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Biomedical subjects

A Rodger

Publications and source records attributed to A Rodger.

At least 19 recordsLinked to original sources
PubMed2002

Gas chromatography: an investigative tool in multiple allergies to essential oils.

Essential or fragrant oils are volatile odourous mixtures of organic chemical compounds that are widely used in aromatherapy and in the perfume industry. Because of their frequent use, allergy to essential oils is being increasingly recognized. We report 2 cases of multiple allergies to essential oils in professional aromatherapists. Gas chromatography/mass spectrometry was used to analyse the oils in order to identify a common allergen responsible for the contact dermatitis. In both the cases, alpha- and beta-pinene were found to be the most common constituent in the oils and thus appeared to be key allergens. alpha-pinene was confirmed as an allergen on repeat patch testing with pure alpha-pinene in both cases. 12 controls tested were negative for the same. Gas chromatography-mass spectrometry was found to be an extremely useful tool that could be utilized in investigating multiple allergies to essential oils.

Allergens↗
PubMed2001

Linear dichroism for the detection of single base pair mutations.

Flow linear dichroism is shown to be able to detect single base mismatches in a polymerase chain reaction (PCR) amplimers from exon 10 of the human beta-glucocerebrosidase gene (associated with Gaucher disease) over a kilobase long with no post PCR manipulation.

Alleles↗
PubMed2001

Distinct Albino3-dependent and -independent pathways for thylakoid membrane protein insertion.

The homologous proteins Oxa1, YidC, and Alb3 mediate the insertion of membrane proteins in mitochondria, bacteria, and chloroplast thylakoids, respectively. Depletion of YidC in Escherichia coli affects the integration of every membrane protein studied, and Alb3 has been shown previously to be required for the insertion of a signal recognition particle (SRP)-dependent protein, Lhcb1, in thylakoids. In this study we have analyzed the "global" role of Alb3 in the insertion of thylakoid membrane proteins. We show that insertion of two chlorophyll-binding proteins, Lhcb4.1 and Lhcb5, is almost totally blocked by preincubation of thylakoids with anti-Alb3 antibodies, indicating a requirement for Alb3 in the insertion pathway. Insertion of the related PsbS protein, on the other hand, is unaffected by Alb3 antibodies, and insertion of a group of SRP-independent, signal peptide-bearing proteins, PsbX, PsbW, and PsbY, is likewise completely unaffected. Proteinase K is furthermore able to completely degrade Alb3, but this treatment does not affect the insertion of these proteins. Among the thylakoid proteins studied here, Alb3 requirement correlates strictly with a requirement for stromal factors and nucleoside triphosphates. However, the majority of proteins tested do not require Alb3 or any other known form of translocation apparatus.

Arabidopsis Proteins↗
PubMed2001

Estrogen-derived steroidal metal complexes: agents for cellular delivery of metal centers to estrogen receptor-positive cells.

Targeted cellular delivery of drugs to specific tissues is an important goal in biomedical chemistry. Achieving this requires harnessing and applying molecular-level recognition events prevalent in (or specific to) the desired tissue type. Tissues rich in estrogen receptors (ERs), which include many types of breast cancer, accumulate molecules that have high binding affinities for these receptors. Therefore, molecules that (i) bind to the ER, (ii) have favorable cellular transport properties, and (iii) contain a second functionality (such as a center that may be used for diagnostic imaging or medical therapy) are exciting synthetic targets in the field of drug delivery. To this end, we have prepared a range of metallo-estrogens based on 17alpha-ethynylestradiol and examined their binding to the ER both as isolated receptor and in whole cell assays (ER positive MCF-7 cells). Estrogens functionalized with metal binding units are prepared by palladium-catalyzed cross-coupling reactions and a wide range of metal centers introduced readily. All the compounds prepared and tested exhibit effective binding to the estrogen receptor and are delivered across the cell membrane into MCF-7 cells. In the whole cell assays, despite their monocationic nature, the palladium and platinum complexes prepared exhibit similar (and even enhanced) receptor binding affinities compared to their corresponding neutral free ligands. It is unprecedented for a higher ER binding affinity to be observed for a cationic complex than for its metal-free ligand.

Biological Transport↗
PubMed2001

Conformation of a purified "spontaneously" inserting thylakoid membrane protein precursor in aqueous solvent and detergent micelles.

Subunit W of photosystem II (PsbW) is a single-span thylakoid membrane protein that is synthesized with a cleavable hydrophobic signal peptide and integrated into the thylakoid membrane by an apparently spontaneous mechanism. In this study, we have analyzed the secondary structure of the pre-protein at early stages of the insertion pathway, using purified recombinant pre-PsbW. We show that the protein remains soluble in Tris buffer after removal of detergent. Under these conditions pre-PsbW contains no detectable alpha-helix, whereas substantial alpha-helical structure is present in SDS micelles. In aqueous buffer, the tryptophan fluorescence emission characteristics are intermediate between those of solvent-exposed and hydrophobic environments, suggesting the formation of a partially folded structure. If denaturants are excluded from the purification protocol, pre-PsbW purifies instead as a 180-kDa oligomer with substantial alpha-helical structure. Mature-size PsbW was prepared by removal of the presequence, and we show that this protein also contains alpha-helix in detergent but in lower quantities than the pre-protein. We therefore propose that pre-PsbW contains alpha-helical structure in both the mature protein and the signal peptide in nonpolar environments. We propose that pre-PsbW acquires its alpha-helical structure only during the later, membrane-bound stages of the insertion pathway, after which it forms a "helical hairpin"-type loop intermediate in the thylakoid membrane.

