18-19 days, activity increased 2.8-fold in transplanted rat mammary tumors, 4.1-fold in the livers of tumor-bearing rats, and 1.5-fold in the livers of normal rats. The in vitro esterification of retinol was competitively inhibited by all-trans-N-(4-hydroxyphenyl) retinamide (Ki = 154 microM).

Acyltransferases↗