Cross-sections of thin film polymeric membranes, including reverse osmosis (RO), ultrafiltration (UF), and hollow fiber microfiltration (MF) membranes, are frequently used for both material analysis and for failure and fouling investigation. However, many techniques currently used to prepare cross-sections are far from ideal and result in distortion at cut surfaces. A modified freeze fracture method (Cryo-snap), where the specimen is embedded in ice before cleaving, was developed to minimize the stresses put on the sample during fracturing, thereby reducing the distortion to the cross-section and increasing the resulting detailed resolution. This method was compared to two commonly used sectioning methods, razor sectioning, and direct freeze fracturing. The Cryo-snap method rapidly yielded cross-sections with fewer artifacts than the traditional methods and the sample distortion was extremely low. The method is superior for membrane applications.
The purpose of this study was to determine the role of endogenous opioid peptides in the differentiation of the neuroendocrine brain that leads to estradiol-dependent LH release in female but not in male rats. Newborn intact or gonadectomized rats were given an opiate antagonist, naltrexone, with or without an opiate agonist, morphine, or saline alone during the critical period of the sexual differentiation of the brain (days 1–10). These animals were weaned on day 21 and injected with estradiol benzoate (EB) in oil or oil alone twice, 48 h apart, and the action of EB on plasma and pituitary levels of LH was studied. The release of LH during the prepubertal period was increased following EB treatment both in intact females and gonadectomized males and females, but not in intact male rats. Naltrexone treatment during the neonatal period prevented the EB-induced LH release in both intact and gonadectomized rats. Morphine blocked the inhibitory effect of naltrexone on LH release. Naltrexone treatment did not directly affect pituitary LH storage, but prevented EB-induced depletion of pituitary LH pools; morphine blocked this action of naltrexone. Hence, the inhibitory effect of naltrexone on LH release appeared to result from an alteration of the central mechanism responsible for EB-induced LH secretion. These results suggest a possible involvement of endogenous opioid peptides in the neuroendocrine brain differentiation that results in LH release after EB treatment during the prepubertal period in rats.
Navicula mutica (Kütz.) var. mutica was isolated from the air, cloned on agar, cultured in soil‐water bottle, and studied with transmission and scanning electron micros‐ropy. The frustules were lanceolate to ovoid with rounded apices, with the apical axis 8.5 ± 3.2 μ and the trans‐apical and the transapical axis 3.6 ± 0.6 μm. Striae were composed of two or three puncta, and the mantle bore a single row of puncta aligned with the striae. The ends of the raphe turned away from an isolated punctual in the central area of the valve. The mantle puncta and one or two of the valve‐face puncta in each stria opened into a series of transapical grooves in the interior of the valve, the grooves contributing to the appearance of striae in the light microscope. The interior of the mantle also possessed a pair of longitudinal grooves, discontinuous at the apices of the valves. An undulate advalvar margin of the valvocopula likely articulates along the interior longitudinal groove of the mantle. The projections of the undulate margin are perhaps positioned between the transapical grooves and along the longitudinal groove between the dentiform structures formed by the intersection of the double‐grooved system. The girdle bands each had two (occasionally three) rows of pores. The pleurae margins were straight and not undulate.
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