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PubMed1997

Technical note: CT determination of the mineral density of dry bone specimens using the dipotassium phosphate phantom.

Recent studies have demonstrated the potential application of computed tomography (CT) in research into bone density. Clinical studies of bone density using CT commonly employ a dipotassium phosphate phantom to calibrate measurements of mineral density. Designed for in vivo studies, the use of this phantom requires that bones be scanned while immersed in and permeated by fluids or soft tissues similar to water in X-ray attenuation coefficient. However, this condition may not always be met in anthropological applications, which often involve rare and fragile specimens. This study compares mineral density values calculated for a sample of bones scanned-at the same sites-in air and in water. The results indicate that, when scanned in air, the mineral density of trabecular bone is dramatically underestimated, while that of cortical bone is slightly overestimated. We present a linear regression equation to correct this error but recommend that, when possible, researchers calculate their own regressions based on their specific scanning conditions.

Animals↗
PubMed1997

Organization of the blood and lymphatic microvasculature of the gallbladder in the guinea pig: a scanning electron microscopic study.

The organization of the blood and lymphatic microvessels of the gallbladder in the guinea pig is demonstrated by scanning electron microscopy (SEM) of vascular corrosion casts, and SEM of KOH-macerated tissues. In the lamina propria of the gallbladder, there is a dense network of subepithelial capillaries. The network is supplied by the arterioles that come off the arterial plexus located deep in the lamina propria. The network gathers into the postcapillary venules continuous with the collecting venular plexus located immediately below the subepithelial capillary network. The precapillary arterioles are sparsely surrounded by a single layer of circularly oriented extensions of smooth muscle cells. The terminal arterioles are endowed with circularly oriented fusiform smooth muscle cells. The nervous plexus is also noticed along the terminal arterioles. The capillaries are embraced by flat prolongations of pericytes. The postcapillary venules are sparsely surrounded by stellate pericytes and the collecting venules are sparsely surrounded by elongated or branched spindle-shaped, primitive smooth muscle cells which extend their long process in various directions along the vascular wall. The lymphatics are mostly located in the subserosal layer. The tips of the initial lymphatics are closed by endothelial cells, although there are frequently some gaps between them. The thin flaps of the lymphatic endothelial cells overlap or interdigitate with each other. The luminar surfaces of the lymphatics show oval nuclear protrusions, while the abluminal surfaces showed numerous microfolds except for the oval and flat nuclear portions. The lymphatics possess neither smooth muscle cells nor pericytes.

Animals↗
PubMed1999

Diesel exhaust and lung cancer mortality in potash mining.

BACKGROUND: Findings from experimental studies on rodents and from epidemiological studies suggest that diesel exhaust may cause lung cancer. There is evidence that in several occupations, e.g., truck drivers and railway workers, the risk of lung cancer increases with duration of employment, and exposure to diesel exhaust provides the most likely explanation for these elevations of risk. METHODS: We investigated the association between lung cancer mortality and exposure to diesel exhaust in a cohort study. The cohort comprised 5, 536 male potash miners who were followed from 1970 to 1994. Exposure was assessed from concentration measurements of the total carbon (i. e., elemental and organic carbon in total) in personal dust samples. The concentration values were multiplied by years of exposure to give a quantitative exposure measure. The concentration levels ranged from 0.12 to 0.39 mg/m(3) total carbon in fine dust. Work histories and smoking habit data were obtained from medical company records. Causes of death were ascertained from death certificates. RESULTS: During the follow-up period, 424 deaths were recorded, including 133 of cancer, 38 of lung cancer. The relative risk of lung cancer between two groups with high and low exposure was 2.2 (95% confidence interval 0.8-6.0). With Cox regression, we found a lung cancer relative risk 1.7 (0.5-5.8) after twenty years of exposure. Extensive scrutiny proved smoking not to be a confounder in this study. CONCLUSIONS: The principal finding of the study is a doubling of relative lung cancer risk after twenty years of exposure in the workplaces with highest exposure. However, the observed elevation is nonsignificant even at a 90% level. Further follow-up is intended to enhance the study power.

Carbon↗
PubMed1997

Stereomorphologic observation of bone tissue response to hydroxyapatite using SEM with the EDTA-KOH method.

