Visible Contamination Research Articles

Insulin and insulin-like growth factor I in follicular fluid after induction of ovulation in women undergoing in vitro fertilization.

This study was undertaken to evaluate the relationship between concentrations of insulin and insulin-like growth factor I (IGF-I) in follicular fluid and fertilization and cleavage of human oocytes fertilized in vitro. The concentration of oestradiol, progesterone, luteinizing hormone, follicle-stimulating hormone, testosterone, insulin and IGF-I was determined in 36 follicular fluids, free of visible blood contamination and containing mature oocyte-corona-cumulus complexes, obtained from 12 women undergoing in vitro fertilization. Follicular development was induced by clomiphene citrate and human menopausal gonadotrophin, and follicular aspiration was performed 35 h after an ovulatory dose of human chorionic gonadotrophin. Concentrations of IGF-I were significantly higher in follicular fluids associated with mature oocytes that fertilized and cleaved, than in follicular fluid associated with mature oocytes that did not fertilize (P < 0.001). There was no difference in the concentration of insulin between follicular fluids from which fertilized oocytes were obtained and those with oocytes that remained unfertilized. No significant correlations were found between rates of embryo cleavage, concentrations of insulin and IGF-I. Multiple linear regression analysis demonstrated that the concentrations of IGF-I in follicular fluid were predicted statistically by a negative regression coefficient for the concentration of testosterone, and by a positive regression coefficient for the concentration of progesterone in follicular fluid. No candidate variable was included in the model to predict concentrations of insulin. These data suggest an important role for IGF-I in the mature follicle.

Fungal contamination of mini peak flow meters

Sixteen peak expiratory flow meters from the Outpatient Department of Solihull Hospital were dismantled for inspection and washing. Fungal contamination was found in all 16 machines with visible contamination in four.

Infection risks from electrically operated breast pumps

Using formula milk seeded with Staphylococcus epidermidis as indicator, bacteria were observed to pass beyond the collecting bottles of three electrically operated breast pumps. Bacteria were recovered from sites distal to the level of visible contamination, the incidence increasing with repeated use of the apparatus. Despite use of a sterile collecting bottle, retrograde contamination of freshly collected milk may occur from previously contaminated components of the pumps. The results suggest that a terminal in-line air filter is essential to ensure aerosols containing potentially pathogenic bacteria do not contaminate the suction source or be emitted to the environment with the exhaust air. Where a single pump is used by more than one person adequate sterilization of all removable components is essential.

Resuscitation of carbon-contaminated mirrors and gratings by oxygen-discharge cleaning 1: Efficiency recovery in the 4–40-eV range

The dc oxygen-discharge cleaning of optical elements contaminated by synchrotron radiation has been studied for a variety of contamination levels, optical materials, electrode and reflecting-surface configurations, discharge powers, and exposure times. Cleaning with a proper electrode-surface configuration resulted in the removal of contaminant layers within 1 h even for highly contaminated elements. The reflectance of mirrors and the diffraction efficiency of gratings were almost completely restored after cleaning over the 4-40- eV energy range; the enhancement even amounted to 1 order of magnitude in some cases. This cleaning procedure did not cause any increased roughness; rather, it resulted in a reduced scattering level of contaminated elements. The removal of contaminants also led to a restoration of the grating blaze; essentially, this contributed to an improvement in the inside first-order efficiency around the blazed energy. From the results with controlled power and exposure time, it was shown that an optimum exposure is achieved within several minutes after the disappearance of visible contamination.

