Synthesis and antiviral and antimicrobial activity of certain 1-beta-D-ribofuranosyl-4,5-disubstituted imidazoles.

Starting with AICA ribonucleoside the following nucleosides were prepared. Methyl 5-amino-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)imidazole-4-carboxylate (5) was converted into methyl 5-chloro-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)imidazole-4-carboxylate (6) via diazotization in the presence of cuprous chloride. Similarly, 5-amino-1-(2,3,5-tri-O-acetyl-beta-D-ribofuanosyl)imidazole-4-carbonitrile (9) was converted into 5-chloro-, 5-bromo-, and 5-iodo-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)imidazole-4-carbonitrile derivatives. These 5-halogenated imidazole nucleosides were treated with several nucleophiles such as ammonia, hydroxylamine, and hydrogen sulfide to provide, respectively, 5-haloimidazole-4-carboxamide, 5-haloimidazole-4-carboxamidoxime, and 5-haloimidazole-4-thiocarboxamide ribonucleosides. 5-Chloro- or 5-bromo-1-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)imidazole-4-carbonitrile was treated with potassium hydrosulfide to yield 5-mercapto-1-beta-D-ribofuranosylimidazole-4-thiocarboxamide (16). The catalytic reduction of 5-chloro- or 5-bromo-1-beta-D-ribofuranosylimidazole-4-carboxamidoxime provided 1-beta-D-ribofuranosylimidazole-4-carboxamidines as their hydrochloride and hydrobromide salts, respectively. These nucleosides were tested for in vitro antiviral, antifungal, and antibacterial activity. The 5-halo analogues of 1-beta-D-ribofuranosylimidazole-4-carboxamide showed significant antiviral activity whereas compound 16 was found inhibitory to fungi.     

Effect of pH changes on the binding of vitamin B12 by intrinsic factor

The binding of vitamin B(12) by human gastric juice has been found to be pH dependent. Maximum binding occurs between pH 6.5 and 10. Outside this pH range the vitamin B(12)-binding ability of human gastric juice decreases and at pH below 2 or above 12.2 this drops sharply to about 10 to 15% of the maximum. Three commercial hog intrinsic factors have been found to give a similar response to pH changes. The pH-dependent binder in human gastric juice has been shown to be intrinsic factor by the addition of intrinsic factor-blocking antibody. About 10% of vitamin B(12) bound by human gastric juice is not bound by intrinsic factor and is not pH dependent. The reduction in the vitamin B(12)-binding capacity of human gastric juice induced by an adverse pH is reversed by neutralization. The physiological and clinical significance of these observations is discussed and their relevance to various procedures in vitro noted.     

Synthesis and antiviral activity of certain thiazole C-nucleosides.

A general reaction of glycosyl cyanides with liquid hydrogen sulfide in the presence of 4-dimethylaminopyridine to provide the corresponding glycosylthiocarboxamides is described. These glycosylthiocarboxamides were utilized as the precursors for the synthesis of 2-D-ribofuranosylthiazole-4-carboxamide and 2-beta-D-ribofuranosylthiazole-5-carboxamide (23). The structural modification of 2-beta-D-ribofuranosylthiazole-4-carboxamide (12) into 2-(2,3,5-tri-O-acetyl-beta-D-ribofuranosyl)thiazole-4-carboxamide (15), 2-beta-D-ribofuranosylthiazole-4-thiocarboxamide (17), and 2-(5-deoxy-beta-D-ribofuranosyl)thiazole-4-carboxamide (19) is also described. These thiazole nucleosides were tested for in vitro activity against type 1 herpes virus, type 3 parainfluenza virus, and type 13 rhinovirus and an in vivo experiment was run against parainfluenza virus. They were also evaluated as potential inhibitors of purine nucleotide biosynthesis. It was shown that the compounds (12 and 15) which possessed the most significant antiviral activity were also active inhibitors (40-70%) of guanine nucleotide biosynthesis.     

Brain, skull, and cerebrospinal fluid volumes in adult posttraumatic stress disorder

Children and adolescents with maltreatment-related posttraumatic stress disorder (PTSD) exhibit smaller intracranial tissue volume than controls. Linear relationships have also been observed between intracranial tissue volume and the age of maltreatment onset. The authors explored associations among adult PTSD, early trauma, and cerebral volumes in 99 combat veterans. A bone-based estimate of cranial volume was developed to adjust for variation in body size. Posttraumatic stress disorder was not associated with smaller cerebral tissue volume, but rather with smaller cerebrospinal fluid (CSF) and cranial volumes. These findings co-occurred with expected effects of alcoholism and aging on cerebral tissue and CSF volumes. The results point to early developmental divergences between groups with and without PTSD following adult trauma.     

Induction of apoptosis by the ginsenoside Rh2 by internalization of lipid rafts and caveolae and inactivation of Akt

Background and purpose:

Lipid rafts and caveolae are membrane microdomains with important roles in cell survival signalling involving the Akt pathway. Cholesterol is important for the structure and function of these microdomains. The ginsenoside Rh2 exhibits anti-tumour activity. Because Rh2 is structurally similar to cholesterol, we investigated the possibility that Rh2 exerted its anti-tumour effect by modulating rafts and caveolae.

Experimental approach:

A431 cells (human epidermoid carcinoma cell line) were treated with Rh2 and the effects on cell apoptosis, raft localization and Akt activation measured. We also examined the effects of over-expression of Akt and active-Akt on Rh2-induced cell death.

Key results:

Rh2 induced apoptosis concentration- and time-dependently. Rh2 reduced the levels of rafts and caveolae in the plasma membrane and increased their internalization. Furthermore, Akt activity was decreased and consequently, Akt-dependent phosphorylation of Bad, a pro-survival protein, was decreased whereas the pro-apoptotic proteins, Bim and Bax, were increased upon Rh2 treatment. Unlike microdomain internalization induce by cholesterol depletion, Rh2-mediated internalization of rafts and caveolae was not reversed by cholesterol addition. Also, cholesterol addition did not restore Akt activation or rescue cells from Rh2-induced cell death. Rh2-induced cell death was attenuated in MDA-MB-231 cells over-expressing either wild-type or dominant-active Akt.

Conclusions and implications:

Rh2 induced internalization of rafts and caveolae, leading to Akt inactivation, and ultimately apoptosis. Because elevated levels of membrane rafts and caveolae, and Akt activation have been correlated with cancer development, internalization of these microdomains by Rh2 could potentially be used as an anti-cancer therapy.