To obtain further information on the interaction of hydroxyapatite (HA) and the bony implantation bed, 20- to 40- mesh dense HA particles were implanted into the tibiae of dogs. Following healing periods of 2 weeks, 1 month, and 3 months, the specimens were retrieved and prepared by either conventional preparatory procedures for scanning electron microscopy (SEM) of the EDTA-KOH method. Under SEM observation, the interparticular osteogenesis among HA particles progressed in a programmed sequence. Ample blood supply and osteoblasts initially presented in the interparticular space. The secretion of bone matrix resulted in the formation of immature bone. This scaffold was then transformed into mature lamellar bone during the following bone remodeling process. The serial changes closely resembled the pattern viewed in controls that did not implant HA. A spatial relationship between bone cells and HA was clearly demonstrated. In particular, the osteoblasts displayed an extremely flat appearance with many microappendages. The microappendages anchored cells to the HA surface and fused with granular material covering the HA crystals. The more characteristic cellular morphology was revealed by the EDTA-KOH method. Microscopic pictures clearly identified the three-dimensional images of ruffled borders of osteoclasts and the slender cytoplasmic processes of osteocytes. This study provided further evidence for the favorable biological response of HA to bone cells as well as the value of the EDTA-KOH method in examining the stereomorphology of bone cells.

Animals↗
PubMed1998

Influence of potassium fluoride on the syntheses of methylpiperazine-modified poly(vinyl chloride)s for use as fixed-site proton carrier membranes.

Aminated poly(vinyl chloride) (PVC) membranes were prepared that had a Nernstian response over a wide range of pH. The reaction between PVC and methyl-piperazine (MePIP) in dimethylformamide (DMF) was studied over a wide range of time and temperature, and in the presence of the catalyst, potassium fluoride (KF). Time, temperature, and KF increased the nitrogen (N) content of the resulting polymers, but sometimes at the expense of decreasing their specific viscosities (molecular weights). Activation energies of processes that occurred in different temperature ranges were estimated assuming an Arrhenius relationship. A Nernstian response occurred once the N content approached to about 0.3 w/w %, and was accelerated by the presence of KF at elevated temperatures. Increasing the N content above about 3% led to a loss of the Nernstian response either because of an increase in the double bond content and a subsequent decrease in polymer mobility, or because of a decrease in the molecular weight of the copolymer and concomitant difficulties in film preparation.

Dimethylformamide↗
PubMed1998

Crystallization kinetics of a low-expansion feldspar glass for dental applications.

Previous studies have shown that the crystallization of glasses in the system K2O-Al2O3-SiO2, in the primary field of leucite, is not possible without modification of the composition. Leucite (KAlSi2O6) is used as a reinforcing phase in some compositions for all-ceramic dental restorations. However, because of their higher coefficient of thermal expansion, these materials cannot be veneered with conventional metal-ceramic porcelains. The purposes of this study were to investigate the crystallization behavior of a glass in the system K2O-Al2O3-SiO2 and to evaluate the effect of heat treatment on the crystal size, percent crystallinity, and coefficient of thermal expansion of the material. Ion-exchanged glass powder was prepared by mixing the glass with rubidium nitrate and heat-treating at 450 degrees C for 4, 8, 24, or 48 h. Bars were made from these powders and baked under vacuum at 1038 degrees C for 2 min. The bars made from the powder ion-exchanged for 48 h were further heat-treated for 4 h at either 800 degrees C, 850 degrees C, 900 degrees C, 950 degrees C, or 1038 degrees C. X-ray diffraction analyses showed cubic leucite was the only crystalline phase in the specimens made from the powders ion-exchanged for 4, 8, 24, or 48 h and baked at 1038 degrees C for 2 min. Further heat treatment for 4 h at either 800 degrees C, 850 degrees C, 900 degrees C, 950 degrees C, or 1038 degrees C promoted the growth of cubic leucite. In addition, a second phase identified as tetragonal rubidium-leucite was present in the specimens heat-treated for 4 h at 1038 degrees C. SEM observations showed that all specimens made from the powders ion-exchanged for 48 h exhibited small spherical crystals dispersed in a glassy matrix. The percent crystallinity ranged from 18.9% to 42.9% and the average particle size was between 0.64 to 1.18 microns. The coefficients of thermal expansion ranged between 8.076 and 8.788 x 10(-6)/degree C.

