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PubMed1999

Quantitation of fluorescent nucleotide incorporation by capillary gel electrophoresis and laser-induced fluorescence detection.

A method has been developed by which enzymatically incorporated fluorophore-labeled nucleotide sites in nucleic acid can be quantitated by degradation of nanogram quantities of DNA followed by capillary gel electrophoretic analysis with fluorescence detection. In this way the differing relative labeling densities achieved using either C5-substituted dUTP's or N4-substituted dCTP's were determined. The method has proven to be very useful in obtaining quantitative analytical data from the small quantities of complex molecules produced in nick translations. Various polymerization conditions using DNA polymerase I were examined to determine optimal labeling density. Simultaneous copolymerization of green fluorescing dCTP and dUTP nucleotides were undertaken in an attempt to maximize labeling density.

DNA↗

PubMed1995

From single-substance evaluation to ecological process concept: the dilemma of processing gold with cyanide.

In the past decades, limit concentration values for environmentally dangerous synthetic and natural chemical substances have been established in industrialized countries. Depending on the range of application, state of aggregation, propagation velocity, specific action on living organisms, long- or short-time effect, etc., different terms are used to specify these limit concentrations (acceptable daily intakes, TLV, LD50, emission values, water quality standards, etc.). Several parameters (e.g., range of application, ethic and social valuation, environmental factors, scientific knowledge) have led to nationally and internationally varying values depending on the region and time. The accuracy of this system of evaluation cannot necessarily be improved by listing further analytical data, but rather by furnishing sufficiently secured scientific data for a serious discussion, with the public concepts influenced more and more by the mass media. The best-established scientific knowledge has been acquired by the chemical industry. National and international groups demand that ecological-chemical problems in other fields of industry be dealt with as well; this research should, without doubt, be intensified. The example of the mining industry, which must employ chemical methods to isolate small concentrations (ppm), demonstrates the environmental conflict caused by the increasing world population, requiring the adaptation of the process by industry to the modern environmental concept. This is illustrated by the evolution of the gold recovery process.

Animals↗

PubMed1999

Modification of Surface Charge Properties during Kaolinite to Halloysite-7Å Transformation.

The surface charge properties of well and poorly ordered kaolinite and halloysite-7Å, representing three different stages of kaolinite to halloysite-7Å transformation identified in the kaolin deposit of São Vicente de Pereira (Portugal), were studied. Mineralogical (X-ray diffraction, Fourier transformation-infrared) and chemical data (analytic electron microscopy) showed that the gradual transformation from kaolinite to halloysite-7Å minerals was accompanied by an increase in hydration and a decrease in Si/Al ratio. In particular, the replacement of Si(IV) by Al(III) in the tetrahedral layer caused an electrical charge unbalance and a modification of surface charge properties during the kaolinite to halloysite transformation. Accordingly, the cation exchange capacity (CEC) gradually increases when passing from well-ordered kaolinite to halloysite-7Å, attesting the direct correspondence existing among the structural order of the samples, number of tetrahedral substitutions, and CEC. Electrophoretic experiments provided further evidences of the origin of surface charge properties and the variation encountered during kaolinite to halloysite-7Å transformation. The curves of zeta-potential versus pH show the same pH dependency for the three minerals, but a gradual increase of zeta-potential when passing from well ordered kaolinite to halloysite-7Å through the poorly ordered kaolinite. The results can unambiguously be attributed to the increase of permanent charge due to the higher degree of isomorphic substitution, more than to the increase of structural and ionizable water. Copyright 1999 Academic Press.

Journal Article↗

PubMed2001

Effects of changes in experimental design on PET studies of isometric force.

Based on single-cell recordings in primates, the relationship between neuronal activity and force magnitude is thought to be monotonic, at least for a subset of pyramidal cells in the motor cortex. Functional neuroimaging studies have also suggested a monotonic relationship between cerebral activation and force magnitude. In order to more precisely define this relationship and to characterize the activation pattern(s) associated with the modulation of static force, we studied 40 normal subjects using [(15)O]water PET and a simple visuomotor task-application of static force on a micro force sensor with the thumb and index finger of the right hand. When our experimental design did not produce the expected result (evidence of a relationship between cerebral activation and force magnitude in ten subjects), we made serial changes in the experimental protocol, including the addition of control (baseline) trials, and increased the number of subjects in an effort to increase our sensitivity to variations in force magnitude. We compared univariate and multivariate data-analytic strategies, but we relied on our multivariate results to elucidate the interaction of attentional and motor networks. We found that increasing the number of subjects from 10 to 20 resulted in an increase in statistical power and a more stable (i.e., more replicable) but qualitatively similar result, and that the inclusion of control trials in a 10-subject group did not enhance our ability to discern significant brain-behavior relationships. Our results suggest that sample sizes greater than 20 may be required to detect parametric variation in some instances and that failure to detect such variation may result from unanticipated neurobehavioral effects.

