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Biomedical subjects

S Demeter

Publications and source records attributed to S Demeter.

At least 19 recordsLinked to original sources
PubMed2006

The effect of socioeconomic status on bone density testing in a public health-care system.

INTRODUCTION AND HYPOTHESIS: An inverse relationship exists between socio-economic status (SES) and osteoporotic fractures. In publicly funded health-care systems there should be no barriers to accessing bone mineral density (BMD) testing, especially for those at increased fracture risk. Our hypothesis was that there would be a positive association between SES and BMD utilization (i.e. higher utilization rates in higher income women), resulting in disparities that disadvantage lower SES or lower income women. METHODS: A population-based BMD database from the Manitoba Bone Density Program was utilized to assess the association between SES (defined using income quintiles) and BMD utilization rates in women aged 50 years and older (n=107,944) for the 2001-2002 fiscal year. Analyses were stratified by age (50-64 years old and 65 years or older) and by a morbidity index obtained from the Johns Hopkins University Adjusted Clinical Group Case-Mix Adjustment System. RESULTS: Regression models demonstrated significantly higher BMD utilization rates among high SES women in all age and morbidity strata. Rate ratios varied from 1.76 (95% CI: 1.52-2.04) in 50- to 64-year-old women to 2.36 (95% CI: 1.60-3.49) in low morbidity women aged 65 or older. CONCLUSION: Within the context of a publicly funded health-care system significant inverse associations are demonstrated between SES and BMD utilization rates. Further research is needed to better understand the nature of these associations and how they may contribute to health outcomes.

Adult↗
PubMed2001

Non-penetrating glaucoma surgery using AquaFlow(TM)collagen implants.

AquaFlow TM is an absorbable collagen implant for use in non-penetrating surgery for primary open angle glaucoma. Its purpose is to facilitate drainage of fluid from the eye, thereby reducing intraocular pressure. AquaFlow TM is approved for use in Canada in medically refractory cases of primary open angle glaucoma. Non-penetrating glaucoma surgery with the AquaFlow TM implant appears to be a relatively safe procedure. However, there is a steep learning curve for the surgeon and it is initially associated with a high rate of conversion to conventional surgery during the operation. Limited evidence from small non-randomized trials suggests that the AquaFlow TM implant may offer benefits over conventional surgical approaches in terms of reduced complication rates, reduced medication use, an earlier return of improved vision and sustained control of intraocular pressure. However, the efficacy and cost-effectiveness of this approach have not been established. January, 2001 for use in patients with uncontrolled

Canada↗
PubMed2000

Short- and long-term redox regulation of photosynthetic light energy distribution and photosystem stoichiometry by acetate metabolism in the green alga, Chlamydobotrys stellata.

The effect of acetate metabolism on the light energy distribution between the two photosystems, on the PS II/PS I stoichiometry and on the expression of psbA and psbB and psaA genes was investigated in the green alga, Chlamydobotrys stellata during autotrophic (CO(2)), mixotrophic (CO(2) plus acetate) and photoheterotrophic (only acetate) cultivation. It was observed that acetate assimilation in the glyoxylate cycle resulted in a large drop in the ATP content and a concomitant increase in the NADPH content of the cells. The combined effect of high NADPH concentration and linear electron transport brought about an over-reduction of the inter-photosystem electron transport components. The reduced state of the inter-photosystem components initiated a state 1/state 2 transition of LHC II and a decrease in the PS II/PS I ratio. The PS II/ PS I ratio was reduced because the synthesis of PS II reaction centers was repressed and that of the PS I reaction centers was slightly enhanced by acetate cultivation. The amount of PsbA and PsbB proteins of PS II and the abundance of psbA mRNA decreased. The abundance of PS I PsaA protein and psaAmRNA were only slightly increased. All of the acetate-induced effects were reversible when the cells were transferred back to an acetate-free medium. Our observations demonstrate that the expression of the PS II psbA and psbB and PS I psaA genes is regulated by the redox state of the inter-photosystem components at the transcriptional level. Experiments carried out in the presence of DBMIB which facilitates the reduction of plastoquinone pool indicate that the expression of genes encoding the components of PS II and PS I are controlled by the redox state of a component (cytochrome b/f complex) located behind the plastoquinone pool.

Journal Article↗
PubMed1995

Noncardiac pulmonary edema, newer environmental aspects. An update.

Accidental spread of potentially toxic gases, fumes, and particulate chemicals has been reported recently in various cities throughout the country and appears to be on the increase throughout the world in the past few years. Moreover, cerebral trauma, septic shock (ARDS), and environmental pulmonary edema from drug intoxication have been commonly encountered. Newer modalities of treatment include selective [corrected] fiber optic bronchoscopy, constant positive airway pressure mask, administration of surfactant, pentoxifylline, and use of newer experimental agents such as nitrous oxide, antitumor necrosis factor (ATNF), and extracorporeal carbon dioxide with low-frequency positive pressure (ECCO2R-LFPPV). The future holds promise for probable reductions in both morbidity and mortality rates of this ubiquitous occupational and environmental health problem, which is of global importance.

