Conformation of azidothymidine: an anti-AIDS drug

The nucleoside antibiotic, 3′-azido-3′-deoxythymidine, or simply, azidothymidine has shown great promise in inhibiting the human immuno deficiency virus and in reducing mortality among AIDS patients. Conformational properties of azidothymidine have been investigated by quantum-mechanical PCILO method and compared with those of the parent nucleoside, thymidine. The results indicate great similarity between them and this similarity is remarkably striking in the situations that prevail in aqueous solution. This result has important biological significance in explaining the drug action of azidothymidine.     

Acute effect of substance P in immunologic vasculitis in the rat colon

Substance P has been implicated as a neuronal mediator of inflammation in various inflammatory conditions. However, the exact role played by substance P in inflammatory bowel diseases or in experimental colonic vasculitis has not been clearly understood. In this study, we examined the effect of close superior mesenteric artery injection of substance P under prevailing inflammatory conditions induced by intravenous human albumin antialbumin immune complex followed by intracolonic perfusion of 2.5% formaldehyde in rats or intracolonic perfusion of 5% alcohol alone. The immune complex- and formaldehyde-treated rats showed severe microvascular changes such as microvascular plugging by red blood cells, endothelial breakage and extravasation of plasma proteins and red blood cells. The bolus injection of 10⁻⁸ M substance P reduced extravasation of Evans blue dye by 50% and the tissue wet to dry ratio by 20% in immune complex- and formaldehyde-perfused rats. Myeloperoxidase activity was not changed. Substance P also significantly inhibited (44%) the extravasation in alcohol-perfused rats. Pretreatment of immune complex- and formaldehyde-treated rats with substance P antagonist reversed the effect of substance P. These findings suggest that the most immediate effect of substance P may be vasodilation and clearing of vascular plugs induced by immune complex and formaldehyde. This effect of substance P differs from its chronic effect, which causes vasodilation and extravasation.     

Vascular organization of the head and respiratory organs of the air-breathing catfish,Heteropneustes fossilis

Light and scanning electron microscopy of vascular replicas from the facultative air-breathing fish Heteropneustes fossilis show modifications in the macrocirculation of the respiratory organs and systemic circulation, whereas, gill microcirculation is similar to that found in typical water-breathing fish. Three and sometimes four ventral aortae arise directly from the bulbus. The most ventral vessel supplies the first pair of arches. Dorsal to this another aorta supplies the second gill arches, and a third, dorsal to, and larger than the other two, supplies the third and fourth arches and the air sacs. Occasionally a small vessel that may be the remnant of a primitive aortic arch arises from the first ventral aorta and proceeds directly to the mandibular region without perfusing gill tissue. The air sac is perfused by a large-diameter extension of the afferent branchial artery of the fourth gill arch and its circulation is in parallel with the gill arches. Blood drains from the air sac into the fourth arch epibranchial artery. A number of arteries also provide direct communication between the efferent air sac artery and the dorsal aorta. All four gill arches are well developed and contain respiratory (lamellar) and nonrespiratory (interlamellar and nutrient) networks common to gills of water-breathing fish. Air sac lamellae are reduced in size. The outer 30% of the air sac lamellar sinusoids are organized into thoroughfare channels; the remaining vasculature, normally embedded in the air sac parenchyma, is discontinuous. A gill-type interlamellar vasculature is lacking in the air sac circulation. Despite the elaborate development of the ventral aortae, there is little other anatomical evidence to suggest that gill and air sac outflow are separated and that dorsal aortic oxygen tensions are maintained when the gills are in a hypoxic environment. Physiological adjustments to hypoxic water conditions probably include temporal regulation of gill and air sac perfusion to be effective, if indeed they are so.     

