PubMed Health⌕ Search

Biomedical subjects

A McKinnon

Publications and source records attributed to A McKinnon.

15 recordsLinked to original sources
PubMed2004

Strong polarization in the optical transmission through elliptical nanohole arrays.

Strong polarization dependence is observed in the optical transmission through nanohole arrays in metals. It is shown that the degree of polarization is determined by the ellipticity and orientation of the holes; the polarization axis lies perpendicular to the broad edge of the ellipse. Furthermore, the depolarization ratio shows a squared dependence on the aspect ratio of the holes, which is discussed in terms of coupling into and out of the surface plasmon modes. The observed results will be useful for tailoring the polarization behavior of metallic nanophotonic elements in many applications, including surface plasmon enhanced optical sensing and ultrafast optical switching.

Journal Article↗
PubMed2001

At the solid/liquid interface: FTIR/ATR--the tool of choice.

For the last 7 years, we have been researching various aspects of the Bayer process. Predominant among these has been the surface chemistry of Bayer process solids. To this end, we have been using Fourier transform infrared (FTIR) attenuated total reflection (ATR) spectroscopy for in situ studies of the surfaces of the Bayer process solids sodium oxalate and aluminium trihydroxide under extreme (high ionic strength, high pH), Bayer-like conditions. FTIR/ATR is one of the few techniques currently available to scientists wishing to explore solid/liquid interfacial phenomena in situ. Using this investigative technique, information regarding the nature of adsorbed species can be readily acquired, with details concerning adsorbate orientation and adsorption/desorption equilibria, speciation, mechanisms and kinetics obtainable. Not surprisingly, FTIR/ATR has become one of the tools of choice for those wishing to explore the solid/liquid interface, and the body of literature available on the subject has been steadily growing over the last 10-15 years. This review addresses the current state of knowledge in the area of FTIR/ATR with respect to interfacial spectroscopy, as well as introducing some of the more fundamental theoretical and practical aspects of the technique. Particular emphasis is placed upon applied interfacial research. In writing this review, we draw on a considerable amount of expertise in the use of FTIR/ATR in interfacial studies (in particular, the practical considerations involved), as well as a large and comprehensive literature database focussing primarily on the investigation of interfacial processes using the FTIR/ATR technique.

Aluminum Hydroxide↗
PubMed1999

Are you ready (to be a neuroscience nurse)?

On the pediatric neurosciences unit of British Columbia's Children's Hospital we are in the throes of a nursing staff crisis. In the last year alone we hired ten new graduates to work as casuals on our unit. With a two and a half day hospital orientation, five preceptor shifts, and a Competency Based Education Plan in hand, we send them off to the trenches. We know these nurses have little nursing experience and even less Neuroscience nursing experience. Yet, we expect them to care for patients and families whose problems they may not understand. For a preceptor, and senior colleague, this is a disturbing situation. We recognize that in their orientation shifts they have not even begun to experience the challenges of a Neuroscience unit. Have they cared for a child who has had a postoperative laminectomy? Do they recognize subtle seizures? Have they sat with a family who have just learned that their child has a brain tumor? No. We expect them to care for patients and families with minimal support. This is the reality of nursing today. Many of us pride ourselves on being committed pediatric Neuroscience nurses. Our physicians rely upon our assessment skills and they trust our intuition! We believe we have earned that trust. How can we convey our enthusiasm and excitement to our perceptees so they are motivated to stay and become experienced pediatric Neuroscience nurses? In this presentation we outline our paper to remedy this situation.

Career Choice↗
PubMed1994

Biliary dilatation in asymptomatic AIDS patients.

Cytomegalovirus (CMV) is a recognized cause of biliary abnormalities in acquired immune deficiency syndrome (AIDS) patients. In a prospective trial, two of 25 (8%) of AIDS patients on treatment for CMV related infections without biliary symptoms were found to have biliary dilatation on ultrasound. The study confirms previous findings of the poor correlation of sonographic findings with clinical status and biochemical profiles, and demonstrates that biliary tree dilatation in this group of patients may not per se warrant further invasive investigation.

AIDS-Related Opportunistic Infections↗
PubMed1993

Nasal administration of retinal antigens suppresses the inflammatory response in experimental allergic uveoretinitis. A preliminary report of intranasal induction of tolerance with retinal antigens.

Current immunotherapy of posterior uveitis is non-specific and limited by drug toxicity and unpredictable relapses on therapy. Alternative modes of therapy being investigated using the rat model of experimental autoimmune uveoretinitis (EAU) have included the induction of tolerance with oral administration of milligram quantities of retinal antigens. In this preliminary report we demonstrate that tolerance to retinal antigens can be induced via the upper respiratory tract with microgram doses of antigen, preventing subsequent induction of EAU.

Animals↗
PubMed1992

Patterns of angiogenic response to mast cell granule constituents.

