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PubMed2001

An efficient photoelectric X-ray polarimeter for the study of black holes and neutron stars.

The study of astronomical objects using electromagnetic radiation involves four basic observational approaches: imaging, spectroscopy, photometry (accurate counting of the photons received) and polarimetry (measurement of the polarizations of the observed photons). In contrast to observations at other wavelengths, a lack of sensitivity has prevented X-ray astronomy from making use of polarimetry. Yet such a technique could provide a direct picture of the state of matter in extreme magnetic and gravitational fields, and has the potential to resolve the internal structures of compact sources that would otherwise remain inaccessible, even to X-ray interferometry. In binary pulsars, for example, we could directly 'see' the rotation of the magnetic field and determine if the emission is in the form of a 'fan' or a 'pencil' beam. Also, observation of the characteristic twisting of the polarization angle in other compact sources would reveal the presence of a black hole. Here we report the development of an instrument that makes X-ray polarimetry possible. The factor of 100 improvement in sensitivity that we have achieved will allow direct exploration of the most dramatic objects of the X-ray sky.

Journal Article↗

PubMed1991

Distribution and photodynamic effect of disulphonated aluminium phthalocyanine in the pancreas and adjacent tissues in the Syrian golden hamster.

Necrosis of small volumes of tumour tissue with photodynamic therapy (PDT) can be achieved relatively easily. For this to be clinically relevant, it is essential to know what the same treatment parameters do to adjacent normal tissues into which the tumour has spread. For pancreatic cancers, local spread to vital structures is common. We have studied chemical extraction, microscopic fluorescence kinetics and photodynamic effects of disulphonated aluminum phthalocyanine (AlS2Pc) in normal pancreas and adjacent tissues in hamsters. Chemical extraction exhibited a peak duodenal concentration of AlS2Pc 48 h after sensitisation, with levels much higher than in stomach and pancreas. With microscopic fluorescence photometry highest levels were seen in duodenal submucosa and bile duct walls 48 h after photosensitisation. Pancreatic ducts, duodenal mucosa and gastric mucosa and submucosa exhibited intermediate fluorescence with relatively weak fluorescence in pancreatic acinar tissue and the muscle layer of the stomach. As expected, on the basis of fluorescence intensity and chemical extraction studies, the duodenal and bile duct wall were the most vulnerable tissues to photodynamic therapy. When the dose of 5 mumol kg-1 of sensitiser was used, duodenal perforations, gastric ulcers and transudation of bile from the bile duct occurred. However, the lesions in the stomach and bile duct healed without perforation or obstruction, so only the duodenum was at risk of serious, irreversible damage. Using a lower dose of photosensitiser markedly reduced damage.

Animals↗

PubMed1988

Kinetics, dynamics, and bioavailability of bumetanide in healthy subjects and patients with congestive heart failure.

Four healthy subjects and six patients with congestive heart failure (CHF) were given 3 mg oral and intravenous doses of bumetanide in a random crossover fashion. Bumetanide was analyzed by HPLC, and sodium and potassium was analyzed by flame photometry. Aside from a modest reduction in renal clearance, the kinetics of bumetanide in CHF were similar to those in healthy subjects. The extent of bioavailability was 81%, with a variability of 20% to 25% about the mean for both groups. The cumulative dynamic responses to bumetanide, whether administered orally or intravenously, were essentially the same in each group. Pharmacodynamic modeling showed that there were no significant differences between healthy subjects and patients with CHF in either ER50 (bumetanide urinary excretion rate producing 50% of maximum drug effect) or S (slope), although the baseline effect was 15 times lower in CHF. The maximum effect attributable to bumetanide was twofold higher in healthy subjects and there was a significant correlation between this parameter and creatinine clearance (r = 0.964; p less than 0.001). Overall, these results indicate that a predictable transition from 3 mg intravenous to oral doses of bumetanide is possible in CHF.

Administration, Oral↗

PubMed1988

Ischemic brain edema and the osmotic gradient between blood and brain.