Catalytic activation of cobalt induced by oxidizing treatments in the methanation of carbon dioxide

A ribbon of Co catalyzing CO 2 hydrogenation at atmospheric pressure and temperatures ranging from 200 to 500 °C has been taken as an example for studying the activating effect of pre-oxidation upon the activity of metals in hydrogenation reactions. The chemical state of the Co surface could be determined at any time by direct and quick transfer of the sample from the reactor into the ultrahigh vacuum chamber of an electron spectrometer. After cleaning and prolonged exposure to H 2 (15 h, 1 bar, 500 °C) the sample displayed no visible activity up to 500 °C despite the absence of any visible contaminant on its surface. Activities ranging over several orders of magnitude could be induced in the metal by adequate pre-oxidations according to their severity. A large part of this activation was transient and its progressive decay required periods of time which were longer the more severe the pre-oxidation and the lower the temperature of reaction. The activity at any time after treatment was shown to depend not only on the oxidation but also on the subsequent reduction, since an increase of the rate of reduction resulted in a corresponding though transient increase of the activity. Reduction of most of the surface region was shown to occur very quickly, whereas deeper layers continued to reduce during the progressive decay of the activity. No visible contamination occurred during deactivation. The activation is interpreted in terms of the creation of surface defects by the alternate oxidations and reductions whereas the deactivation is considered to originate in the thermal restructuring of the surface.

THE PERSISTENCE OF OIL STRANDED ON SEDIMENT SHORELINES

ABSTRACT The objectives of this field experiment were to observe the behavior and measure the residence times of crude oil and mousse applied to a wide range of shorelines. The range of residence times measured (from 3 days to more than 1 year), depended on the energy level, drainage, and sediment textural gradients. As would be expected, self-cleaning was generally faster on more exposed or waterlogged sandy beaches than on sheltered, muddy shores. Wet weather, the presence of microflora, and burial by sediments all affected the ease of visual identification of oil. Estimates of residence times from hydrocarbon analysis were therefore longer than those based on visual survey, except where large, immobile pebbles were oil coated. However, the two estimates produced a similar rank order of residence time. Mousse treatments resulted in more patchy oil distribution and less deep but more variable infiltration than did the crude oil. Visible contamination by the mousse was longer lasting and more obvious. Some oil treatments increased the firmness of the surface sediments and may thus have increased oil residence time. Poor drainage provides hydrological protection for sediments by limiting oil adherence and penetration, which is more or less independent of sediment type, compaction, and degree of exposure. Agreement with a published vulnerability index was otherwise good.

Radiochemical method for the isolation of protactinium

A simple, yet highly reproducible separation procedure for isolating low levels of protactinium /pico- to micrograms/ from gram quantities of natural or activated soils or sediments has been developed. The reliability is achieved by minimizing the tendency of Pa to hydrolyze or to form colloids by keeping it complexed at all times either by fluoride or sulfate ions. The procedure consistently gives high chemical yields /85+8%/ and the final fractions are not only radiochemically pure, but show little or no visible mass contamination with evaporation.

The mitotic spindle of Chinese hamster ovary cells isolated in taxol-containing medium.

Mitotic spindles from Chinese hamster ovary (CHO) cells were isolated and purified by a one-step procedure in an isolation medium containing the microtubule-stabilizing drug, taxol. Released mitotic spindles were examined by phase-contrast, polarizing and differential-interference microscopy. They were also stained with monoclonal antibody raised against yeast tubulin and examined by epifluorescence microscopy. The spindles were free from visible cytoplasmic contaminants and the chromosomes were generally lost from the preparations. Electron microscopy showed that microtubules were the dominant structural component and sodium dodecyl sulphate/gel electrophoresis showed that tubulin was the major molecular species present, although a number of minor components, possibly representing microtubule-associated proteins (MAPs), were present. The taxol procedure was also useful in obtaining other microtubule-containing structures such as the midbody or the cytoplasmic microtubule complex in interphase cells. The taxol procedure was also used to isolate mitotic spindles from HeLa cells. The HeLa spindles stained positively with an antibody specific for the 210 X 10(3) Mr microtubule-associated protein, indicating that the MAP was retained by the taxol procedure. The taxol procedure appears to be of great advantage in large-scale preparations of spindles for biochemical analysis.