Chromatography, Gel↗
PubMed2001

A double exposed portal image comparison between electronic portal imaging hard copies and port films in radiation therapy treatment setup confirmation to determine its clinical application in a radiotherapy center.

PURPOSE: At the William Buckland Radiotherapy Center (WBRC), field-only electronic portal image (EPI) hard copies are used for radiation treatment field verification for whole brain, breast, chest, spine, and large pelvic fields, as determined by a previous study. A subsequent research project, addressing the quality of double exposed EPI hard copies for sites where field only EPI was not considered adequate to determine field placement, has been undertaken. The double exposed EPI hard copies were compared to conventional double exposed port films for small pelvic, partial brain, and head and neck fields and for a miscellaneous group. METHODS AND MATERIALS: All double exposed EPIs were captured during routine clinical procedures using liquid ion chamber cassettes. EPI hard copies were generated using a Visiplex multi-format camera. In sites where port film remained the preferred verification format, the port films were generated as per department protocol. In addition EPIs were collected specifically for this project. Four radiation oncologists performed the evaluation of EPI and port film images independently with a questionnaire completed at each stage of the evaluation process to assess the following: Adequacy of information in the image to assess field placement. Adequacy of information for determining field placement correction. Clinician's preferred choice of imaging for field placement assessment RESULTS: The results indicate that double exposed EPI hard copies generally do containsufficient information to permit evaluation of field placement and can replace conventionaldouble exposed port films in a significant number of sites. These include the following:pelvis fields < 12 X 12 cm, partial brain fields, and a miscellaneous group. However forradical head and neck fields, the preferred verification image format remained port film dueto the image hard copy size and improved contrast for this media. Thus in this departmenthard copy EPI is the preferred modality of field verification for all sites except radical headand neck treatments. This should result in an increase in efficiency of workloadmanagement and patient care.

Head and Neck Neoplasms↗
PubMed2001

HIV seroconverters: using surveillance to characterise people with incident HIV infection in Victoria, Australia.

This paper describes a cohort of people living in Victoria, Australia, diagnosed with incident HIV infection and identified through routine HIV surveillance. All HIV diagnoses notified to the Victorian HIV Registry between January 1997 and September 1998 were included. Infections were classified as incident if there was a prior negative test and/or seroconversion illness within 12 months of the first positive HIV test. During the study period there were 277 notifications received of which 70 (25%) were incident infections (seroconversions). People with incident infection were aged 36 years (+/- 10), from an Anglo background (76%) and living in Melbourne (91%). Seroconverters were more likely to have acquired their infection in Victoria (76%), through male-to-male sexual contact (86%), and from casual or anonymous partners (67%). Cohorts of individuals with incident HIV infection provide a valuable resource for understanding the dynamics of HIV acquisition and natural history of the infection.

Adult↗
PubMed2001

Dialysis cells for controlled DNA: drug binding studies.

An efficient small volume accurate dialysis system has been designed, built and tested for proflavine binding to DNA based upon the side by side design used in the Franz diffusion cell. In a typical experiment 3 cm3 of DNA solution is added to one side and 3 cm3 of ligand to the other with a dialysis membrane between the two sides of 1 cm in diameter, thereby minimizing the area of dialysis membrane that the solutions are in contact with.

Animals↗
PubMed2001

Establishing an evidence base for the specialist breast nurse: a model for Australian breast cancer care.

The unmet needs of women with breast cancer have been extensively documented. In the United Kingdom, the introduction of the specialist breast nurse (SBN) role has been one strategy to improve the psychological wellbeing of women. This paper describes a SBN model of care and clinical pathway for Australian treatment settings, developed from systematic reviews of research and clinical practice guidelines for the treatment and psychosocial care of women with breast cancer. The model acknowledges the SBN as an integral member of the multi-disciplinary team with a key role to meet the emotional and informational needs of women diagnosed with breast cancer from the time of diagnosis through to follow up after treatment.

Australia↗
PubMed2001

Tracing and recruiting a cohort with community acquired hepatitis 25 years later.