The relationship of the osmotic pressure gradient between blood and brain, and the development of ischemic brain edema was studied. Focal cerebral ischemia was produced by left middle cerebral artery occlusion in rats. Brain osmolality was determined with a vapor pressure osmometer, brain water content by wet-dry weight, and tissue sodium and potassium contents by flame photometry. Permeability of the BBB was tested by Evans blue. Measurements were made from the ischemic cortex within 14 days of occlusion. Brain osmolality increased from 311 +/- 2 to 329 +/- 2 mOsm/kg by 6 h after occlusion. Serum osmolality did not change significantly. The osmotic gradient between blood and brain peaked at approximately 26 mOsm/kg. Brain osmolality then decreased to 310 +/- 2 mOsm/kg by 12 h after occlusion and remained at about that same level. Water content increased progressively within 1 day of occlusion, then gradually decreased by 14 days. Brain tissue sodium plus potassium content did not increase within 6 h of occlusion, and Evans blue extravasation was not seen within that time. These findings indicate that an osmotic pressure gradient contributes to the formation of edema only during the early stage of cerebral ischemia. Furthermore, the increase in brain osmolality is not related to tissue electrolyte change or BBB disruption to protein.

Animals↗

PubMed1996

Characterization of sodium-calcium exchange in rabbit renal arterioles.

Experiments were performed to test the hypothesis that renal arterioles exhibit Na-Ca exchange capability and that this process is regulated by protein kinase C (PKC). Glomeruli with attached arterioles were dissected from rabbit kidney and loaded with fura-2 for measurement of intracellular calcium concentration ([Ca2+]i) using microscope-based photometry. In tissue bathed in Ringer's solution containing 150 mM Na+ and 1.5 mM Ca2+, afferent and efferent arteriolar [Ca2+]i averaged 136 +/- 6 and 154 +/- 7 nM, respectively. Removal of extracellular Na+ increased afferent arteriolar [Ca2+]i by 70 +/- 7 mM, while efferent arteriolar [Ca2+]i only increased by 39 +/- 5 nM (P < 0.01 vs. afferent arteriole). These responses were inhibited by 6 nM Ni2+ and required extracellular Ca2+, but were unaffected by 10 microM diltiazem. After incubation in 500 microM ouabain, 5 microM monensin, and 5 microM nigericin, [Ca2+]i responses to removal of extracellular Na+ were exaggerated significantly, averaging 174 +/- 50 nM in afferent arterioles and 222 +/- 82 nM in efferent arterioles (NS vs. afferent arterioles). Moreover, responses to removal of extracellular Na+ were enhanced by 100 nM phorbol 12-myristate 13-acetate, an affect which was blocked by PKC inhibition (25 nM K252b). These data indicate that both afferent and efferent arterioles express the Na-Ca exchanger, and that PKC activity impacts on exchange capacity in these vessels.

Animals↗

PubMed1996

Altered sodium-calcium exchange in afferent arterioles of the spontaneously hypertensive rat.

Studies were performed to determine if there is a derangement in Na-Ca exchange activity in afferent (AA) and efferent (EA) arterioles from 3- and 9-week-old spontaneously hypertensive (SHR) and Wistar-Kyoto (WKY) rats. Cytosolic calcium concentration ([Ca2+]i) was assessed using microscope-based photometry in fura-2 loaded arterioles bathed in a Ringer's solution. Baseline [Ca2+]i was similar in the AA of 3- and 9-week-old WKY and SHR. In AA from 3-week-old rats, [Ca2+]i increased by 89 +/- 15 nM in WKY and by 73 +/- 13 nM in SHR during decreases in bath sodium concentration ([Na+]e) from 150 to 2 mM (Na+ replaced with n-methyl-D-glucamine). In 9-week-old hypertensive SHR (SBP = 150 mm Hg), increases in [Ca2+]i were attenuated (24 +/- 3 nM) relative to 3-week-old WKY and SHR, and 9-week-old WKY (90 +/- 9 nM; P < 0.05). Likewise, the rate of removal of Ca2+ in the continued presence of 2 mM Nae (Ca2+ sequestration and/or extrusion) was markedly reduced in AA of 9-week-old SHR (-0.15 +/- 0.03 nM/second) versus 3-week-old SHR (-0.72 +/- 0.12 nM/second) and 3- and 9-week-old WKY (-0.49 +/- 0.10 and -0.67 +/- 0.14 nM/second). In other experiments, AAs were preincubated in 1 mM ouabain to increase intracellular [Na+]. This maneuver augmented the increase in [Ca2+]i obtained with removal of Na+e; however, the responses obtained in 9-week-old SHR arterioles were still attenuated compared to those obtained in arterioles for 3- and 9-week-old WKY and 3-week-old SHR. These results suggest that exchanger number and/or sensitivity to the transmembrane Na gradient was reduced in the SHR AA. In EA, baseline [Ca2+]i was similar in 3- and 9-week-old WKY and SHR. In contrast to AA, the magnitude of Na-dependent and Na-independent changes in [Ca2+]i was not different in the EA of 3- and 9-week-old WKY and SHR. These results indicate that regulation of Na-Ca exchange activity may differ between AA and EA segments. Furthermore, diminished Na-Ca exchange and Na-independent Ca2+ sequestering/extrusion mechanisms could contribute to altered AA [Ca2+]i in the SHR.