Aluminum Silicates↗
PubMed1996

Isolation and characterization of glycogen synthase in Dictyostelium discoideum.

We have partially purified the protein and isolated the glcS gene for glycogen synthase in Dictyostelium. glcS mRNA is present throughout development and is the product of a single gene coding for 775 amino acids, with a predicted molecular mass of 87 kD. The sequence is highly similar to glycogen synthase from human muscle, yeast, and rat liver, diverging significantly only at the amino and carboxy termini. Phosphorylation and UDPG binding sites are conserved, with K(m) values for UDPG being comparable to those determined for other organisms, but in vitro phosphorylation failing to convert between the G6P-dependent (D) and -independent (I) forms. Enzyme activity is relatively constant throughout the life cycle: the I form of the enzyme isolates with the soluble fraction in amoebae, switches to the D form, becomes pellet-associated during early development, and finally reverts during late development to the I form, which again localizes to the soluble fraction. Deletion analysis of the promoter reveals a GC-rich element which, when deleted, abolishes expression of glcS.

Amino Acid Sequence↗
PubMed2000

Electrophoretic properties of dodecyltrimethylammonium bromide micelles in KBr solution.

Charge in ionic micelles determines the trends of their stability and their practical applications. Charge can be calculated from zeta potential (zeta) measurements, which, in turn, can be obtained by Doppler microelectrophoresis. In this study, the electrophoretic properties of dodecyltrimethylammonium bromide (DTAB) in KBr aqueous solution (0-6 mM) were determined by Doppler microelectrophoresis. At very low surfactant concentrations (up to 6 mM), zeta potential was quite constant and due to the ionized monomers (DTA+). Above 6 mM, zeta potential increased to a maximum at surfactant concentrations still below the critical micellar concentration (CMC). This increase could be explained by a formation of nonmicellar aggregates of DTAB. Then, above the CMC, zeta potential underwent an abrupt reduction, which was dependent qualitatively and quantitatively on KBr concentration, and which could be due to an increase of the number of counterions adsorbed on the micelle surface. Calculation of effective micellar charge from zeta potential gave the surface charge density. Comparing this value with the theoretical, obtained from geometrical considerations, a fraction of 0.29 of charged micellar headgroups was obtained when DTAB was in aqueous solution, which is consistent with the value obtained by conductivity measurements.

Bromides↗
PubMed2000

Study of the structure of poly(methyl methacrylate) obtained in the presence of potassium hydride.

Electrospray ionization mass spectrometry (ESI-MS) in positive- and negative-ion mode and multi-step tandem mass spectrometry (ESI-MS ( n) ) were selected for the determination of the structure of poly(methyl methacrylate) obtained using potassium hydride as initiator. Macromolecules with methoxy and methyl starting groups, i. e. those situated at the beginning of the polymer backbone, were observed in this case. No other differences in the chain structure were found in the polymer.

Catalysis↗
PubMed2001

Orthophosphate anion enhances the stability and activity of endoxylanase from Bacillus sp.

Endoxylanase, for which the optimum temperature is 60 degrees C (optimum pH 7), is labile to heat. Because the isoelectric point (pI) value of this xylanase is 10.6, the net charge of this enzyme is positive at pH 7. Thus, ions are likely to influence its enzyme structure and the thermal stability of endoxylanase may improve. Among the various ions tested, orthophosphate anion (HPO(4)(2-)) was found to significantly improve not only the stability but the activity of xylanase. When K(2)HPO(4) concentration was increased from 50 mM to 1.2 M, the T(m )value of xylanase was increased from 60.0 degrees C to 74.5 degrees C. The affinity of xylanase on xylan also increased along with K(2)HPO(4) concentration. Thus, the xylanase activity at 0.6 M K(2)HPO(4) was 2.3-fold higher than that at 50 mM K(2)HPO(4), and 120.2-fold higher than that in 40 mM MOPS buffer. This enhanced activity in the presence of K(2)HPO(4 )probably takes place because the orthophosphate anion affects the binding and catalytic residues of endoxylanase.

Anions↗
PubMed2000

A method for the determination of the hepatic enzyme activity catalyzing bile acid acyl glucuronide formation by high-performance liquid chromatography with pulsed amperometric detection.