Agents derived from mast cell granule constituents, and compound 48/80 which stimulates release of mast cell granules, have been used by us to develop new methods for quantitating angiogenesis in the chick chorioallantoic membrane. Two of these methods provide different insights, demonstrating different patterns of response to dosage and over time, produced by different agents. Counting mesenchymal blood vessels is convenient for obtaining dose-response data. Histamine and compound 48/80 have been shown previously to give a sigmoid dose-response curve resulting in a plateau before the lethal dose. This contrasts with the effect of porcine sodium heparin (Evans Biologicals) which results in a minor increase then a relative decline in vessel number due to a failure of growth. Here, the ability to produce angiogenesis or antiangiogenesis appears to be dose-dependent. Measurement of the changes in DNA synthesis, leading to visible angiogenesis, may be performed once the optimal angiogenic dose is known, and again distinctive patterns of response with different agents have been found. Histamine results in a fall then rise to a peak at 36 hr. We now show that two types of heparin each produce a peak at 12 hr. Compound 48/80 results in a distinctive pattern that looks like a composite of the histamine and especially the heparin effects, and this suggests that both are relevant to induction of angiogenesis by mast cells. The elicitation of this pattern of response also provides a method, additional to electron microscopy, for discovering whether or not an angiogenic substance is likely to operate via mast cell stimulation. Such characteristic patterns offer a new way of classifying angiogenic substances.

Animals↗
PubMed1991

Ultrastructural pathology of the 'barrier sites' in experimental autoimmune uveitis and experimental autoimmune pinealitis.

Lewis rats were immunised with retinal S-antigen to induce experimental autoimmune uveitis and experimental autoimmune pinealitis. The blood-retinal and blood-pineal 'barrier sites' were examined by transmission electron microscopy. Inflammatory cell movement through Bruch's membrane involved separation of its constituent layers, cell migration through pores in the membrane, and between retinal pigment epithelial cells without causing significant displacement of the retinal pigment epithelial cell layer. The endothelial cells of retinal and pineal vessels with perivascular infiltrates showed morphological features resembling endothelium of 'high endothelial venules'.

Animals↗
PubMed1991

Structure-function studies of S-antigen: use of proteases to reveal a dominant uveitogenic site.

Retinal S-antigen induced experimental autoimmune uveitis (EAU) is a severe, predominantly T-cell mediated inflammatory disease of the uveal tract and retina of the eye. Pretreatment of LEW rats with the monoclonal antibody, MAbS2.4.C5, which defines an epitope in S-antigen, has been shown to effectively inhibit the subsequent induction of EAU with S-antigen. Using synthetic peptides and cyanogen bromide fragments of S-antigen we found the binding site of MAbS2.4.C5 to be located at the carboxy terminus of the molecule corresponding to amino acid positions 375 to 380. Limited Staphylococcus aureus V8 protease digestion yielded several polypeptide fragments including one large 43 kD fragment which retained antibody binding to a variety of both polyclonal and monoclonal antibodies which identify epitopes that span the length of the S-antigen. This treatment, however, completely destroys the MAbS2.4.C5 binding site and dramatically reduces uveitopathogenicity. Limited trypsin and papain digestion, on the other hand, had little effect on pathogenicity or on MAbS2.4.C5 binding to S-antigen or its peptide fragments. These results indicate that the carboxy-terminus of S-antigen plays a predominant role in the pathogenesis of EAU.

Amino Acid Sequence↗
PubMed1989

The influence of adaptive seating devices on vocalization.

This study examined the relationship between receipt of adaptive seating devices (ASD) and sophistication of early vocalizations/verbalizations. Eight nonverbal children with cerebral palsy were studied prior to and following receipt of an ASD. Total speech tokens increased for 7 of the 8 subjects and diversity of speech sounds increased for 6 subjects. A concomitant improvement in feeding independence was observed for those subjects who demonstrated the greatest increase in speech sound diversity.

Cerebral Palsy↗
PubMed1985

High-performance liquid chromatographic analysis of basic drugs on silica columns using non-aqueous ionic eluents. II. Application of UV, fluorescence and electrochemical oxidation detection.

Unmodified silica columns together with non-aqueous ionic eluents give stable yet flexible systems for the analysis of basic drugs by high-performance liquid chromatography. Low-wavelength UV and fluorescence detection may be used, and fluorescence may be optimised by, for example, post-column pH change or derivatisation of some primary aliphatic amines with o-phthaldialdehyde. A novel feature is that electrochemical oxidation can be used for the detection of most analytes and this detection mode is thus discussed in detail. Retention and relative response data (UV, 254 nm and electrochemical, +1.2 V) have been generated for 462 compounds using a 125-mm Spherisorb S5W silica column and methanolic ammonium perchlorate (10 mM, pH 6.7) as eluent. This system can be used isocratically in qualitative analyses and also for quantitative work, when either the wavelength or the applied potential can be adjusted to optimise the response.

Chromatography, High Pressure Liquid↗