Accidents, Occupational↗
PubMed1993

Participation of the g = 1.9 and g = 1.82 EPR forms of the semiquinone-iron complex, QA-.Fe2+ of photosystem II in the generation of the Q and C thermoluminescence bands, respectively.

Following illumination at 200 K, the charge recombination reactions and the origin of the thermoluminescence (TL) bands appearing at about 0 degree C (Q band) and +50 degrees C (C band) in the glow curve were investigated by comparative TL and EPR measurements in DCMU-treated photosystem II particles. Decay half-time measurements carried out at -25 degrees C and +25 degrees C, respectively, suggest that the S2 state (multi-line signal) undergoes charge recombination with the g = 1.9 form of the semiquinone-iron complex, QA-.Fe2+, resulting in the appearance of the Q band, and that the g = 1.82 form of QA-.Fe2+ back-reacts with the oxidized tyrosine, YD+ (Signal IIs), accounting for the generation of the C band.

Benzoquinones↗
PubMed1992

Thermoluminescence evidence for light-induced oxidation of tyrosine and histidine residues in manganese-depleted photosystem II particles.

In the thermoluminescence (TL) glow curve of photosystem II, particles depleted of manganese, a tyrosine modifier, 7-chloro-4-nitrobenz-2-oxa-1,3-diazole (NBD) abolishes the TL band appearing around -55 degrees C (TL-55). Addition of a histidine modifier, diethylpyrocarbonate results in the disappearance of the band peaking around -30 degrees C (TL-30). NBD treatment also abolishes the EPR signal IIfast of oxidized tyrosine donor, Yz, and inhibits the electron transport from diphenylcarbazide to 2,6-dichlorophenol-indophenol. It is concluded that the TL-55 and TL-30 bands can be assigned to oxidized tyrosine (Yz+) and histidine (His+) residues, respectively, which participate in electron transfer from manganese to the reaction center of chlorophyll, P680+.

4-Chloro-7-nitrobenzofurazan↗
PubMed1992

Hydrogen Photoevolution Indicates an Increase in the Antenna Size of Photosystem I in Chlamydobotrys stellata during Transition from Autotrophic to Photoheterotrophic Nutrition.

The changes in the light-harvesting antenna size of photosystem I were investigated in the green alga Chlamydobotrys stellata during transition from autotrophic to photoheterotrophic nutrition by measuring the light-saturation behavior of hydrogen evolution following single turnover flashes. It was found that during autotrophic-to-photoheterotrophic transition the antenna size of photosystem I increased from 180 to 250 chlorophyll. The chlorophyll (a + b)/P700 ratio decreased from 800 to 550. The electron transport of photosystem I measured from reduced 2,6-dichloro-phenolindophenol to methylviologen was accelerated 1.4 times. In the 77K fluorescence spectra, the photosystem II fluorescence yield was considerably lowered relative to the photosystem I fluorescence yield. It is suggested that the increased light-harvesting capacity and redistribution of absorbed excitation energy in favor of photosystem I is a response of photoheterotrophic algae to meet the ATP demand for acetate metabolism by efficient photosystem I cyclic electron transport when the noncyclic photophosphorylation is inhibited by CO(2) deficiency.

Journal Article↗
PubMed1991

Bi-versus monohemispheric performance in split-brain and partially split-brain macaques.

Experiments comparing binocular with monocular abilities of monkeys working on visual mnemonic tasks were performed. First, it was shown that even in split-brain monkeys performance was more accurate when both hemispheres were utilized than when the task was performed with only the single (better) hemisphere. Some form of noncommissural integration is thus possible. However, when the forebrain commissures are present, as in four other animals (with only optic chiasm transected) it was shown that integration occurs via callosal mechanisms as well. This was demonstrated by the fact that here, too, binocular performance was normally more accurate than monocular performance, but when different images to be remembered were presented concurrently to the two eyes, the binocular advantage was lost. Finally, in three monkeys with only the anterior commissure allowing interhemispheric communication the superiority of binocular assessment remained even when the two hemispheres simultaneously received such differing images.

Animals↗
PubMed1990

Fields of origin and pathways of the interhemispheric commissures in the temporal lobe of macaques.