A method for the determination of the activity of hepatic glucuronyltransferase catalyzing formation of bile acid 24-glucuronides using high-performance liquid chromatography (HPLC) with pulsed amperometric detection (PAD) has been developed. Bile acid 24-glucuronides were simultaneously separated on a semimicrobore column, Capcell Pak C18UG120, using 20 mM ammonium phosphate (pH 6.0)-acetonitrile (27:10 and 16:10) as the mobile phase in the stepwise gradient elution mode. A 1 M potassium hydroxide solution for the hydrolysis of the 24-glucuronides, which liberates the corresponding bile acids and glucuronic acid, was mixed with the mobile phase in a post-column mode, and the resulting eluant was heated at 90 degrees C, the 24-glucuronides being monitored using a pulsed amperometric detector; the limit of detection was 10 ng. The proposed method was applied to the determination of the hepatic enzyme activity catalyzing bile acid 24-glucuronide formation and the result exhibited the efficient 24-glucuronide formation of the monohydroxylated bile acid, lithocholic acid.

Acetonitriles↗
PubMed2001

Potassium nitrate toothpaste for dentine hypersensitivity.

BACKGROUND: Dentine hypersensitivity may be defined as the pain arising from exposed dentine, typically in response to external stimuli, and which cannot be explained by any other form of dental disease. Many treatment regimes have been recommended over the years, and in recent years particular attention has been focused on toothpastes containing potassium nitrate. OBJECTIVES: To compare the effectiveness of potassium nitrate containing toothpastes with placebo toothpastes in reducing dentine hypersensitivity. SEARCH STRATEGY: The following databases were cross searched via the database host DIALOG: MEDLINE, EMBASE, ELSEVIER BIOBASE, BIOSIS PREVIEWS, CAB HEALTH, SCI SEARCH, CURRENT CONTENTS until 1 April 2000. The specialised Cochrane Oral Health Group Trials Register was also searched. Bibliographies of clinical studies and reviews identified in the electronic search were checked for studies published outside the electronically searched journals. SELECTION CRITERIA: Randomised clinical trials (RCTs) in which the effect on dentine hypersensitivity of potassium nitrate toothpastes were tested against non-potassium nitrate containing placebo toothpastes. DATA COLLECTION AND ANALYSIS: Two of the reviewers independently recorded the results of the included trials using a specially designed chart. Sensitivity was assessed by using thermal, tactile, air blast, and subjective methods. The quality of all RCTs, that fulfilled the inclusion criteria, was acceptable with Jadad scores ranging from 3 to 4 (Jadad 1998). MAIN RESULTS: Out of the eight studies that initially fulfilled the criteria to be included in the review, four studies did not present mean and standard deviations and could thus not be included in the meta-analysis. Three of these did not show an effect on any of the measurements of dentine hypersensitivity, while one did. Four studies were included in the meta-analysis which showed statistically significant effect of potassium nitrate toothpaste on air blast and tactile sensitivity, e.g. the meta analysis of air blast sensitivity showed a standardized mean difference in sensitivity score of -1.51 (95% CI: -2.09 to -0.94) in favour of treatment. The subjective assessment failed to show a significant effect at the six to eight week assessment. REVIEWER'S CONCLUSIONS: No strong evidence is available supporting the efficacy of potassium nitrate toothpaste for dentine hypersensitivity.

Adult↗
PubMed2006

Potassium containing toothpastes for dentine hypersensitivity.

BACKGROUND: Dentine hypersensitivity may be defined as the pain arising from exposed dentine, typically in response to external stimuli, and which cannot be explained by any other form of dental disease. Many treatment regimens have been recommended over the years, and in recent years particular attention has been focused on toothpastes containing various potassium salts. OBJECTIVES: To compare the effectiveness of potassium containing toothpastes with control toothpastes in reducing dentine hypersensitivity. SEARCH STRATEGY: The following databases were searched: Cochrane Oral Health Group Trials Register (searched until August 2005); CENTRAL (until August 2005); EMBASE/MEDLINE, PubMed, Web of Science (until September 2005). Bibliographies of clinical studies and reviews identified in the electronic search were checked for studies published outside the electronically searched journals. SELECTION CRITERIA: Randomised controlled trials (RCTs) in which the effect on dentine hypersensitivity of potassium containing toothpastes was tested against non-potassium containing control toothpastes. DATA COLLECTION AND ANALYSIS: Two of the review authors independently recorded the results of the included trials using a specially designed form. Sensitivity was assessed by using thermal, tactile, air blast, and subjective methods. MAIN RESULTS: Six studies were included in the meta-analysis which showed the statistically significant effect of potassium nitrate toothpaste on air blast and tactile sensitivity at the 6 to 8 weeks follow up, e.g. the meta-analysis of air blast sensitivity showed a standardized mean difference in sensitivity score of -1.25 (95% CI: -1.65 to -0.851) in favour of treatment. The subjective assessment failed to show a significant effect at the 6 to 8 week assessment. AUTHORS' CONCLUSIONS: The evidence generated by this review is based on a small number of individuals. Furthermore, the effect varies with the methods applied for assessing the sensitivity. Thus no clear evidence is available for the support of potassium containing toothpastes for dentine hypersensitivity.