Animals↗

PubMed2004

Asteroseismology: oscillations on the star Procyon.

Stars are spheres of hot gas whose interiors transmit acoustic waves very efficiently. Geologists learn about the interior structure of Earth by monitoring how seismic waves propagate through it and, in a similar way, the interior of a star can be probed using the periodic motions on the surface that arise from such waves. Matthews et al. claim that the star Procyon does not have acoustic surface oscillations of the strength predicted. However, we show here, using ground-based spectroscopy, that Procyon is oscillating, albeit with an amplitude that is only slightly greater than the noise level observed by Matthews et al. using spaced-based photometry.

Comment↗

PubMed2002

A sensitive and specific enzyme-based assay detecting HIV-1 virion fusion in primary T lymphocytes.

As an early event in the viral life cycle, the entry of enveloped viruses into target cells has received considerable attention. Viral fusion to cellular targets has been studied principally with fusion assays in which cells engineered to express the viral envelope are cultured with the target cells. These assays yield valuable information but do not fully recapitulate all of the variables governing the fusion of actual virions to their cellular targets. The virion membrane and the plasma membrane, for example, differ strikingly in their lipid and protein compositions. Two virion-based fusion assays have been described. One is based on the redistribution of a self-quenching fluorophore, whereas the second depends on photosensitized activation of a hydrophobic probe by a fluorescent lipid loaded into the target membrane. These assays are complex and have not been adapted to study fusion in complex cell populations. We have developed a simple, rapid assay allowing the detection of HIV-1 virion fusion to biologically relevant target cells, including primary CD4(+) T lymphocytes. It is based on the incorporation of beta-lactamase-Vpr chimeric proteins (BlaM-Vpr) into HIV-1 virions and their subsequent delivery into the cytoplasm of target cells as a result of virion fusion. This transfer is then detected by enzymatic cleavage of the CCF2 dye, a fluorescent substrate of beta-lactamase (BlaM), loaded in the target cells. BlaM cleaves the beta-lactam ring in CCF2, changing its fluorescence emission spectrum from green (520 nm) to blue (447 nm) and thereby allowing fusion to be detected by fluorescence microscopy, flow cytometry, or UV photometry.

Cell Fusion↗

PubMed2006

Severe uveitis in an HLA-B27-positive patient with ankylosing spondylitis.

BACKGROUND: A 36-year-old male presented with bilateral, anterior, chronic uveitis, with cystoid macular edema. Decimal visual acuity was 0.25 in the right eye and 0.20 in the left eye. Ankylosing spondylitis had been diagnosed 13 years previously, with peripheral and axial involvement. He had no history of extra-articular manifestations of ankylosing spondylitis before this uveitis attack. Treatment with the anti-tumor necrosis factor agent etanercept was initiated 5 months before the attack of uveitis. INVESTIGATIONS: Slit-lamp biomicroscopy, laser-flare photometry, optical coherence tomography, chest radiography, angiotensin-converting-enzyme test, mycobacterial culture from gastric lavage, serology tests for syphilis, brucellosis, toxoplasmosis, toxocarosis, antinuclear antibodies, rheumatoid factor, antineutrophil cytoplasmic antibodies, antimyeloperoxydase antibodies and antiproteinase 3 antibodies. DIAGNOSIS: Atypically severe HLA-B27-positive uveitis, in a patient with ankylosing spondylitis treated with etanercept. MANAGEMENT: Intensive topical corticosteroid and cycloplegic treatment, subtenon triamcinolone acetonide injection, switch in treatment from etanercept to infliximab followed by discontinuation of tumor necrosis factor inhibitors, intravenous pulses of methylprednisolone followed by oral corticosteroids, and intravenous cyclophosphamide.

