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Biomedical subjects

A Elliott

Publications and source records attributed to A Elliott.

At least 19 recordsLinked to original sources
PubMed1998

Fine localization of the Nijmegen breakage syndrome gene to 8q21: evidence for a common founder haplotype.

Nijmegen breakage syndrome (NBS) is a rare autosomal recessive disorder characterized by microcephaly, a birdlike face, growth retardation, immunodeficiency, lack of secondary sex characteristics in females, and increased incidence of lymphoid cancers. NBS cells display a phenotype similar to that of cells from ataxia-telangiectasia patients, including chromosomal instability, radiation sensitivity, and aberrant cell-cycle-checkpoint control following exposure to ionizing radiation. A recent study reported genetic linkage of NBS to human chromosome 8q21, with strong linkage disequilibrium detected at marker D8S1811 in eastern European NBS families. We collected a geographically diverse group of NBS families and tested them for linkage, using an expanded panel of markers at 8q21. In this article, we report linkage of NBS to 8q21 in 6/7 of these families, with a maximum LOD score of 3.58. Significant linkage disequilibrium was detected for 8/13 markers tested in the 8q21 region, including D8S1811. In order to further localize the gene for NBS, we generated a radiation-hybrid map of markers at 8q21 and constructed haplotypes based on this map. Examination of disease haplotypes segregating in 11 NBS pedigrees revealed recombination events that place the NBS gene between D8S1757 and D8S270. A common founder haplotype was present on 15/18 disease chromosomes from 9/11 NBS families. Inferred (ancestral) recombination events involving this common haplotype suggest that NBS can be localized further, to an interval flanked by markers D8S273 and D8S88.

Chromosome Breakage↗
PubMed1998

Low level CO2 effects on pulmonary function in humans.

The purpose of the study was to determine whether chamber exposure to low levels of CO2 results in functional alterations in gas mixing and closing volume in humans. Four healthy volunteer subjects were exposed to 0.7% CO2 and to 1.2% CO2. Spirometry, lung volumes, single breath nitrogen washout, diffusing capacity for carbon monoxide (DLCO) by two methods, and cardiac output were measured in triplicate. Values were obtained over two non-consecutive days during the training period (control) and on days 2 or 3, 4, 6, 10, 13, and 23 of exposure to each CO2 level. Measurements were made during the same time of day. There was one day of testing after exposure, while still in the chamber but off carbon dioxide. The order of testing, up until measurements of DLCO and cardiac output, were randomized to avoid presentation effects. The consistent findings were a reduction in diffusing capacity for carbon monoxide and a fall in cardiac output, occurring to a similar degree with both exposures. For the group as a whole, there was no indication of major effects on spirometry, lung volumes, gas mixing or dead space. We conclude that small changes may occur in the function of distal gas exchanging units; however, these effects were not associated with any adverse health effects. The likelihood of pathophysiologic changes in lung function or structure with 0.7 or 1.2% CO2 exposure for this period of time, is therefore, low.

Breath Tests↗
PubMed1997

Intracellular alkalinization mobilizes calcium from agonist-sensitive pools in rat lacrimal acinar cells.