Adult↗

PubMedDate not supplied

Volatile N-nitrosamines in mainstream cigarette smoke: occurrence and formation.

Analytical data is presented for the occurrence of the three major volatile N-nitrosamines in cigarette tobacco and mainstream smoke, namely N-nitrosodimethylamine (NDMA),- N-nitrosoethylmethylamine (NEMA) and N-nitrosopyrrolidine (NPYR) as well as for the occurrence of the corresponding precursor amines and non-volatile N-nitrosamino acids in tobacco. Experimental studies using the C20 reference cigarette show that NPYR present in mainstream smoke results from direct transfer of preformed NPYR (ca. 1.5%), decarboxylation of N-nitrosoproline in tobacco (ca. 10%), pyrolytic nitrosation of pyrrolidine in tobacco (ca. 37%) and concerted decarboxylation/nitrosation of proline (ca. 52%) during tobacco pyrolysis.

Chromatography, Gas↗

PubMed1994

Mono-ortho- and non-ortho-substituted polychlorinated biphenyls in human milk from Mohawk and control women: effects of maternal factors and previous lactation.

Fifty-four individual human milk samples from 50 mothers (20 Mohawks and 30 controls) were analyzed for four non-ortho- and eight mono-ortho-substituted polychlorinated biphenyls (PCBs). Mean total coplanar PCBs concentrations were 49 ng/g and 55 ng/g lipid for Mohawk and control women, respectively. A statistical evaluation of all analytical data reveals no significant difference of total coplanar PCB level between Mohawk and control women. The level of these contaminants is influenced by the age of the mother, number of breastfed children, and length of nursing period. Older women, primiparae, and cigarette smokers had higher levels of coplanar PCBs. In general, women had higher levels of coplanar PCBs in the first lactation and in the earlier samples of a given lactation, while levels declined both with duration of breast-feeding and with number of children nursed. The contribution of individual non-ortho- and mono-ortho-substituted PCB congeners to the total calculated toxic equivalent values (sigma TEQ) was assessed for the breast milk samples. The levels of polychlorinated dibenzo-p-dioxins (PCDDs) and polychlorinated dibenzofurans (PCDFs) in human milk of pooled specimens from Los Angeles, California and Binghamton, New York, widely separate cities in the United States (Schecter et al. 1989), were presented for reference purpose. The main contributions to the sigma TEQ were PCB congeners #118 (25.8 pg/g lipid), #126 (25 pg/g lipid), #105 (10.8 pg/g lipid), and #156 (7.4 pg/g lipid). Collectively, these compounds accounted for 70% of the sigma TEQ values.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1985

Purification of the NusB gene product of Escherichia coli K12.

The nucleotide sequence of the entire nusB gene of Escherichia coli has recently been determined and the amino acid sequence of its product deduced (Ishii et al. 1984; Swindle et al. 1984). The NusB protein was purified by chromatography on Sephadex G-100, phosphocellulose and hydroxylapatite. Purification of the protein was monitored using 14C-labelled NusB protein, which was synthesized in a maxicell containing an nusB plasmid as a marker. The final product, which was at least 95% pure as judged by polyacrylamide gel electrophoresis in the presence of sodium dodecyl sulphate, had a molecular weight of about 16,000 and an isoelectric point of about 7.3. Analytical data on the amino acid composition of the purified protein agreed with that deduced from the DNA sequence and indicated that this protein was indeed the product of the nusB gene.

Amino Acid Sequence↗

PubMed1990

The development and application of ultrastructural research in mycology.

Electron microscopy has contributed a great deal to the field of mycology. Fungal ultrastructure has been, and continues to be, a key research element in the study of spore development and germination, host-pathogen interactions, nuclear behavior, and studies of subcellular organelles and organization linking structure and function. Since the earliest research in transmission electron microscopy in the 1950s, mycologists have kept pace with the developments in all areas of electron microscopy and have used them to great advantage in generating fine structural information on fungi. These recent developments include the use of scanning electron microscopy in the 1960s, X-ray microanalysis, cryopreservation and immunoelectron microscopy in the 1970s and 1980s. All of these techniques will continue to provide mycologists with the means to gain morphological and analytical data at the ultrastructural level.

Cryopreservation↗

PubMed1977

[Quantitative isolation of acid mucopolysaccharides from urine in progressive scleroderma (author's transl)].

After filtration the urine was concentrated to about 1/10 of the original volume. The urine was centrifuged for 15 min at 5000 rev/min. The supernatant was chromatographed on Bio-Gel P-2-with a 10% aqueous solution of ethanol. Then the glycosaminoglycan fraction was separated into seven further fractions by chromatography on Dowex 1 X 2 and elution with increasing concentration of sodium chlorid. The desalted fractions were analysed. From the analytical data presented no definite correlation between excretion of glycosaminoglycans in urine and progressive scleroderma can be observed. These results were discussed with further data presented by Hexosamine determination.