Plant Tissue Culture

Research Article| December 01 1981 Plant Tissue Culture Patricia Pietropaolo Patricia Pietropaolo Search for other works by this author on: This Site PubMed Google Scholar The American Biology Teacher (1981) 43 (9): 508–512. https://doi.org/10.2307/4447372 Views Icon Views Article contents Figures & tables Video Audio Supplementary Data Peer Review Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Cite Icon Cite Search Site Citation Patricia Pietropaolo; Plant Tissue Culture. The American Biology Teacher 1 December 1981; 43 (9): 508–512. doi: https://doi.org/10.2307/4447372 Download citation file: Ris (Zotero) Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentThe American Biology Teacher Search This content is only available via PDF. Copyright 1981 The National Association of Biology Teachers Article PDF first page preview Close Modal You do not currently have access to this content.

Scanning Auger microprobe study of gold–nickel–copper diffusion in thin films

The gold–nickel–copper system, with nickel the intended diffusion barrier, has been used extensively in the electronics industry for wire spring connectors, thin films on ceramic, and connectors on printed circuit boards. Although no visible contamination can be seen on the surface of the gold, poor bonding or high contact resistance frequently occurs. It has been assumed that some grain boundary diffusion of nickel has been occurring through the 2 μm gold film. A scanning Auger microanalysis was conducted on the surface and in depth on the thin film structure before and after heating at 300 °C for 4 h. Two-dimensional Auger analysis, after heating, showed the nickel to be distributed along the grain boundaries on the surface of the gold film. Subsequent Auger depth profiling showed the nickel layer to be oxidized and approximately 50 Å in depth. This characterization has led to improved understanding of the bonding problems and variation of contact resistance with this metallization system.

Isolation and purification of myotube and myoblast nuclei from cultures of embryonic chick skeletal muscle

Abstract Methods are described for the preparation of purified myotubes from embryonic chick skeletal muscle cultures and the preparation of purified nuclei from both myotubes and myoblasts. Myotubes are released from the culture dish by digestion of their collagen substratum with collagenase, and purified by sucrose density gradient sedimentation. Nuclei are prepared from the isolated myotubes by controlled homogenization in Ca2+-free medium and sedimentation through 2.1 M sucrose. Nuclei are prepared from cultured myoblasts in a similar fashion, with the inclusion of the non-ionic detergent NP-40 in the homogenization medium and sedimentation through 2.4 M sucrose. Phase contrast microscopic examination showed that the nuclear preparations are free of visible cytoplasmic contamination, and are morphologically similar to nuclei observed in situ. Biochemical assays (protein/DNA and RNA DNA ratios) confirm the purity of the nuclear preparations. Both nuclear preparations have been used to prepare purified chromatin which has spectral and chemical properties similar to those reported for chromatin purified directly from several chick tissues.

Simple method of improving the quality of platelet concentrates and the importance of production control.

Some technical improvements of the method to prepare platelet concentrates (PC) have been developed. The contamination of the PC with red blood cells (RBC) and white blood cells (WBC) is thereby kept at a low level. A majority of routinely prepared PC did not show any visible RBC contamination which means that they contained less than 0.4 X 10(9) RBC per PC unit. None of the tested examples contained more than 1 X 10(9) RBC per PC unit. The WBC contamination was less than 0.1 X 10(9) cells per PC unit in 75 per cent of tested examples and did not exceed 0.6 X 10(9) cells per PC unit. Routine platelet counting by thrombocounter applied on samples from all PRPs was found to be a reasonably simple way to make routine PC quality control. By sufficient supervision of the details of the procedure the main yield can be maintained at about 100 X 10(9) cells per unit. By follow-up of the weekly yield any deterioration of production efficiency can easily be detected.

Metabolic instability of myelin protein and proteolipid fractions.