Adult↗

PubMed2006

Beta3-adrenoceptor agonist stimulation of the Na+, K+ -pump in rat skeletal muscle is mediated by beta2- rather than beta3-adrenoceptors.

BACKGROUND AND PURPOSE: In cardiac muscle, BRL 37344, a selective beta3-adrenoceptor agonist, activates the Na+, K+ -pump via NO signalling. This study investigated whether BRL 37344 also activates the Na+, K+ -pump via beta3-adrenoceptors in skeletal muscle. EXPERIMENTAL APPROACH: Isolated rat soleus muscles were incubated between 1 and 60 min in buffer. Intracellular Na+, K+ content and Na+, K+ -pump activity were measured using flame photometry and ouabain-suppressible 86Rb+ uptake, respectively. Additional muscles were mounted on force transducers and stimulated (60 Hz for 2 s) every 10 min. KEY RESULTS: BRL 37344 (10(-8) -10(-5) M) induced a concentration- and time-dependent reduction in intracellular Na+, and increased ouabain-suppressible 86Rb+ uptake by up to 112%. BRL 37344-induced reductions in intracellular Na+ were blocked by the beta1/beta2-adrenoceptor antagonist, nadolol (10(-7) M), and the beta2-adrenoceptor antagonist, ICI 118,551 (10(-7) -10(-5) M), but not by beta3- or beta1-adrenoceptor antagonists, SR 59230A (10(-7) M) and CGP 20712A (10(-7) -10(-5) M), respectively. Another beta3-adrenoceptor agonist, CL 316,243, did not alter intracellular Na+. BRL 37344-induced reductions in intracellular Na+ were not blocked by L-NAME, an NOS inhibitor, or ODQ, a guanylyl cyclase inhibitor. The NO donors, SNP and SNAP, did not alter intracellular Na+. BRL 37344 rapidly recovered force in muscles depressed by high [K+]o, an effect that was blocked by nadolol, but not L-NAME. CONCLUSIONS AND IMPLICATIONS: In rat soleus muscle, the beta3-adrenoceptor agonist BRL 37344 stimulated the Na+, K+ -pump via beta2-adrenoceptors. A more selective beta3-adrenoceptor agonist did not affect Na+, K+ homeostasis in skeletal muscle. NO did not seem to mediate Na+, K+ -pump stimulation in skeletal muscle.

Adrenergic beta-Agonists↗

PubMed2006

Sugar-, acid- and phenol contents in apple cultivars from organic and integrated fruit cultivation.

OBJECTIVE: This study was carried out to obtain data about the sugar-, acid- and phenol content of apple cultivars from organic and integrated fruit cultivation, with reference to their role in human health and especially for diet recommendations. SETTING: Styria (Austria) and Slovenia. INTERVENTIONS: HPLC, Spectral Photometry, organoleptic and olfactory tests. RESULTS: The total sugar content of most cultivars from integrated cultivation ranged between 115 and 160 g/kg. Some cultivars from organic growing reached higher values. The acid content of both cultivar types was similar. The phenol content in organically grown cultivars was much higher than that of the ones from integrated cultivation. CONCLUSION: Knowledge of the sugar content is very important for diabetic patients, owing to the assumption of general diet recommendations that 100 g fruit contain 12 g carbohydrates. This applies to most well-known cultivars like Golden Delicious or Gala, but not to most of the regional cultivars. For diabetics, it is necessary to know the carbohydrate content of food precisely, in order to adapt the amount of insulin to the ingestion. So, it is helpful to know the sugar content of each regional cultivar. Moreover, very high levels of phenolic compound in organically grown cultivars, and with it its importance for human health leads to the recommendation to eat regional fruits from organic fruit growing instead of those grown under integrated cultivation.