Glycosaminoglycans↗

PubMed1979

[A fatal monointoxication by flurazepam (Dalmadorm). Problems of the toxicological interpretation (author's transl)].

A death case following a suicidal overdose of flurazepam (Dalmadorm) is reported. The body was found after 3 month near a highway. The course of the intoxication is in question as benzodiazepines are believed to be relatively save drugs. The death might have occured rapidly because of the acute toxic actions of the drug overdose as well as after a protracted course involving additional complications like inflammatory alteration of the myocard or hypothermia during a coma. Flurazepam and its major metabolites were analysed in blood and urine. The toxic levels of flurazepam (0.51 mg/l), N1-desalkylflurazepam (0.14 mg/1) and N1-hydroxyethylflurazepam (9.0 mg/1) in the blood amounted to 20--50 times higher than therapeutic levels, with flurazepam and metabolites being in only slight altered relation to each other. The overdose is considered to have been above 2.4 g (80 tablets). The resorption of the drug was complete. The analytical findings in blood and urine as well as in the GI-tract are in satisfactory agreement. The analytical data of flurazepam and its metabolites are discussed in detail, taking metabolic and pharmacokinetic parameters, autopsy findings and case circumstances into consideration. A final decision about the course of the intoxication is not possible. This case shows however the fatal consequences of a flurazepam overdose although alcohol or other drugs were not involved.

Autopsy↗

PubMed1985

Analysis of vaterite microspherolith deposits on a pure cholesterol gallstone by X-ray diffraction, X-ray microanalysis and infrared absorption techniques.

Minute globular concretions of light-green and light-brown colour were found as deposits in the pits at the rough surface of a pure cholesterol gallstone. They were analyzed by scanning electron microscopic, X-ray diffraction, X-ray microanalytical and infrared absorption spectrometric methods. In scanning electron microscopy, the concretions appeared as ovoid microspheroliths varying from 5 to 30 micron in size. The microspheroliths presented smooth and rough surfaces; the reason for these different types of surface remained unclear. X-ray diffraction and infrared absorption analysis revealed that the microspheroliths were mainly composed of vaterite and the host plate-like crystals were cholesterol. By energy-dispersive X-ray microanalysis, large quantities of calcium without significant quantities of phosphorus were detected in the microspheroliths. Calcium was absent in the plate-like crystals and could not be detected in the central part of the stone. In the pigmented periphery of the stone, some silicon and iron were found. The presence of calcite, aragonite and iron-containing pigment materials in the concretion is suggested. From the textural point of view, the analytical data strongly suggest that the stone-forming conditions suddenly changed from a cholesterol-favourable stasis condition to a condition favoring the deposition of calcium carbonate possible as the result of haemorrhage.

Absorption↗

PubMed1988

Estimates on the intake of food additives in Finland.

An estimation of the intakes of 30 food additives in Finland was conducted combining analytical data, food balance sheets, import and export statistics. The results indicated that most calculated average food additive intakes were well below the ADI values and internationally at an acceptable level. The intakes of nitrates, nitrites, saccharin and cyclamates were above or close to the respective ADI values. More studies are planned on these substances in order to establish possible special risk groups.

Diet↗

PubMed1991

The origin of high cadmium loads in some bivalve molluscs from Shark Bay, Western Australia: a new mechanism for cadmium uptake by filter feeding organisms.

Although Shark Bay is remote from all known industrial and geological sources of heavy metals, the cadmium content of several species of Shark Bay molluscs may exceed 10 mg/kg. The cadmium load in these molluscs varies geographically within the bay, but possible explanations for cadmium distribution involving variation in salinity, saline groundwater influx, the dissolved cadmium concentration, the cadmium concentration in substrate sediments, species, or an anthropogenic source are not supported by analytical data. The cadmium concentration is normal in Shark Bay seawater (0.04 microgram/L to about 0.35 microgram/L), rarely exceeds 0.25 microgram/L in ground waters, bore waters, and salt lake brines, and very seldom exceeds 1 mg/kg in sediments. No direct link between the cadmium loads in molluscs and its concentration in the water or substrate sediment is evident, but the cadmium load in molluscs is usually highest where turbulence is high and the substrate sediment contains fine hematite. Over about 2,000 km2, the water depth in Shark Bay is less than 1 m and fine sediment is readily suspended by strong winds. The iron-oxides (superfine hematite) are eroded from the Peron Sandstone exposed in some coastal cliffs and constitute up to 2% of substrate sediments near these cliffs. This study reveals that cadmium in the water adsorbs extremely efficiently onto the surface of the hematite, which is negatively charged at the prevailing seawater pH of 8.15, and that suspended hematite particles are ingested by the molluscs. Inside the molluscs, lower pH conditions cause reversal of the hematite charge and the cadmium is released and accumulated by the organism.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

A methodological review of "method skeptic" reports.

