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Biomedical subjects

D Gilliland

Publications and source records attributed to D Gilliland.

17 recordsLinked to original sources
PubMed2007

Micro-spot, UV and wetting patterning pathways for applications of biofunctional aminosilane-titanate coatings.

The micropatterning of functional films for biomedical applications is a key part of the process leading to a precise application. In the present work we present three different methodologies to micro-design biofunctional aminosilane-titanate coatings. The chemical functionality of the surface immobilized amino groups was initially tested by surface characterization techniques. X-ray photoelectron spectroscopy was used to analyze the films before and after derivatization with Trifluoromethylbenzaldehyde while atomic force microscopy was used to study the adsorption kinetics onto these hybrid films. The three micropatterning pathways were selected for three different kinds of applications: (1) 300 microm spots were satisfactorily used for oligonucleotide immobilization, (2) Masked regions protected from UV irradiation were intensively coated by colloidal gold nanoparticles creating a drastic contrast with respect to the UV exposed areas, and (3) radial micro stripes, used afterwards for culturing cells, were created onto Si substrates by wetting from modified precursor solutions. The results are a clear indication of the versatility of hybrid aminosilane-titanate coatings for biomedical applications requiring micropatterned biofunctional surfaces.

Coated Materials, Biocompatible↗
PubMed2006

Cleaning and hydrophilization of atomic force microscopy silicon probes.

The silicon surface of commercial atomic force microscopy (AFM) probes loses its hydrophilicity by adsorption of airborne and package-released hydrophobic organic contaminants. Cleaning of the probes by acid piranha solution or discharge plasma removes the contaminants and renders very hydrophilic probe surfaces. Time-of-flight secondary-ion mass spectroscopy and X-ray photoelectron spectroscopy investigations showed that the native silicon oxide films on the AFM probe surfaces are completely covered by organic contaminants for the as-received AFM probes, while the cleaning methods effectively remove much of the hydrocarbons and silicon oils to reveal the underlying oxidized silicon of the probes. Cleaning procedures drastically affect the results of adhesive force measurements in water and air. Thus, cleaning of silicon surfaces of the AFM probe and sample cancelled the adhesive force in deionized water. The significant adhesive force values observed before cleaning can be attributed to formation of a bridge of hydrophobic material at the AFM tip-sample contact in water. On the other hand, cleaning of the AFM tip and sample surfaces results in a significant increase of the adhesive force in air. The presence of water soluble contaminants at the tip-sample contact lowers the capillary pressure in the water bridge formed by capillary condensation at the AFM tip-sample contact, and this consequently lowers the adhesive force.

Journal Article↗
PubMed2005

Electrochemical release testing of nickel-titanium orthodontic wires in artificial saliva using thin layer activation.

Alloys based on Ni-Ti intermetallics generally exhibit special shape memory and pseudoelastic properties, which make them desirable for use in the dental field as orthodontic wires. The possibility of nickel release from these materials is of high concern, because the allergenicity of this element. The aim of this study was to test pseudoelastic Ni-Ti wires in simulated physiological conditions, investigating the combined effect of strain and fluoridated media: the wires were examined both under strained (5% tensile strain) and unstrained conditions, in fluoridated artificial saliva at 37 degrees C. Real time electrochemical nickel release testing was performed using a novel application of a radiotracer based method, thin layer activation (TLA). TLA was validated, in unstrained conditions, against adsorptive stripping voltammetry methodology. Control tests were also performed in non-fluoridated artificial saliva. From our research it transpired that the corrosion behaviour of Ni-Ti alloy is highly affected by the fluoride content, showing a release of 4.79+/-0.10 microg/cm2/day, but, differently from other biomaterials, it does not seem to be affected by elastic tensile strain. The application of the TLA method in the biomedical field appears a suitable technique to monitor in real time the corrosion behaviour of biomedical devices.

Biomimetic Materials↗
PubMed2005

Tailoring surface properties of biomedical polymers by implantation of Ar and He ions.