Acids↗

PubMed2005

A 6-month assessment of bimatoprost 0.03% vs timolol maleate 0.5%: hypotensive efficacy, macular thickness and flare in ocular-hypertensive and glaucoma patients.

AIM: To compare 6 months of treatment with bimatoprost and timolol in terms of their hypotensive efficacy and secondary effects, including changes in macular thickness and the inflammatory reaction induced in the anterior chamber. METHODS: A prospective, randomized, parallel-group trial performed on 30 eyes of 30 patients per group. The main outcome measure was the difference between the IOP value taken between the baseline visit and the 6-month-visit. Macular thickness determined through optical coherence tomography and anterior chamber inflammation estimated using the laser flare meter was also evaluated. Adverse events were recorded during the study period. RESULTS: Bimatoprost treatment gave rise to a significantly lower mean IOP than timolol in all follow-up visits as from the first month (P<0.05). Bimatoprost achieved high percentage IOP reductions from baseline in a significantly higher proportion of patients (P<0.05). Macular thickness and anterior chamber flare failed to vary significantly both between the two groups and within each group during the 6-month evaluation (P>0.05). CONCLUSIONS: Bimatoprost 0.03% once daily showed a greater efficacy then timolol 0.05% twice daily in patients with elevated IOP. No significant differences were detected in macular thickness or anterior uveitis using optical coherence tomography and laser flare photometry.

Adult↗

PubMed1998

Sodium-lithium countertransport activity in normotensive offspring of hypertensive black Africans.

OBJECTIVE: To assess sodium-lithium countertransport (SLC) activity and erythrocyte sodium (ENa) levels in black (Nigerian) hypertensive (HT) patients, normotensive (NT) offspring of hypertensive parents and normotensive offspring of normotensive parents, and to determine if increased SLC activity is related to a familial predisposition to hypertension in black subjects as in Caucasians. METHOD: The study was done using 60 Nigerian subjects of Edo ethnic origin in three groups of 20 each: (a) untreated new HT patients at the University Teaching Hospital, Benin City; (b) NT children of hypertensive parents (NTHT) traced home and matched for age, sex and body mass index (BMI) with (c) NT children of NT parents (NTNT). SLC activity was measured using a modified method of Canessa et al 1980 and ENa assessed by flame photometry. RESULTS: SLC was markedly higher in both HT patients and NTHT subjects than the NTNT subjects. The values were 0.351+/-0.011 vs 0.199+/-0.014 mmol Li/rbc (P < 0.0001) and 0.347+/-0.020 vs 0.199+/-0.014 mmol Li/rbc/hr (P < 0.0001), respectively. The values were not different between the HT and the NTHT group (P > 0.05). ENa was higher in the HT group than both NT groups which were similar. Values were 10.55+/-0.46 (HT) vs 7.78+/-0.62 (NTHT) (P < 0.0001) and 10.55+/-0.46 (HT) vs 8.62+/-0.47 mmol/L (P < 0.0001). There were no correlations between either SLC activity or ENa and any of the other measured variables such as age or BMT. CONCLUSIONS: SLC activity was elevated in normotensive children of hypertensive subjects to a similar degree as hypertensive patients and in a pattern reminiscent of that seen in Caucasians. SLC activity may thus be associated with a familial predisposition to hypertension in black subjects as in their Caucasian counterparts.

Adult↗

PubMed1999

Cell cycle arrest and morphological alterations following microinjection of NIH3T3 cells with Pur alpha.

Levels of Pur alpha, a protein implicated in control of both DNA replication and gene transcription, fluctuate during the cell cycle, being lowest in early S phase and highest just after mitosis. Here we have employed a new video time-lapse technique enabling us to determine the cell cycle position of each cell in an asynchronous culture at a given time and to ask whether introduction of Pur alpha protein at specific times can affect cell cycle progression. Approximately 80% of all NIH3T3 cells injected with Pur alpha were inhibited from passing through mitosis. Cells injected with Pur alpha during S or G2 phases were efficiently blocked with a 4N (G2 phase) DNA level, as determined by quantitative DNA photometry of individual cells. Of the cells injected with Pur alpha during G1 phase, 40% experienced a rapid cell death characterized by extreme cellular fragmentation. Of those G1 injected cells which remained viable, approximately equal numbers were arrested with either 2N or 4N DNA levels. Cells arrested by Pur alpha in G2 phase grew to cover a large surface area. These results link fluctuations in Pur alpha levels to aspects of cell cycle control.