1. We have investigated interactions between intracellular pH (pHi) and the intracellular free calcium concentration ([Ca2+]i) in collagenase-isolated rat lacrimal acinar cells. The fluorescent dyes fura-2 and 2',7'-bis(carboxyethyl)-5-carboxyfluorescein (BCECF) were used to measure [Ca2+]i and pHi, respectively. 2. Application of the weak base NH4Cl alkalinized the cytosol and caused a dose-dependent increase in [Ca2+]i. Trimethylamine (TMA) also alkalinized the cytosol and increased [Ca2+]i. The increase in [Ca2+]i evoked by NH4Cl or TMA was much smaller than that evoked by the secretory agonist acetylcholine (ACh). 3. Application of NH4Cl also increased [Ca2+]i in cells bathed in Ca(2+)-free medium, indicating that NH4Cl released Ca2+ from an intracellular pool. 4. Ammonium chloride had no effect on [Ca2+]i in cells bathed in Ca(2+)-free medium if agonist-sensitive intracellular Ca2+ pools had been depleted with either ACh or the microsomal Ca(2+)-ATPase inhibitor 2,5-di(tert-butyl)hydroquinone. Treatment of cells with NH4Cl in Ca(2+)-free medium reduced the amount of Ca2+ released by ACh. These results suggest that NH4Cl released Ca2+ from the same intracellular pool released by ACh. 5. Calcium release from the agonist-sensitive pool was also triggered when the cytosol was alkalinized by removing the weak acid acetate. 6. Ammonium chloride caused a modest increase in inositol phosphate production, suggesting that NH4Cl may have released stored Ca2+ via an increase in the intracellular inositol 1,4,5-trisphosphate concentration. 7. The increase in [Ca2+]i evoked by NH4Cl was not sustained even in the presence of extracellular Ca2+. In contrast, when a low dose of ACh was used to evoke intracellular Ca2+ release of similar magnitude, sustained Ca2+ entry was observed. 8. Alkalinizing the cytosol appeared to partially inhibit Ca2+ entry triggered by thapsigargin or by ACh. 9. We suggest that alkalinizing the cytoplasm in unstimulated lacrimal acinar cells can release Ca2+ from the intracellular agonist-sensitive Ca2+ pool. However, releasing stored Ca2+ via alkalinization does not appear to trigger significant Ca2+ entry, perhaps because intracellular alkalinization inhibits either the Ca2+ entry pathway or the mechanism which couples the entry pathway to store depletion.

Acetic Acid↗
PubMed1997

Vietnamese and Arabic women's responses to the Diagnostic Interview Schedule (depression) and self-report questionnaires: cause for concern.

OBJECTIVE: The original study aimed to determine the best cut-off scores to screen for postnatal depression on translated versions of the Edinburgh Postnatal Depression Scale (EPDS) for Vietnamese and Arabic women. This research was conducted using the depression module of the Diagnostic interview Schedule (DIS) to determine caseness. This paper reports on the suitability of this diagnostic interview as a criterion measure of depression in these women with a non-English speaking background. METHOD: Vietnamese and Arabic women in south-west Sydney completed the EPDS and a General Health Questionnaire (GHQ-30) antenatally. At 6-8 weeks postpartum they completed an EPDS, the GHQ-30 and a Faces Scale, and were interviewed using the depression module of the DIS. Members of a small convenience sample of women were asked about the cultural appropriateness of each of the instruments. RESULTS: Vietnamese women admitted to few depressive symptoms on the DIS, whereas they appeared more open to reporting these on the EPDS and the GHQ-30. Arabic women responded more openly to the questionnaires and the interview, although they too were reluctant to report specific symptoms on the DIS. CONCLUSION: The usefulness of the DIS in determining rates of major depression in the Vietnamese and Arabic community in Australia is questionable. Further studies designed specifically to investigate this are needed.

Adult↗
PubMed1993

Personal and family distress in homeless adolescents.

Previous research has indicated that homeless children exhibit high rates of behavioral and emotional problems and come from families characterised by conflict and rejection. Further, some evidence exists to show that family variables may relate to adolescent distress differently for homeless males and females. In this study, 117 homeless adolescents were compared to a sample of non-homeless youths on the self reported incidence of personal and family problems. The homeless children reported the highest incidence of all behavioral and emotional problems, parental marital discord, overprotection, and the lowest levels of parental care and acceptance. Sex effects were not evident in reported levels of personal or family problems. However, substantially more variance in the adolescents level of behavioral and emotional disturbance was predictable from family measures for females than males. Overall, the results point to the importance of incorporating family distress models in the understanding and remediation of adolescent homelessness.

Adolescent↗
PubMed1990

Macular detachment following laser treatment for proliferative diabetic retinopathy.