The literature purporting to demonstrate that clinical neuropsychology is of limited validity in the forensic setting is reviewed critically and alternative interpretations are discussed. The methodological, procedural, conceptual, data analytical and survey/research design limitations are evaluated.

Female↗

PubMed1978

Studies on enzymic browning of potatoes (Solanum tuberosum). IV. Relationship between tyrosine turnover and rate of browning.

Using analytical data from the literature the tyrosine turnover was calculated by a method published previously by us for 72 potato samples with different rates of browning. The samples included 9 varieties grown at three locations in 1969, which were analysed after harvest and after different times of storage at three temperatures. For 58 samples (81%) this calculation led to the same classification of the varieties as did visual observation of the rate of discolouration. It is concluded that enzymic browning of potatoes is correlated rather with tyrosine turnover, which depends on the concentrations of phenol oxidase, tyrosine, chlorogenic acid, and ascorbic acid, than with any single parameter.

Ascorbic Acid↗

PubMed1975

The levels of heavy metals (Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, Hg) in fish from onshore and offshore waters of the German bight.

With the intention of increasing our knowledge about the actual degree of heavy metal accumulation in fish, the contents of the elements manganese, iron, cobalt, nickel, copper, zinc, cadmium, lead and mercury in certain fish species (cod and plaice) from onshore and offshore waters of the German Bight have been determined. The measurements have been performed by atomic absorption spectrophotometry: Flame AAS was used as investigating procedure for the determination of Mn, Fe, Cu and Zn. A non-flame atomization system with a heated graphite tube was used for the determination of Cd, Pb, Co, and Ni. The concentration of total Hg was estimated according to the so-called "cold vapour atomic absorption method". In order to avoid errors in interpretation of measured values of Co and Ni, which occured as a result of matrix effects, a special technique has been developed. This based upon an selective separation and enrichment by chelate exchanger chromatography ("Chelex 100"). The analytical data obtained are plotted in a diagram with log.-log. scale. The content is shown on the x-axis, and the corresponding relative reproducibility (variation coefficient) of the method used is shown on the y-axis. For all elements investigated certain levels have been found out. From an examination of the results it appeared that there were comparatively small differences in the prevailing concentrations of transition metals Mn, Fe, Co, Ni, Cu, and Zn between samples of the same species from different areas. Likewise, the levels estimated for plaice did not differ from those estimated for cod. There is some evidence of elevated levels of Cd, Pb, and Hg in plaice from areas along the coastline.

Animals↗

PubMed1990

Nitrate, nitrite, and N-nitroso compounds in Finnish foods and the estimation of the dietary intakes.

An estimate of the dietary intakes of nitrite, nitrate and N-nitroso compounds is presented, based on the analytical data supplied by the Finnish Food Quality Control. Figures on the food consumption of the Finnish population, taken from a national dietary survey, and food consumption of 1768 children and adolescents over a 48-h recall period were used. The mean daily dietary nitrate intakes were estimated to be about 55 mg for the total population and for children and adolescents. The mean nitrite intakes were 1.88 mg for the total population and 1.07 mg for children and adolescents. The intake of N-nitroso compounds (NDMA) was estimated to be 0.08 micrograms for the total population and 0.02 micrograms for children. Nitrates were found to originate mainly from vegetables (80%), nitrites from meat products (97%) and nitrosamines mostly from fish products and beer. A comparison of the estimate of dietary intake of with ADI values indicated that the nitrite intake of the total population was 23% and by children 39% of ADI. The average weight was approximately 60 kg for adults and 20 kg for children. When measured average weight (39 kg) was used, and the nitrite intake was found to be 28% of ADI. Nitrate intakes from food additives were 2.5% and 1.4% of the ADI value, respectively. When the total nitrate intake from various food sources was compared with the ADI (which is given only for food additives), the estimated nitrate intake of the total population was 25% and that of children 28% of the ADI value.

Adolescent↗

PubMed1995

Comparison between ion chromatography and a spectrophotometric method for determination of nitrates in meat products.

Ion chromatography and colorimetry were used to determine nitrate ion concentration in 76 different pork meat products (salami, mortadella, wurstel, raw and cooked ham and other whole-muscle cooked products) and the results were compared. The comparison revealed that the two techniques yield quantitatively similar results, except in cases where the matrix was so complex that it might have influenced the analytical data. These results are consistent with those obtained by other authors who used UV spectrophotometric detection.

Animals↗