Ion implantation at 25 and 100 keV has been used as a tool for the modification of the surface properties of two biomedical polymers. The modulation induced by the different energy dispersion mechanisms of Ar and He have allowed satisfactory modifications for both the activation of the surfaces of chemically functional polycaprolactone (PCL) and the stabilization of anti-fouling poly(ethylene glycol) (PEG). In both cases the implantations have been performed at doses of 10(14) cm(-2) by taking into account the effect of different current densities, which are shown to distinctly influence the fragmentation-crosslinking of the target polymers. The resultant films were characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, time of flight secondary ion mass spectroscopy and atomic force microscopy. Both shifts in zeta potential versus pH curves and the alteration of the polar components of the surface free energy (contact angle measurements) were correlated with the composition analysis. The response of the modified surfaces towards biomolecular interaction is demonstrated by the induction of preferential adsorption on irradiated PCL and the inhibited adsorption onto implanted PEG regions for selected oligopeptides and proteins.

Adsorption↗
PubMed2002

Otolaryngology consultations by real-time telemedicine.

We aimed to assess the value of real-time telemedicine using low cost videoconferencing equipment for otorhinolaryngology consultations. A general practitioner, using low cost videoconferencing equipment, presented patients to an otorhinolaryngologist. After history taking and clinical examination, investigations were requested if required and a diagnosis and management plan formulated. The patients were then seen, by the same otorhinolaryngologist, for a conventional face-to-face consultation. Differences in the history, clinical examination and investigation requests were reported. The accuracy of diagnosis and correlation of management plans between the two consultations were analysed. Forty-three patients were admitted to the study but one, a young child, refused examination either by tele-link or the conventional approach and had to be excluded. There were thus 42 patients with 55 diagnoses included in the trial, 26 (62%) females and 16 (38%) males. Age range was 5 months to 70 years. There was no difficulty with any of the patients in obtaining an accurate history and ordering investigations, if required, via the telelink. Clinical examination during the tele-link consultation was inadequate for eight out of the first 20 patients, resulting in a wrong diagnosis in three patients and a missed diagnosis in five patients. All of the next 22 patients had a correct diagnosis and management plan. Comparison of data from the two types of consultation showed that a correct diagnosis and management plan was made in 34 patients. Low cost real-time telemedicine is a useful technique, providing reliable otorhinolaryngology consultations in a general practice setting. However initial difficulties due to inexperience in using the equipment need to be overcome.

Adolescent↗
PubMed2000

Radioactivity measurements for the thin layer activation technique

Thin layer activation (TLA) is one of the promising techniques employing radiotracers at low levels of radioactivity for material performance studies such as wear and corrosion. The principle of TLA is the creation of an appropriate radionuclide in a given material to a well defined depth of a selected area. This activation is realised by exposure of the component to a charged particle beam using, e.g., a cyclotron facility. If the material is subjected to mechanical or chemical degradation, any loss of the activated material will result in a loss in radioactivity of the activated component. The sensitivity of TLA technique is high due to the capability of low level radioactivify measurement performed by gamma spectrometry. The sensitivity of TLA is below 0.1 microm thickness loss or 1 ng mass loss. In the present paper, some applications of TLA in ongoing research at the Institute for Health and Consumer Protection of the European Commission are presented.

Journal Article↗
PubMed1999

Comprehensive evaluation of isoprenoid biosynthesis regulation in Saccharomyces cerevisiae utilizing the Genome Reporter Matrix.

Gene expression profiling is rapidly becoming a mainstay of functional genomic studies. However, there have been relatively few studies of how the data from expression profiles integrate with more classic approaches to examine gene expression. This study used gene expression profiling of a portion of the genome of Saccharomyces cerevisiae to explore the impact of blocks in the isoprenoid biosynthetic pathway on the expression of genes and the regulation of this pathway. Approximately 50% of the genes whose expression was altered by blocks in isoprenoid biosynthesis were genes previously known to participate in the pathway. In contrast to this simple correspondence, the regulatory patterns revealed by different blocks, and in particular by antifungal azoles, was complex in a manner not anticipated by earlier studies.