Case records of patients who had macular detachment following argon laser photocoagulation for proliferative diabetic retinopathy were reviewed. Thirteen eyes of 11 patients out of a total of 480 patients treated had this complication, and in 12 eyes of 10 patients the short latency suggested a true precipitating effect. This represents 2.1% of patients receiving panretinal photocoagulation. Patients with detachment were younger and developed diabetes earlier than the controls (P less than 0.025), and the detached eyes had received more numerous laser burns on average per session than the controls (P less than 0.001). In 5 eyes the last photocoagulation dose exceeded 1000 burns delivered in the presence of traction membranes in an attempt to arrest continuing neovascular proliferation not responding to earlier more moderate treatment. Only 1 eye had received early, extensive and repeated photocoagulation. Vigorous treatment at an early stage of the proliferation may prevent this complication, although the advantages or disadvantages of fractionation of photocoagulation will only be shown by a prospective trial.

Adult↗
PubMed1990

Impact of human immunodeficiency virus on transmission and severity of tuberculosis.

It is now clear that tuberculosis is one of the major diseases associated with human immunodeficiency virus (HIV) infection and the acquired immune deficiency syndrome both in developing countries and in disadvantaged groups in the northern hemisphere. In the USA, and probably several other countries, the annual incidence of tuberculosis is rising as a result of the HIV epidemic. This is probably a result of an increase in both pulmonary and, especially, extrapulmonary tuberculosis, due to reactivation of latent infections, but a secondary increase in the infection rate is also possible. The hard-won gains in tuberculosis control of the last 30 years are thus in jeopardy. This article focuses on the effect HIV is likely to have on the known risk factors for infection with Mycobacterium tuberculosis and for reactivation. Whilst HIV-associated tuberculosis may be indistinguishable from HIV-negative disease, it is likely in other cases to present diagnostic difficulties, to respond poorly to treatment with more adverse effects, and to result in high early mortality, although this may not be due directly to tuberculosis. HIV-associated tuberculosis thus represents a major challenge to physicians, especially in developing countries, but like other forms of tuberculosis it is (i) treatable and (ii) preventable.

Acquired Immunodeficiency Syndrome↗
PubMed1989

The 'catch' mechanism in molluscan muscle: an electron microscopy study of freeze-substituted anterior byssus retractor muscle of Mytilus edulis.

A method for quick-freezing muscles while observing their mechanical properties until the moment of freezing is described. This method was used to freeze the anterior byssus retractor muscle (ABRM) of Mytilus edulis. Intact muscle in the presence of sucrose as a cryoprotectant was freeze-substituted in acetone, fixed and embedded for electron microscopy. ABRM was frozen in a number of mechanical states including 'catch', the state of high passive tension particularly associated with some molluscan muscles. Transverse sections were examined to determine the distribution of filaments in the muscle cells. In the relaxed muscle thick and thin filaments are fairly randomly distributed. Groups of thin filaments and of thick filaments are often seen, and there is no obvious association between the two types of filaments. In contrast, in rigor muscles, both glycerol-extracted and intact, most of the thin filaments were found to lie in rings or rosettes around the thick filaments. In some places bridges between thick and thin filaments could be distinguished. In actively contracting muscle (phasic contraction) the appearance is intermediate between that of the relaxed and rigor muscles. Many thick filaments are surrounded by rosettes of thin filaments but many of the thin filaments are grouped and have no connections with thick filaments. The 'catch' state, left after a period of tonic contraction, is similar in its distribution of thick and thin filaments to the active state, many of the thin filaments lying between the thick. Frequently thick and thin filaments seem to be closer together than in other states of the muscle where a pronounced exclusion zone is present around the thick filaments. There is no evidence for association between the thick filaments. The different distribution of thin filaments in the different states is consistent with the previously described X-ray diffraction data if it is assumed that most of the contribution to the equatorial reflection at 12 nm comes from the groups of thin filaments. Our data support a model for catch in which there is a change in the association between thick and thin filaments, rather than one in which thick filaments are clumped.

Actin Cytoskeleton↗
PubMed1989

Pupil size after extracapsular cataract extraction and posterior chamber lens implantation: a prospective randomized trial of epinephrine and acetylcholine.