3T3 Cells↗

PubMed2004

On-site simultaneous determination of anions and cations in drainage water using a flow injection-capillary electrophoresis system with contactless conductivity detection.

Drainage water diverted from a farm pasture, which was heavily loaded with manure, was monitored during a rain event. Concurrent anion and cation determinations at intervals of 10 min could be achieved with a new capillary electrophoresis system employing dual injection at opposite ends of the separation capillary. The flow injection approach enabled automation of the sampling process. Interruption of the separation voltage was not necessary. Contactless conductivity detection with an electrolyte solution optimized for the purpose allowed the facile simultaneous detection of the inorganic ions Cl(-), NO(3)(-), SO(4)(2-), HPO(4)(2-), NO(2)(-), NH(4)(+), K(+), Ca(2+), Na(+) and Mg(2+) and the acquisition of temporal concentration profiles of these species. The detection limits achieved were between 20 and 200 [micro sign]g l(-1) for all ions and the repeatability of peak areas and peak heights was better than 1%. The quantitative results were verified by analysing individual samples later in the laboratory with photometry and ion chromatography and the average deviations were found to be between 4 and 12%. This contribution presents a further step in the development of capillary electrophoresis towards a fully automated, low maintenance field method.

Anions↗

PubMed1976

State and accessibility of zinic in yeast alcohol dehydrogenase.

1. Yeast alcohol dehydrogenase (EC 1.1.1.1) is inhibited in the presence of 1,10-phenanthroline. 2. A conformational change in the enzyme's structure is induced by 1,10-phenanthroline, and is abolished in the presence of NADH. 1,10-Phenanthroline binds to the enzyme competitively with respect to NADH, with a stoicheiometry of 2 mol of 1,10-phenanthroline/144000g of enzyme. 3. 1,10-Phenanthroline induces a time-dependent dissociation of Zn2+ from the enzyme, which is in correlation with its inhibitions. 4. Spectrophotometric measurement indicates that the dissociation of half (2 zinc atoms/tetramer) of the total zinc content of the enzyme correlates with the full inhibition of its activity. Measurement of the tightly bound Zn2+ by atomic absorption photometry confirms this. 5. A proposition is advanced that the tetrameric molecule of yeast alcohol dehydrogenase possesses an inherent asymmetry, with four monomeric subunits being arranged in two mutually symmetrical pairs.

Alcohol Oxidoreductases↗

PubMed1977

Alloxan cytotoxicity in vitro. Microscope photometric analyses of Trypan Blue uptake by pancreatic islet cells in suspension.

Suspensions of islet cells were prepared by shaking pancreatic islets from non-inbred ob/ob mice in a Ca2+-free buffer. The cells were incubated with or without 20 mM-alloxan, and subsequently with Trypan Blue. The uptake of Trypan Blue by cell nuclei was analysed by microscope photometry and by counting the frequency of cells appearing stained on visual inspection. Cells classified as stained or unstained by inspection showed no overlap in nuclear absorbance. Suspensions not exposed to alloxan contained 70-80% of unstained cells. Alloxan markedly decreased the frequency of unstained cells, an effect counteracted by 5 or 20 mM-D-glucose. The spectrum of Trypan Blue in islet-cell nuclei was red-shifted by about 20 nm. A similar red-shift was observed on adding the dye to solutions of albumin or histones, but not on mixing the dye with DNA. Binding to basic proteins may explain the concentrative uptake of Trypan Blue in dead cells and contribute to the oncogenic transformation of phagocytotically active cells. Beta-Cells in vitro are killed by alloxan and hence represent a valid model for studying the diabetogenic action of the drug.

Albumins↗

PubMed1983

Measurement of intracellular potassium ion concentrations by n.m.r.

39K n.m.r. was used to detect and quantify K+ within human erythrocytes. A shift reagent consisting of an anionic complex of dysprosium(III) with sodium tripolyphosphate permitted a distinction to be made between K+ inside and outside erythrocytes. Intracellular K+ concentrations determined by this method were similar to values obtained by flame photometry.

Dysprosium↗