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The engineer will be able to design a successful screened enclosure using careful selection of materials, gaskets and, if necessary, screened optical windows. Many of the techniques covered in this series of articles can be employed during the research and development stage to arrive at a cost-effective solution that offers the required mechanical, aesthetical, environmental and electrical properties.
Nanosized A2SnO4 (A = Ca, Sr, Ba) : 1% Eu with diameters ranging from 50 to 100 nm were synthesized by complex sol-gel methods. The structures and spectral properties of A2SnO4 (A = Ca, Sr, Ba) : Eu were studied by using X-ray powder diffraction (XRD) and luminescence spectra. The experimental results show that Ca2SnO4 : 1% Eu exhibits bright red emission at about 615 nm under UV excitation, which makes it a possible good candidate for FED application. However Sr2SnO4 : 1% Eu and Ba2SnO4 : 1% Eu exhibit orange emission at about 590 nm because in these hosts Eu3+ ions occupy the symmetric sites.
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To determine whether Ca2+ participates in the augmentative action of SnCl2 on the transmitter release, we have investigated interactions between SnCl2 and Cd2+, verapamil, or low Ca2+ on endplate potentials (e.p.p.) and have compared the effect of SnCl2 with that of Mg2+ on miniature endplate potentials (m.e.p.p.). SnCl2 increased the e.p.p. amplitude dose-dependently. Cd2+, verapamil and low Ca2+ shifted the dose-response relationship between SnCl2 and the e.p.p. downwards. In contrast to Mg2+, SnCl2 increased the m.e.p.p. frequency with raised K+ concentration in the medium. These results suggest that Ca2+ participates in the SnCl2-induced facilitation of the transmitter release and that SnCl2 enhances the Ca2+ entry into the nerve terminals.
Indices reflecting the functional state of the central nervous system, peripheral blood, enzymes and gonads were used in accordance with the toxico-dynamics of substances. Besides, body mass, behavior of animals, pathomorphological and histochemical indices were studied. 5 concentrations of tin chloride were studied: 400, 80, 15, 3 and 0.5 mg/m3. On the basis of an acute experiment (6-1440 h) it has been established, that the concentration-time relationship according to a number of biochemical and physiological parameters on the graph was expressed by direct lines on the double log scale with angles to abscissa from 124.9 degrees (according to blood transaminase activity reduction) up to 138.2 degrees, which allowed to determine the class of danger, safety and cumulation coefficients, threshold and no-effect concentrations of tin chloride under inhalational exposure to it. The lowest no-effect concentration 0.05 mg/m3 is recommended as an average 24-hour MAC and approved by the USSR Public Health Ministry.
Effects of stannous chloride (SnCl2, 30-100 microM) on presynaptic currents recorded from frog neuromuscular junctions were investigated to confirm that increased calcium entry is involved in SnCl2-induced facilitation of the evoked transmitter release. After the potassium channel was blocked by tetraethylammonium (0.1 mM) and 3,4-diaminopyridine (10 microM), SnCl2 (0.1 mM) augmented the prolonged positive deflection of the presynaptic action potential ascribable to calcium inward current, which was thereafter suppressed by the addition of cadmium (0.1 mM). These results suggest that SnCl2 enhances the calcium inward current at the motor nerve terminals.
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Lymphoscintigraphy, using technetium-99m-labeled sulphur microcolloid, was employed to study the flow and transport of lymph in the lower extremities of 39 consecutive patients in whom lymphedema of one or both legs was suspected clinically. Time-activity curves of four segments of each leg were evaluated for lymph capacity, flow and soft-tissue uptake, and compared with the results from film scintigraphy. Curve analysis provided quantitative evaluation of the extent of hypoplasia or aplasia in primary lymphedema and of lymphatic obstruction in secondary lymphedema, and is particularly suited to assess the involvement of lymphatics in chronic venous disease. Film scintigraphy, on the other hand, is preferable in cases in which the pattern of activity distribution in the affected extremity is diagnostic, such as in dermal back flow, traumatic lymphocele, or megalymphatics. Venography is most informative in cases of suspected underlying venous disease, but the role of lymphangiography, which shows only part of the lymphatic system and requires incision of the edematous tissues, is considered questionable.
Reduction of disulfide bonds to sulfhydryl groups for direct radiolabeling of antibodies for immunoscintigraphic and therapeutic applications continues to be of considerable interest. Sensitive spectrophotometric methods have been evaluated that will enable investigators to determine submicrogram quantities of cysteine units produced, for the assurance of controlled reduction. One method, which generates a cysteine-ninhydrin complex (520 nm), has a molar extinction coefficient of 30 250 and can determine 0.04 micrograms/ml cysteine units with an absorbance of 0.01. The method has been applied to determine the quantity of cysteine groups produced by the reduction of an immunoglobin G antibody with five different reducing agents in normal to five times the previously determined optimal molar ratios. The quantities of cysteine units produced from the controlled reduction from 240 micrograms immunoglobin G ranged from 0.073 +/- 0.01 to 1.07 +/- 0.04 micrograms, which were merely 0.54 +/- 0.08% to 7.9 +/- 0.28% of the total available disulfide groups in the protein.
The study of the labelling of planaria with 99mTc shows that the incorporation of radioactivity in this platyhelminth increases with an increase in SnCl2 concentration from 0.13 to 1.3 microM, reaching a plateau in the range of 1.3-130 microM then decreasing with 1300 microM. At concentrations of 1.3 and 13 microM SnCl2, a stronger binding of 99mTc was obtained. The biological viability of the labelled planaria was not altered when the described methodology was used. The advantage of this new labelling technique is that it is possible to obtain a platyhelminth preparation labelled with a radionuclide that is very cheap, is easily available and is a gamma emitter with a photon energy of 140 keV.
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Stannous fluoride colloid (SFC) kits for instant radiolabeling with 99mTc were prepared and evaluated for suitability as a leukocyte radiolabeling agent. Technetium-99m labeling for kits stored at -15 degrees C for up to 3 mo was greater than 95% as determined by instant thin layer chromatography while colloid particles of 1-3 microns were measured by electron microscope for these preparations. Canine leukocyte preparations labeled with [99mTc]SFC and characterized by triple density gradients of metrizamide in plasma demonstrated an 83% leukocyte association. Analysis of labeled cell preparation for up to 3 hr demonstrated label stability. Labeled leukocytes, when readministered in normal dogs, demonstrated bi-exponential blood clearance with uptake and subsequent clearance from lung. There was increasing uptake of labeled leukocytes by the liver until steady state was achieved. Furthermore, when whole blood samples were analyzed by the triple density gradient method, an increasing monocyte-to-granulocyte ratio was observed to occur with time. By 3 hr 95% of the whole blood activity was associated with the leukocyte fraction. Dogs in which a 24-hr sterile abscess was created demonstrated elevated blood-pool activity as compared to control with localization of the labeled cells at inflammatory sites within 3 hr following cell readministration.
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Present study was conducted to elucidate the mechanism of twitch augmentation by stannous ion. Stannous ion increased the amplitude of the endplate potential and moreover, generated repetitive firing of the muscle fiber. These findings suggest that the twitch augmentation by stannous ion may be due not only to recruitment of the muscle fibers but also to a brief tetanic contraction of the individual fibers.
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