The interhemispheric connections of the cortical areas of the temporal lobe and some neighboring regions were investigated in monkeys (Macaca mulatta and Macaca fascicularis) by anterograde autoradiographic tracing, following injection of radioactively labeled amino acids. The results revealed that the interhemispheric projections of the temporal lobe course through three interhemispheric commissures on their way to the opposite hemisphere. The anterior commissure receives fibers from virtually the entire temporal lobe, including the temporal pole, superior and inferior temporal gyri, and parahippocampal gyrus. Moreover, area 13 of the orbitofrontal cortex, the frontal and temporal subdivisions of the prepiriform cortex, and the cortical and deep nuclei of the amygdala also contribute fibers to the anterior commissure. The heaviest projections arise in the rostral third of the temporal isocortex. These projections become progressively lighter from more caudal regions. By contrast, the corpus callosum receives fibers from the caudal two-thirds of the temporal lobe, including the temporal pole, superior and inferior temporal gyri, and parahippocampal gyrus. The heaviest projections arise in the caudal third of the temporal lobe and cross primarily in the caudal third of the corpus callosum, including the splenium. Progressively lighter projections arise more rostrally. Fibers from proisocortical and isocortical areas of the posterior parahippocampal gyrus cross in the ventralmost part of the splenium (inferior forceps), whereas cortical areas lateral to the occipitotemporal sulcus give rise to fibers that cross in the caudal part of the body of the corpus callosum and dorsal splenium. The dorsal hippocampal commissure receives fibers exclusively from the parahippocampal gyrus. The fibers of the corpus callosum, hippocampal commissure, and, to a lesser extent, the anterior commissure are intimately associated with the ventricular system as they course through the white matter of the temporal lobe. The fields of origin of the anterior commissure and corpus callosum overlap extensively over the caudal two-thirds of the temporal lobe. The posterior parahippocampal gyrus is unique in that it gives rise to fibers that cross in all three commissures.

Amygdala↗
PubMed1990

AS-1 cyanophage infection inhibits the photosynthetic electron flow of photosystem II in Synechococcus sp. PCC 6301, a cyanobacterium.

In Synechococcus sp. cells AS-1 cyanophage infection gradually inhibits the photosystem II mediated photosynthetic electron flow whereas the activity of photosystem I is apparently unaffected by the cyanophage infection. Transient fluorescence induction and flash-induced delayed luminescence decay studies revealed that the inhibition may occur at the level of the secondary acceptor, QB of photosystem II. In addition, the breakdown of D1-protein is inhibited, comparable to DCMU-induced protection of D1-protein turnover, in AS-1-infected cells.

Chlorophyll↗
PubMed1990

Multiplane gallium tomography in assessment of occupational chest diseases.

Gallium-67 scintigraphy is helpful in the evaluation of inflammatory, respiratory diseases. Single-photon emission computed tomography (SPECT) provides three-dimensional tomographic reconstruction of radioisotope distribution in the body. The addition of SPECT to gallium-67 scanning in 27 patients demonstrated an improvement in the sensitivity for detecting the presence and extent of interstitial occupational lung disease. This technique may provide earlier detection of parenchymal lung changes than can the chest x-ray and planar scanning in some patients with asbestosis. Findings in six patients with asbestosis are reported.

Adult↗
PubMed1989

Copper Toxicity Affects Photosystem II Electron Transport at the Secondary Quinone Acceptor, Q(B).

The nature of Cu(2+) inhibition of photosystem II (PSII) photochemistry in pea (Pisum sativum L.) thylakoids was investigated monitoring Hill activity and light emission properties of photosystem II. In Cu(2+)-inhibited thylakoids, diphenyl carbazide addition does not relieve the loss of Hill activity. The maximum yield of fluorescence induction restored by hydroxylamine in Tris-inactivated thylakoids is markedly reduced by Cu(2+). This suggests that Cu(2+) does not act on the donor side of PSII but on the reaction center of PSII or on components beyond. Thermoluminescence and delayed luminescence studies show that charge recombination between the positively charged intermediate in water oxidation cycle (S(2)) and negatively charged primary quinone acceptor of pSII (Q(A) (-)) is largely unaffected by Cu(2+). The S(2)Q(B) (-) charge recombination, however, is drastically inhibited which parallels the loss of Hill activity. This indicates that Cu(2+) inhibits photosystem II photochemistry primarily affecting the function of the secondary quinone electron acceptor, Q(B). We suggest that Cu(2+) does not block electron flow between the primary and secondary quinone acceptor but modifies the Q(B) site in such a way that it becomes unsuitable for further photosystem II photochemistry.

Journal Article↗
PubMed1989

Crohn's disease (regional enteritis) in association with Hodgkin's disease.

It has long been known that Crohn's disease may occur in association with certain forms of malignancy, specifically adenocarcinoma and lymphoma of the bowel and carcinoma of the vulva and perianal area. Here, the authors report the rare occurrence of extraintestinal Hodgkin's disease in a patient with documented regional enteritis of five years' duration. They propose explanations for this unusual combination of disease, reported in the literature only once previously, and review the pathophysiology of lymphoma and regional enteritis.

Adult↗