Adult↗
PubMed2006

Interventions for cutaneous molluscum contagiosum.

BACKGROUND: Molluscum contagiosum is a common skin infection, caused by a virus, which will usually resolve within months in people with a normal immune system. Many treatments have been promoted for molluscum contagiosum but a clear evidence base supporting them is lacking. OBJECTIVES: To assess the effects of management strategies (including waiting for natural resolution) for cutaneous, non-genital molluscum contagiosum in healthy people. SEARCH STRATEGY: We searched the Skin Group Specialised Register (March 2004), the Cochrane Central Register of Controlled Trials (2004, Issue 2), MEDLINE (from 1966 to March 2004), EMBASE (from 1980 to March 2004) and LILACS (from 1982 to March 2004) databases. We also searched reference lists and contacted pharmaceutical companies and experts in the field. SELECTION CRITERIA: Randomised controlled trials for treatment of molluscum contagiosum were investigated. Trials on sexually transmitted molluscum contagiosum and in people with lowered immunity (including those with HIV infection) were excluded. DATA COLLECTION AND ANALYSIS: Study selection and assessment of methodological quality were carried out by two independent authors. As similar comparisons between two interventions were not made in more than one study, statistical pooling was not performed. MAIN RESULTS: Five studies, with a total number of 137 participants, examined the effects of topical (three studies), systemic and homoeopathic interventions (one study each). Limited evidence was found for sodium nitrite co-applied with salicylic acid compared to salicylic acid alone (risk ratio (RR) 3.50, 95% confidence interval (CI) 1.23 to 9.92). No statistically significant differences were found for topical povidone iodine plus salicylic acid compared to povidone iodine alone (RR of cure 1.67, 95% CI 0.81 to 3.41) or compared to salicylic acid alone. Also no statistically significant differences were found for potassium hydroxide compared to placebo; systemic treatment with cimetidine versus placebo or systemic treatment with calcarea carbonica, a homoeopathic drug, versus placebo (RR 5.57, 95% CI 0.93 to 33.54). Study limitations included no blinding (two studies), many dropouts (three studies) and no intention-to-treat analysis (two studies); small study sizes may have led to important differences being missed. None of the evaluated treatment options were associated with serious adverse effects. AUTHORS' CONCLUSIONS: No single intervention has been shown to be convincingly effective in treating molluscum contagiosum.

Anti-Infective Agents, Local↗
PubMedDate not supplied

Kinetic spectrophotometric determination of rutin by its inhibitory effect on the oxidation of amaranth by potassium periodate.

A novel kinetic spectrophotometric method is described for the determination of rutin. The method is based on the inhibitory effect of rutin on the oxidation reaction of amaranth by potassium periodate in acidic media at 100 degrees C. The linear range for the determination of rutin is 0.02 - 0.50 microg/ml, and the detection limit is 0.014 microg/ml. The method has been successfully applied to the determination of rutin in medicine of rutin tablet and traditional Chinese medicine.

Amaranth Dye↗
PubMed1981

Arsenic-related hepatic angiosarcoma.

Data from several small autopsy series in German vintners in the 1940s and 1950s and a number of case reports have previously suggested that arsenic is a cause of hepatic angiosarcoma (HAS). In a nationwide review of deaths from HAS in the United States, we identified seven cases with a history of prolonged use of Fowler's solution (inorganic potassium arsenite), which provide further support for the association of arsenic exposure and HAS. An epidemiologic study of a cohort of individuals treated long-term with Fowler's solution might confirm this association.

Adult↗