Flexibility as a Strategy in Nucleoside Antiviral Drug Design.

As far back as Melville Wolfrom's acyclic sugar synthesis in the 1960's, synthesis of flexible nucleoside analogues have been an area of interest. This concept, however, went against years of enzyme-substrate binding theory. Hence, acyclic methodology in antiviral drug design did not take off until the discovery and subsequent FDA approval of such analogues as Acyclovir and Tenofovir. More recently, the observation that flexible nucleosides could overcome drug resistance spawned a renewed interest in the field of nucleoside drug design. The next generation of flexible nucleosides shifted the focus from the sugar moiety to the nucleobase. With analogues such as Seley-Radtke "fleximers", and Herdewijn's C5 substituted 2'-deoxyuridines, the area of base flexibility has seen great expansion. More recently, the marriage of these methodologies with acyclic sugars has resulted in a series of acyclic flex-base nucleosides with a wide range of antiviral properties, including some of the first to exhibit anti-coronavirus activity. Various flexible nucleosides and their corresponding nucleobases will be compared in this review.

Apocynum venetum leaf extract, an antihypertensive herb, inhibits rat aortic contraction induced by angiotensin II: a nitric oxide and superoxide connection.

ETHNOPHARMACOLOGICAL RELEVANCE: The leaves extract of Apocynum venetum (AVLE), also known as "luobuma", have long been used in traditional Chinese medicine to treat hypertension and depression in parts of China and it has been shown to possess anti-oxidant and anti-lipid peroxidation effects. AVLE (10 µg/ml) has been reported to have a long-lasting endothelium-dependent relaxant effect and this effect has been proposed to be due to its nitric oxide(NO)-releasing and superoxide anion(SOA)-scavenging properties. AIM OF THE STUDY: The present study seeks to evaluate the differential actions of AVLE extract between Ang II- and PE-induced vasoconstriction and the involvement of superoxide anions. MATERIALS AND METHODS: Single dose of Ang II (100 nM and 1 nM)- or PE (0.1 µM)-induced contraction were assessed in both endothelium-intact and -denuded aortic rings after pre-incubation of AVLE (10 µg/ml) for 15 min. The experiment was repeated in either the presence of NO synthase inhibitor, L-NAME (300 µM) or selective AT(1) receptor inhibitor, losartan (0.1 nM), or superoxide scavenger, tiron (1 mM) or a combination of L-NAME and AVLE. Superoxide production was measured by using enhanced-chemiluminescence assay. RESULTS: We have demonstrated that AVLE (10 µg/ml) effectively suppressed the Ang II-induced contraction (100 nM and 1 nM) of both endothelium-intact and -denuded rat aortic rings. In endothelium-intact rings, L-NAME, reversed AVLE-induced inhibition of Ang II-contraction. PE-induced contraction was significantly inhibited by AVLE in endothelium-intact rings, but not in endothelium-denuded rings. The inhibition by AVLE of PE-induced contraction was totally abolished in the presence of L-NAME. Ang II-induced SOA production concentration dependently with the optimal effect seen at 100 nM of Ang II, and AVLE (0.3, 1, 10 µg/ml) reduced this effect. SOA production in Ang II-stimulated rings was significantly higher than unstimulated control rings, while PE did not stimulate SOA production at all. SOA formation in the presence of Ang II was also inhibited in the presence of SOD (superoxide scavenger), DPI (NADPH inhibitor) and losartan (specific AT(1) receptor antagonist). CONCLUSION: These results collectively suggest that the ability of AVLE in inhibiting Ang II-induced contraction via its SOA scavenging properties and nitric oxide releasing effect may account for its usage as an antihypertensive treatment in traditional folk medicine.

Alveolar bone height of primary and first permanent molars in healthy seven- to nine-year-old children.

The purpose of the study was to establish baseline values of the alveolar bone height of the primary molars and first permanent molars in sample of healthy U.S. seven- to nine-year-old children. Direct measurements of the distance from the cementoenamel junction (CEJ) to the alveolar crest (AC) on 223 pairs of bitewing radiographs from 223 subjects were made using a digimatic caliper under standardized conditions. The distance from the CEJ to the AC had medians from 0.58 mm to 1.39 mm (range 0.0 to 4.44 mm) for the primary molars and from 0.00 mm to 0.64 mm (range -1.35 to 2.15 mm) for the mesial aspect of the permanent molars. There were no statistically significant differences in the distance from CEJ to AC between teeth on the right and left sides of the mouth. The distances from CEJ to AC were always greater in the maxilla than in the mandible for similar primary molar sites, but only true for the mesial aspect of the permanent first molar at age nine. As a tooth is positioned more anteriorly in the mouth, the distance from CEJ to AC was greater. On the whole, males had greater distances than females and eight-year-olds had larger distances than seven- or nine-year-olds. Differences were observed in the measured distances for the different age and sex-groups and may be attributable to variations in eruption and exfoliation patterns. The distance was significantly greater in areas of interproximal restorations and open contacts, and there was a tendency for the distances to be greater in areas of interproximal caries.

Rapid primary microwave-aldehyde and microwave-osmium fixation: improved detection of rat parotid acinar cell secretory granule alpha-amylase using a post-embedding immunogold ultrastructural morphometric analysis.

Studies of methods for improved fixation are becoming increasingly important in the field of quantitative immunocytochemistry. We used microwave (MW)-assisted chemical fixation to show improved retention of salivary gland acinar cell secretory granule alpha-amylase detected by a quantitative immunogold method. Blocks (4-mm3) of rat parotid gland were fixed by the following methods: (a) MW irradiation in an aldehyde fixative (AF) for 6 sec; (b) immersion in AF for 1.5 hr; (c) MW irradiation in osmium tetroxide (OT) for 9 sec; (d) immersion in OT for 1.5 hr; or (e) Sequential MW AF, 10 sec, MW OT rapid treatment (SMAORT), 10 sec. Specimens were processed routinely for transmission electron microscopy. Thin sections of Epon-embedded tissues were exposed first to rabbit IgG anti-human salivary alpha-amylase and second to gold-conjugated goat anti-rabbit IgG. Granule area was obtained by a point counting method. Labeling density was calculated as the number of gold particles/micron 2 +/- SD. Specimens fixed in seconds by MW-AF, MW-OT, or SMAORT showed ultrastructural preservation similar to immersion fixation in AF or OT for 1.5 hr. Immunogold labeling density of granule alpha-amylase was highest for SMAORT (874 microns 2) compared to MW-AF (295 microns 2), MW-OT (248 microns 2), routine sequential immersion in AF and OT (229 microns 2), or immersion in OT (no aldehyde) (190 microns 2). This study establishes the improved retention of salivary gland acinar cell secretory granule alpha-amylase and markedly enhanced fixation speed for ultrastructural studies made possible by MW-chemical fixation protocols that use aldehydes and osmium.