Turnover of protein components of myelin in vivo was shown to be comparable to that of other brain proteins. Myelin was purified, to remove soluble contamination, by water shock (fraction M2) and centrifugation on sucrose and CsCl gradients. These methods gave two fractions, one of which consisted of characteristic myelin membranes free of visible contamination (M3), and the second consisted of fragmented membranes and vesicles (M4).Incorporation following intracisternal injection of [14C]lysine occurred at later time periods in myelin compared to mitochondria, probably as a result of different rates for penetration of precursor. The half‐lives for the different categories of protein and proteolipid components prepared by Triton X‐100 acetate procedures were markedly heterogeneous. In myelin, the highest incorporation occurred in the soluble basic proteins with half‐lives of 14‐21 days (fraction III), followed by the interface (Folch‐Lees, fraction II) material with half‐lives of 12–24 days, and the insoluble proteins (Wolfgram, fraction III) with half‐lives of 28–32 days. The half‐lives varied with the pulse period used (15–360 min) and give evidence of both short‐lived and long‐lived proteins. Heterogeneity of turnover was supported by the complex disc‐gel patterns found with electrophoresis on acrylamide using a phenol‐urea solvent system for solubilization. In comparable mitochondrial fractions, incorporation was highest in the interface material (half‐life 6–4 days), followed by insoluble proteins (half‐life 3–6 days), and lowest in the soluble (brain) fraction (half‐life 6–26 days).Considerable hydrolase activity was observed in crude fractions and in hypotonic myelin fractions, particularly acid and neutral proteinases, aminopeptidase, and monoacyl and dipeptidyl arylamidases. It appears that hydrolases associated with the sheath could be involved in turnover, but in most cases are not associated with the highly purified membranes prepared in sucrose and CsCl gradients. Purification resulted in an increased specific activity of an aminopeptidase hydrolysing Leu‐Gly‐Gly as the substrate, and of ribonucleoside‐2′ : 3′‐cyclic‐phosphate esterase. It is concluded that these two hydrolases are intrinsic components of the myelin sheath membranes.

Metabolism of insulin and glucagon. Breakdown of radioiodinated insulin and glucagon in rat liver cell fractions.

An enzyme catalyzing the reductive breakdown of insulin was isolated and purified from microsomes of rat liver. Its properties resemble strongly those of glutathione-insulin transhydrogenase (thiol-protein disulfide oxidoreductase) from bovine liver, human liver, bovine pancreas, and human kidney. The enzyme was separated from microsomes by deoxycholate and purified by gel filtration on Sephadex G-75 and subsequent chromatography on DEAE-Sephadex A-50. Disc electrophoreses showed that highly purified, fresh enzyme preparations consist of only two enzymatically active proteins, forming one main band and a faint band, without any further visible contaminants. The content of glutathione-insulin transhydrogenase in rat liver amounts to about 0.5–1% of total liver proteins as calculated from the purification factor. The molecular weight of the microsomal transhydrogenase determined by gel filtration on Sephadex G-75 is 50000 to 55000. Using disc electrophoresis in dodecylsulfate-containing gels molecular weights of 60000 and 121000 were determined for the main component and the second, slower-migrating band of the enzyme, respectively. The Michaelis-Menten constants for insulin and glutathione (in the presence of EDTA) are 31 μM (mol. wt 6000) and 1.43 mM, respectively. Maximum breakdown of 125I-labelled insulin was found at pH 7.3. It seems very probable that our transhydrogenase from rat liver microsomes is identical or very similar to the enzyme catalyzing the reactivation of “randomly-oxidized” ribonuclease (Anfinsen).

Horse spleen hemosiderin: I. Isolotion

A method is described for the isolation of hemosiderin granules from horse spleen; it is based on differential centrifugation in concentrated aqueous potassium iodide solutions. This method achieves a good yield of hemosiderin granules that are free of any visible contamination. Chemical analysis of some of the components of the granules is reported.

Direct Observation of Surface Contamination formed in Demountable Vacuum Systems

THE visible contamination of specimens examined in the electron microscope is the result of a reaction between the electron beam and matter adsorbed on the irradiated surface. This adsorbed material is known to consist of hydrocarbon molecules1, though it may also contain some water molecules; it exists on surfaces in all demountable vacuum systems. The layer is troublesome in many experiments and processes involving such systems, but evidence of its presence is only indirect and little is known about its thickness or composition. It is particularly noticeable in high-resolution shadow-casting for the electron microscope (unpublished work), since it limits the resolution by causing a fine background structure. In the course of an investigation of this structure, a method was found for studying the adsorbed layer directly, and also for estimating its thickness. It was found that the layer was visible in the electron microscope when viewed end-on and sandwiched between two carbon films (see Fig. 1). The procedure is carried out as follows.