OBJECTIVE: We describe the methods used to trace and recruit a cohort (including injecting drug users) 25 years after admission to hospital in Melbourne with hepatitis. METHODS: Information recorded in the original medical record was used for tracing purposes. Subjects were located using the electoral roll, CD-ROM telephone directory, the Health Insurance Commission database, Hepatitis Foundation newsletters, advertising and features in the press and local radio. Other approaches included contacting local medical officer or next of kin from the original admission, and the National Death Registry. RESULTS: Tracing was undertaken on all members of the cohort; two-thirds were located. Methods were applied sequentially and 36% were found by CD-ROM telephone directory and the electoral roll, 33% from Health Insurance records, 15% by letter to last known address, 10% from contact of original next of kin, 3% from radio publicity and 1% from media advertisements. Of those who were located, 85% participated in the study. CONCLUSIONS: Accurate ascertainment of birth date and full name from original case records was essential for tracing purposes. Use of Health Insurance records and CD-ROM telephone directory and the electoral roll were the most successful means of locating subjects while newspaper advertising was non-productive and expensive. History of IDU was the major association with failure to trace and unwillingness to enrol, but despite this tracing and recruitment was high in this group. The high participation rate in those located appears to be due to the experience of the staff member making the initial contact.

Adult↗
PubMed2000

Sticky-end assembly of a designed peptide fiber provides insight into protein fibrillogenesis.

Coiled-coil motifs provide simple systems for studying molecular self-assembly. We designed two 28-residue peptides to assemble into an extended coiled-coil fiber. Complementary interactions in the core and flanking ion-pairs were used to direct staggered heterodimers. These had "sticky-ends" to promote the formation of long fibers. For comparison, we also synthesized a permuted version of one peptide to associate with the other peptide and form canonical heterodimers with "blunt-ends" that could not associate longitudinally. The assembly of both pairs was monitored in solution using circular dichroism spectroscopy. In each case, mixing the peptides led to increased and concentration-dependent circular dichroism signals at 222 nm, consistent with the desired alpha-helical structures. For the designed fiber-producing peptide mixture, we also observed a linear dichroism effect during flow orientation, indicative of the presence of long fibrous structures. X-ray fiber diffraction of partially aligned samples gave patterns indicative of coiled-coil structure. Furthermore, we used electron microscopy to visualize fiber formation directly. Interestingly, the fibers observed were at least several hundred micrometers long and 20 times thicker than expected for the dimeric coiled-coil design. This additional thickness implied lateral association of the designed structures. We propose that complementary features present in repeating structures of the type we describe promote lateral assembly, and that a similar mechanism may underlie fibrillogenesis in certain natural systems.

Amino Acid Motifs↗
PubMed2000

DNA structure control by polycationic species: polyamine, cobalt ammines, and di-metallo transition metal chelates.

Many polycationic species bind to DNA and induce structural changes. The work reported here is the first phase of a program whose long-term aim is to create a class of simple and inexpensive sequence-selective compounds that will enable enhanced DNA structure control for a wide range of applications. Three classes of molecule have been included in this work: the polyamine spermine (charge: 4(+)) and spermidine (charge: 3(+)) (which are known to induce a wide range of DNA conformational changes but whose binding modes are still not well understood); cobalt (III) amine transition metal complexes as potential polyamine mimics and [Fe(H(2)O)(6)](3+); and the first member of a new class of di-metallo tris-chelated cylinders of helical structure (charge 4(+)). Temperature-dependent absorption, circular dichroism, linear dichroism, gel electrophoresis, and molecular modeling data are presented. The cobalt amines prove to be effective polyamine mimics, although their binding appears to be restricted to backbone and major groove. All the ligands stabilize the DNA, but the 4(+) di-iron tris-chelate does so comparatively weakly and seems to have a preference for single-stranded DNA. All the molecules studied bend the DNA, with the di-iron tris-chelate having a particularly dramatic effect even at very low drug load.

Chelating Agents↗
PubMed2000

Management of the axilla in operable breast cancer treated by breast conservation: a randomized clinical trial. Edinburgh Breast Unit.

BACKGROUND: In the treatment of operable breast cancer by breast conservation, the extent of axillary dissection, the need for radiotherapy to the axilla and the morbidity associated with these procedures have not been assessed adequately. METHODS: Patients with operable breast cancer were randomized to have level III axillary node clearance (232 patients) or axillary node sample (234 patients). Radiotherapy to the axilla was given selectively. Radiotherapy was not given to those who had an axillary clearance. In the early part of the study all patients who had node sample were treated by radiotherapy (54 patients); subsequently this was modified to include only those who were node positive. The morbidity to the shoulder and arm was assessed before and after operation by measuring upper limb volume and circumference, and combined glenohumeral and scapular movement and muscle power. RESULTS: Comparing the two surgical policies, no difference was found in local (axillary clearance 14 versus sample 15), axillary (eight versus seven) or distant (29 versus 29) recurrence. There was no statistically significant difference in 5-year survival rate (clearance 82.1 versus sample 88.6 per cent). Morbidity was least in those who had a node sample and no radiotherapy to the axilla. Radiotherapy to the axilla in patients who had a node sample resulted in a significant reduction in range of movement of the shoulder, e.g. mean(s.e.) 2.2(0.6) cm reduction in lateral rotation at 3 years. Surgical axillary clearance was associated with significant lymphoedema of the upper limb, e.g. 4.1(0.7) per cent increase in arm volume at 3 years. CONCLUSION: A selective policy for the management of the axilla is associated with no increase in axillary recurrence or mortality rate compared with routine axillary node clearance. Patients who are node negative after axillary sample can avoid radiotherapy or axillary clearance.

Aged↗