Nucleotide analogue inhibitors of purine nucleoside phosphorylase

The diphosphate of the antiherpetic agent acyclovir [9-[(2-hydroxyethoxy)methyl]guanine] has been shown to inhibit purine nucleoside phosphorylase with unique potency (Tuttle, J. V., and Krenitsky, T. A. (1984) J. Biol. Chem. 259, 4065-4069). A major factor contributing to the superior inhibition by this diphosphate over the corresponding mono- and triphosphates is revealed here. Homologues of acyclovir mono- and diphosphate that extend the ethoxy moiety by one to four methylene groups were synthesized. These homologues were evaluated for their ability to inhibit human purine nucleoside phosphorylase. Within the diphosphate series, the Ki values increased progressively with increasing chain length. With the monophosphates, the Ki values reached a minimum with the homologue containing a pentoxy moiety. A plot of chain length versus Ki values for both mono- and diphosphates showed that both series had similar optimal distances between the aminal carbon and the terminal oxygen anion. Monophosphates with optimal positioning were somewhat less potent than diphosphates with similar positioning. Nevertheless, it was clear that a major factor in determining potency of inhibition was the distance of the terminal phosphate from the guanine moiety.     

Distribution and oxidation of malondialdehyde in mice

The in vivo metabolism of malondialdehyde (MDA) by male and female Swiss mice was investigated. Distribution of an i.p. dose of MDA is rapid and uniform throughout the body. Conversion of 14C-labeled MDA to CO2 is complete 4 hours after an i.p. dose of 5 mumol to 200 mumol with no signs of short term toxicity. The yields of CO2 from [1-14C]-beta-alanine, [3-14C]-beta-alanine, [1-14C]-sodium acetate, and [2-14C]-sodium acetate were also determined. Comparison of the yields of CO2 from this series of compounds suggests the intermediacy of malonic semialdehyde in the metabolism of MDA. High doses (600 mumol) of beta-alanine or acetate given prior to 14C-MDA reduced the yield of 14CO2. Ethanol and disulfiram were both inhibitors of MDA metabolism, indicating the involvement of aldehyde dehydrogenase in the oxidation of MDA. These data demonstrate the ability of animal tissues to rapidly remove exogenously administered MDA. They also have implications with respect to the possible pathological consequences of in vivo MDA generation.     

High-performance liquid chromatographic assay detects pentamidine metabolism by Fisher rat liver microsomes

Fisher rat liver microsomes metabolized the antimicrobial drug pentamidine to four new compounds detected by gradient elution reversed-phase high-performance liquid chromatography with variable wavelength detection. Coelution experiments with pentamidine metabolite standards determined the new peaks to be previously identified hydroxylated metabolites of pentamidine, with 1,5-bis(4′-amidinophenoxy)-3-pentanol and 1,5-di-(4′-amidinophenoxy)-2-pentanol formed in the greatest amount. The data contradict a previous report that Fisher rat liver homogenates do not metabolize pentamidine. Pentamidine and its known primary metabolites have almost identical absorption spectra; thus, pentamidine metabolism must be evaluated using gradient elution HPLC to resolve pentamidine from its metabolites. The current assay has now been used to demonstrate that Fisher and Sprague-Dawley rat, mouse, rabbit and human liver microsomes all metabolize pentamidine in vitro.     

The treatment of cancer patients with human lymphoblastoid interferon

Summary Highly purified human lymphoblastoid interferon (HLBI) derived from virus-stimulated Namalwa cells was administered by 6-h IV infusion or IM injection to 40 patients with a variety of disseminated malignancies refractory to standard therapy. Each patient received doses escalating from 0.1 to 50×10⁶ U for up to 5 weeks. Extensive monitoring for clinical effect, toxicity, and pharmacokinetics has revealed higher peak serum interferon levels and somewhat more pronounced systemic toxicity for the IV than for the IM route of administration. Objective evidence of tumor regression was observed in two patients receiving HLBI IV.     

Microbial Sulfate Reduction and Its Potential Utility as an Acid Mine Water Pollution Abatement Procedure

The presence of high concentrations of sulfate, iron, and hydrogen (acid) ions in drainage from coal mines and other areas containing waste pyritic materials is a serious water pollution problem. Sulfate can be removed from solution by microbial reduction to sulfide and subsequent precipitation as FeS. A mixed culture of microorganisms degraded wood dust cellulose, and the degradation products served as carbon and energy sources for sulfate-reducing bacteria. Metabolism of carbon compounds resulted in a net pH increase in the system. Oxidation-reduction potential (Eh) and temperature and carbon supplements were studied in an effort to accelerate the sulfate reduction process, with the ultimate objective of utilizing the process as a pollution abatement procedure.     

The role of prey-generated sounds,vision, and echolocation in prey localization by the African batCardioderma cor (Megadermatidae)

Summary Cardioderma cor responded with head movements and flight toward speakers broadcasting calls of frogs and crickets which contained only sonic frequencies. Unlike the frog-eating bat,Trachops cirrhosus, they did not make contact with the speakers. Prey movements that generated sonic and ultrasonic sounds were both sufficient and necessary for the bats to localize and capture prey. Prey dragged across a glass sheet with a thin layer of water did not generate sounds and bats did not attempt to capture these prey, even with the availability of visual and echolocation cues. There was no evidence for the use of visual cues while hunting; bats did not localize prey more readily in light than darkness. Prey were presented such that their movements initially generated sounds, but then the prey moved onto the water layer of the glass sheet and sounds were eliminated. The bats emitted echolocation signals while hunting in this situation; however, the information from these signals was not utilized. The bats landed at the site that prey last made sound. These results demonstrate the importance of passive hearing for prey localization in this bat, and further suggest that when preygenerated sounds and echolocation signals offer conflicting information the bat's behavior is guided by the former.