The effects of using epinephrine in the irrigating fluid and intracameral acetylcholine were studied by measuring changes in pupil size in the 48 hours following extracapsular cataract extraction and intraocular lens implantation in 39 eyes. Epinephrine reduced peroperative pupil constriction, but its effect was insignificant thereafter. The pupil constriction following acetylcholine was maximal at 2 hours and was still significant at 4 hours, but pupils redilated by 6 hours. Neither drug had any effect after this time. The edge of most lens implants was visible at 6 hours, after which pupils steadily constricted.

Acetylcholine↗
PubMed1985

The structure of C-protein and X-protein molecules and a polymer of X-protein.

C-protein and X-protein are components of the thick filaments in vertebrate skeletal muscles and occupy similar locations in different fibre types. We find that the molecules are both rods about 30 to 40 A wide, but they differ significantly in their lengths, the X-protein molecule being about 350 A long and the C-protein molecule about 280 A. This suggests they are not isoforms. The short length of the C-protein molecule implies that it cannot act in the thick filament as a length-determining agent by a simple vernier mechanism. X-protein associates at low ionic strength (KCl concentration less than 0.07 M) but, unlike C-protein, forms long ordered polymers. These have been examined by electron microscopy to gain information on the molecular shape and on how the molecules interact. The polymers are helically twisted ribbons with a repeat distance along the axis of 660 A. The cross-section of the ribbon is approximately elliptical with major and minor axes of 405 A and 166 A, respectively. From an analysis of the micrographs by optical diffraction, we deduce that the molecules run across the face of the ribbon at an angle of about 15 degrees to the diameter and lie on a two-stranded helix. Models for the polymer are discussed in which the molecules are slightly bowed outwards and bind to each other only at their ends. We suggest that interactions similar to those in the polymer might occur in the thick filaments of muscle, and propose that at each axial position where X-protein attaches along the myosin filament, three X-protein molecules might form an approximately triangular ring around the filament backbone. The appearance of the X-protein polymers is similar to that of the twisted structures called paired helical filaments that make up the neurofibrillary tangles associated with dementia of the Alzheimer type.

Animals↗
PubMed1985

Tuberculin sensitivity in rural Gambian children.

A tuberculin survey was undertaken in 480 Gambian children under the age of 10 years, resident in a group of villages where BCG vaccination, shortly after birth, has been widely practised for about 5 years. Ten tuberculin units of purified protein derivative were given by needle and syringe; reactions of 3 mm or greater were considered positive. An overall tuberculin positivity rate of 59% was found which varied little with age, sex or village size. Among children who had probably not had BCG vaccination the positivity rate was about 20% with an annual increase of approximately 5%. Among children who had probably been vaccinated with BCG the positivity rate was between 60% and 80%. There was a fall in the prevalence of positivity of about 10-20% during the first year after vaccination. Thereafter, positivity rates were well maintained for at least another 5 years.

Age Factors↗
PubMed1985

Serum lactate dehydrogenase and creatine kinase during marathon training.

Serum total creatine kinase (CK) and the lactate dehydrogenase (LDH) isoenzymes were studied in 38 sedentary middle-aged men (aged 35-50 yrs) during a 30 week marathon training programme. Basal CK activity rose by 33% after 15 weeks but a significant rise (27%) in LDH activity took 30 weeks to occur. Post-exercise (maximum test on a bicycle ergometer) CK and LDH activities were higher than pre-exercise levels but the increment in enzyme activity following exercise did not change. LDH1 and LDH2 isoenzyme activity increased by 2.5% and 4% of total LDH respectively while LDH3 and LDH5 decreased by 3.9% and 2.4% respectively over 30 weeks. Post marathon total CK did not correlate with finishing time at 30 mins or 30 hrs post race. The range of CK MB isoenzyme activity at 30 mins post race was 1.8-9.8% of total CK with 11 subjects having a value above 6%. The training programme appears not to have affected muscle CK and LDH release during exercise but isoenzyme distribution changes reflect the adaptations known to occur in muscle during endurance training. Unfortunately only 16 subjects were available for all the investigations, and it is these upon whom most of the data were obtained.

Adult↗