The Role of Angiopoietins as Potential Therapeutic Targets in Renal Cell Carcinoma

Angiopoietin 2 (Ang2) is a secreted glycoprotein upregulated at sites of angiogenesis and has been implicated in cancer neovascularization. Recent studies have suggested efficacy of combined Ang and vascular endothelial growth factor receptor (VEGFR) inhibition for patients with metastatic renal cell carcinoma (mRCC). We measured Ang2 expression in human tissue and plasma, and tested the effect of dual Ang1/2 (trebananib; AMG386) or Ang2 alone (L1-7) inhibition with VEGFR inhibition on murine RCC growth and blood flow. Ang2 levels were higher in human tumors than normal tissues with RCC ranking highest for Ang2 expression across all tumor types tested. Plasma Ang2 was significantly higher in patients with mRCC compared to controls or patients with stage I disease. Plasma Ang2 decreased with sunitinib treatment and increased at time of disease progression. In the RCC mouse, dual Ang1/2 and Ang2 inhibition improved the activity of sunitinib. Combined Ang1/2 and VEGFR inhibition prevented the resumption of blood flow associated with sunitinib resistance. Thus, Ang2 inhibition, independent of Ang1 inhibition, improves the activity of sunitinib and plasma Ang2 increases in the setting of progression on sunitinib possibly contributing to resistance. Further, arterial spin-labeled perfusion magnetic resonance imaging might be a non-invasive marker of the antiangiogenic activity of Ang inhibitors.     

An experimental model of Actinobacillus suis infection in mice

Actinobacillus suis is an opportunistic pathogen of high health status swine and is associated with fatal septicemia, especially in neonatal pigs. A practical model of A. suis is unavailable currently. However, some evidence suggests that A. suis can infect nonporcine species. We therefore hypothesized that a mouse model of A. suis infection might be possible. To test this idea, we challenged CD1 mice with 3 strains of A. suis (2 porcine [SO4 and H91-0380] and 1 feline [96-2247]) by intranasal and intraperitoneal routes. We also evaluated the effects of coadministration of hemoglobin and immunosuppression by dexamethasone on the susceptibility of mice to A. suis infection. The feline and H91-0380 porcine strains induced clinical signs of acute disease and necrotizing pneumonia in mice similar to those seen in pigs. Although few bacteria were recovered, dissemination of A. suis was widespread. Generally, mice infected with the feline A. suis isolate had more severe clinical signs and higher bacterial titers than did mice infected with either of the porcine strains. Pretreatment of the mice with dexamethasone or addition of 2% porcine hemoglobin to the challenge inoculum appeared to hasten the onset of clinical signs by the porcine strains but had no significant effect on moribundity. These experiments demonstrate that mice can be infected with A. suis and subsequently develop pneumonia and bacteremia comparable to that seen in pigs, suggesting that mice may be used as a model for studying infection in swine.     

Proteolytic Cleavage of a Spectrin-Related Protein by Calcium-Dependent Protease in Neurospora crassa

To investigate the functional significance of a cytoskeletal spectrin-like protein, we studied its localization pattern in Neurospora crassa and sought the answer to whether it is a substrate for another apically localized protein, the calcium-dependent protease (CDP II). Immunoblots of crude extracts from exponentially growing mycelia, separated by one- and two-dimensional sodium dodecyl sulfate–polyacrylamide gel electrophoresis using antichicken α/β-spectrin antibodies, revealed a single band of approximately relative mass (Mr) 100 kDa with an isoeletric point (pI) in the range of 6.5 to 7.0. Despite rigorous efforts, we could not confirm the presence of an Mr 240- to 220-kDa spectrin-like protein in N. crassa. The immunofluorescence- and immunogold-labeling Mr 100-kDa protein showed its predominance along the plasma membrane of the conidia during the swelling phase of germination. In contrast, in the germ tubes and the growing hyphae, the localization was polarized and concentrated mainly in the apical region. The in vitro proteolysis experiments showed that indeed this protein is a preferred substrate of CDP II which is, as mentioned previously, also localized in the apical regions of the hyphae. These results indicate a putative functional relationship between these two proteins (spectrin-like protein and CDP II) in the dynamics of tip growth.     

4-(1,1-Dioxo-1,4-dihydro-1lambda6-benzo[1,4]thiazin-3-yl)-5-hydroxy-2H-pyridazin-3-ones as potent inhibitors of HCV NS5B polymerase

4-(1,1-Dioxo-1,4-dihydro-1lambda(6)-benzo[1,4]thiazin-3-yl)-5-hydroxy-2H-pyridazin-3-one analogs were discovered as a novel class of inhibitors of HCV NS5B polymerase. Structure-based design led to the identification of compound 3a that displayed potent inhibitory activities in biochemical and replicon assays (1b IC(50)<10 nM; 1b EC(50)=1.1 nM) as well as good stability toward human liver microsomes (HLM t(1/2)>60 min).