Base Sequence↗
PubMed1997

Risk factors for recurrence of hemorrhagic endovasculitis of the placenta.

OBJECTIVE: To assess the potential for recurrence of placental hemorrhagic endovasculitis and to identify clinical or pathologic cofactors that might influence recurrence of this lesion or subsequent pregnancy outcome. METHODS: Ninety-seven women with a placenta affected by hemorrhagic endovasculitis, who also had at least one placenta referred to the Michigan Placental Tissue Registry from a subsequent pregnancy, were identified from 10,531 referrals between 1978 and 1988. Histologic slides from 209 placentas and clinical data from 211 infants (two sets of twins) from initial (first) and subsequent referrals were analyzed. Placentas were graded for the presence, extent, and severity of hemorrhagic endovasculitis and chronic villitis of unknown etiology; for placental lesions indicative of hypertensive maternal vessel disease; and for intravascular nucleated erythrocytes and chorionic thrombi. Maternal data included age, gravidity, number of previous losses, and history of toxemia or hypertension. All data were analyzed for significance using chi2 and t tests. Outcome assessment was based on recurrence of hemorrhagic endovasculitis and infant viability with the second referral. RESULTS: With first referrals, 80 of 98 infants (81.6%) were stillborn. Among second referrals, 26 of 98 infants (26.5%) were stillborn. Hemorrhagic endovasculitis recurred in 28 second placentas (28.9%); of these, 18 infants (64.3%) were stillborn. Higher rates of recurrence were found with progressively higher first-referral chronic villitis severity scores (P < .02), higher hypertensive placental lesion scores (P < .001), and first referrals with a history of toxemia or hypertension (P < .02). Recurrence of hemorrhagic endovasculitis was higher in patients with two or more of these factors in first referrals (P < .001). Subsequent stillbirth was more frequent with progressively higher first-referral hypertensive placental lesion scores (P < .01) and in first placentas with two or more risk factors (P = .064). Hemorrhagic endovasculitis severity scores, intravascular nucleated erythrocytes, and chorionic thrombi were associated with stillbirth in index pregnancies only. Maternal age, gravidity, or history of prior losses were not predictive. CONCLUSIONS: Placental hemorrhagic endovasculitis is associated with pregnancy loss and can recur in some patients. Interrelations among placental hemorrhagic endovasculitis, chronic villitis, maternal hypertension, and adverse outcomes in subsequent pregnancies are apparent. This information may be useful in patient counseling.

Adolescent↗
PubMed1996

Plasma alpha-tocopherol concentrations after supplementation with water- and fat-soluble vitamin E.

The objective of this study was to examine differences in plasma alpha-tocopherol concentrations after oral administration of pharmacologic doses of vitamin E to normal healthy subjects as RRR-alpha-tocopheryl glycol 1000 succinate (TPGS; water-miscible form) and RRR-alpha-tocopheryl acetate (TA; fat-soluble form). The study was designed to evaluate the administration of three different single doses and multiple doses for 4 wk with both preparations. Administration of 400 IU (269 mg), 800 IU (537 mg), and 1200 IU (807 mg) TPGS as a single dose resulted in slight elevation of plasma alpha-tocopherol concentrations. Administration of multiple daily doses at all three amounts of TPGS for 28 consecutive days resulted in a slight elevation of plasma alpha-to-copherol concentrations. A significant increase in plasma alpha-to-copherol concentrations was observed after ingestion of a single dose or equivalent multiple doses of TA at all three doses. As reported in the literature, in cases of cholestasis and other forms of lipid malabsorption, oral administration of TPGS is the treatment of choice. It appears that for normal adults and patients with normal lipid absorption, fat-soluble forms of vitamin E are preferable for therapeutic and prophylactic uses.

Adult↗
PubMed1992

The bactericidal activity of a methyl and propyl parabens combination: isothermal and non-isothermal studies.

The effect of temperature on the kill rate of Escherichia coli by methyl and propyl parabens was studied. The kill kinetics was first order. It was shown that the Arrhenius equation provided a good model for describing the relationship between the first order rate constant and the temperature. The activation energy was found to be 274 kJ/mol for exponential phase cells and 168 kJ/mol for stationary phase cells. Exponential phase cells were much more susceptible to the lethal effects of the parabens than were the stationary phase cells. For example, at 34 degrees C stationary phase cells, in chemically defined media, had a kill rate constant of 0.072/h while the corresponding value for exponential phase cells was 0.238/h. In water the rate of kill for exponential phase cells was even faster giving a rate constant of 5.25/h at 34 degrees C. Non-isothermal kinetic testing was not found to be useful for modelling bacterial kill kinetics because we could not achieve the precision required in bacterial enumeration.

Culture Media↗
PubMed1992

Kinetic evaluation of claimed synergistic paraben combinations using a factorial design.

The antimicrobial effects of methyl and propyl parabens are investigated, with Escherichia coli as test organism, with a view to determining whether the parabens act synergistically. At appropriate concentrations, the parabens killed E. coli cells according to first order kinetics and the bactericidal effects were quantified by the first order kill rate constants. Combinations of methyl or propyl parabens, at concentrations which slow down or inhibit bacterial growth when used singly, produced definite kill. In this sense, the parabens are therefore synergistic since in combination they produce an effect which is not observed when they are used singly. This effect is not true synergism as shown by the results of our experiments with a factorial design. Analysis of variance indicated no significant interaction between the two parabens.

Analysis of Variance↗
PubMed1991

Plasma tocopherol concentrations in response to supplemental vitamin E.

Normal healthy volunteers were studied after various doses of dl-alpha-tocopherol were ingested on different schedules. Administration of 440, 880, or 1320 mg (400, 800, or 1200 IU) of dl-alpha-tocopherol as a single dose resulted in elevation of plasma alpha-tocopherol concentrations that peaked at 12-24 h. Chronic administration of dl-alpha-tocopherol (440, 880, or 1320 mg/d for 28 d) resulted in a steady state that occurred by days 4-5 of supplementation. Discontinuation of the treatment after day 28 was associated with a decline of plasma alpha-tocopherol, which returned to the pretreatment concentrations between 12 and 20 d. The plasma elevation of alpha-tocopherol was affected by dietary fat intake. Individuals consuming a high-fat diet showed significantly greater plasma alpha-tocopherol concentrations as compared with those fed a low-fat diet. The results of this study indicate that plasma kinetics of alpha-tocopherol are similar when supplements of 440, 880, or 1320 mg dl-alpha-tocopherol are given to normal, healthy individuals.

Adult↗
PubMed1990

Alteration of retinol-binding-protein concentrations by the synthetic retinoid fenretinide in healthy human subjects.

Normal subjects received fenretinide (HPR), 200 mg/d, on three schedules. Schedule 1 was treatment for 28 d. Schedule 2 consisted of 14 d of treatment, 3 d hiatus, and a second drug course of 14 d, 10,000 IU vitamin A was administered during the 3-d hiatus. Schedule 3 was 14 d of treatment followed by a rest period of 7 d and then 14 d of treatment. Increase in plasma HPR was accompanied by an even higher increase in the metabolite N-(4-methoxyphenyl)-all-trans-retinamide (MPR). The administration of HPR was associated with a significant reduction in retinol-binding protein (RBP), which returned to pretreatment values after the drug treatment was discontinued. Reduction of plasma retinol was also observed. Use of interrupted schedules with resting periods of 3 and 7 d changed HPR, MPR, and RBP concentrations in plasma. Addition of vitamin A did not affect the pattern of the measured variables in the plasma.

Adult↗