Trehalose Increases Freeze-Thaw Damage in Liposomes Containing Chloroplast Glycolipids

Chloroplast thylakoids contain three classes of glycolipids, monogalactosyldiacylglycerol (MGDG), digalactosyldiacylglycerol (DGDG), and sulfoquinovosyldiacylglycerol (SQDG). We have investigated the stability of large unilamellar vesicles made from egg phosphatidylcholine (EPC) and different chloroplast glycolipids during freezing to -18 degreesC, as a function of the presence of three sugars: glucose, sucrose, or trehalose. Contrary to the situation in thylakoids, where cryoprotection increases from glucose < sucrose < trehalose, liposomes containing 50% DGDG showed the opposite behavior. In fact, carboxyfluorescein leakage increased over the control values (freezing in the absence of sugar) in the presence of trehalose. This effect was not seen in vesicles made from pure EPC, or a mixture of EPC and MGDG, or EPC and SQDG. Liposomes made from mixtures of all three glycolipids, however, showed even more leakage in the presence of trehalose than liposomes containing only DGDG and EPC. Copyright 1998 Academic Press.     

Anti-pneumocystis activity of bis-amidoximes and bis-o-alkylamidoximes prodrugs

We report the synthesis of 2,5-bis-[4-amidinophenyl]furan bis-amidoxime(2), the corresponding bis-O-methylamidoxime(3) and the corresponding bis-O-ethylamidoxime(4) and their evaluation as prodrugs against Pneumocystis carinii pneumonia.     

Lack of geographic variation in anonymous nuclear polymorphisms in the American oyster, Crassostrea virginica

Comparing geographic variation of noncoding nuclear DNA polymorphisms, which presumably are neutral to natural selection, with geographic variation of allozymes is potentially a good way to detect the effects of selection on allozyme polymorphisms. A previous study of four anonymous nuclear markers in the American oyster, Crassostrea virginica, found dramatic differences in allele frequency between the Gulf of Mexico and the Atlantic Ocean. In contrast, 14 allozyme polymorphisms were fairly uniform in frequency between the two areas. This led to the conclusion that all of the allozyme polymorphisms were kept uniform in frequency by balancing selection. To test the robustness of this pattern, six additional anonymous nuclear DNA polymorphisms were surveyed in oysters from Panacea, Fla, and Charleston, S.C. on the Gulf and Atlantic coasts, respectively. Unlike the previously studied DNA markers, the six DNA polymorphisms examined here show geographic variation that is not significantly greater than that of allozymes. The reason for the discrepancy between the two sets of DNA polymorphisms is unclear.      

INTERCONNECTED REPRODUCTIVE AND VEGETATIVE REMAINS OF POPULUS (SALICACEAE) FROM THE MIDDLE EOCENE GREEN RIVER FORMATION,NORTHEASTERN UTAH

A new specimen from the Middle Eocene Evacuation Creek Member of the Green River Formation in northeastern Utah shows a twig with several leaves of Populus wilmattae Cockrell and a fruiting raceme attached. This specimen establishes for the first time the type of fruits borne by P. wilmattae and provides additional characters with which to assess its taxonomic and evolutionary status. An associated seed shows attached placental hairs like those of extant species of Populus. The Green River fossil differs from extant Populus species in having basically palmate leaf venation and in bearing its fruiting axis on a young twig. In other aspects, the fossil species is remarkably similar to the extant species Populus mexicana.     

The methylation of transfer ribonucleic acid during regeneration of the liver

Transfer ribonucleic acid¹ is methylated after the molecule is synthesized; at least eight enzymes are involved in the transfer of methyl groups (derived from methionine). The time courses of methylation and synthesis of tRNA during rat liver regeneration have been compared in an in vivo radioisotopic study, using 6-orotic acid-¹⁴C and ³H-methyl-L-methionine as precursors in double label pulses. Liver regeneration is a synchronized system in which biochemical events of the cell cycle are separable. Transfer RNA methylation increase precedes by several hours tRNA synthesis during regeneration, although the curves overlap. A ratio of the relative rate of methylation to the relative rate of synthesis has been made; that curve positively correlates with the rise and fall of protein synthesis during regeneration. It is clear that methylation and synthesis of tRNA are only weakly coupled; changing methyl content of the tRNA "pool" resulting from differential tRNA methylase and polymerase activities may regulate the rate of protein synthesis in the cell cycle at the translational level. The "pool sizes" of uridine monophosphate (UMP) and S-adenosylmethionine (SAM) were measured indirectly; UMP and SAM were isolated from perchloric acid supernatants and their specific activities were computed. Differential changes in radioactivity available to tRNA methylases and polymerases are not a source of artifact. That is, the control of both the synthesis and methylation of tRNA is at the enzyme level in vivo, rather than at some enzymatic step prior to those enzymatic reactions.     

Effect of ingestion of unsaturated fat on lipolytic activity of rat tissues

Homogenates of some rat tissues, incubated in Tris-maleate buffer containing bovine serum albumin, olive oil emulsion, heparin, and serum, liberated free fatty acids. The total lipolytic activity in tissues of rats fed a low fat, 20% lard, or 20% corn oil diet for 6 wk was measured. Similar activities were found in all the livers, but there was a significant increase in the total lipolytic activity of the mucosa, epididymal fat, and mesenteric tissues after ingestion of an unsaturated fat diet as compared with that containing a more saturated fat. From measurements of the lipolytic activity in the presence of 1 M NaCl or 0.2 M NaF and in the absence and presence of heparin and serum, the conclusion is drawn that more lipoprotein lipase was present in adipose tissue of rats on unsaturated fat diets. An increase in available lipoprotein lipase after unsaturated fat diets may aid in clearing lipids from the blood of these rats and thus in producing the lower blood lipid levels obtained.     

Two new fossil matoniaceous stem genera from Tasmania, Australia

Two new genera, Tasmanopteris and Heweria, from Tasmania are the first definite permineralized rhizomes assignable to the Matoniaceae. Tasmanopteris richmondii sp. nov., of mide-Mesozoic age, is from the Lune River site in southwestern Tasmania and is composed of four or more annular solenostelos separated by cortices with an inner mesarch xylem ring and outer exarch xylem rings. Secretory canals occur in the cortices between the protoxylem clusters of its outer xylem rings. The specimen of Heweria kempii sp. nov., which is very similar to extant Matonia, was collected from a Lower Tertiary conglomerate in central Tasmania but was reworked from older sediments. Anatomically, the rhizomes of Heweria consist of 3–6 annular solenosteles with the inner and middle xylem rings being mesarch, whereas the outer ring is exarch. Roots arise opposite the protoxylem clusters of the outermost ring. Epidermal hairs on the stems of this genus are like those of living Matonia in being attenuate, uniseriate, and multicellular.

Associated venation pattern of partially preserved leaves, isolated sporangia, annuli, and spores in this specimen provide additional support for the relationships of this fossil to modern Matonia.     

A novel tropically stable oral amphotericin B formulation (iCo-010) exhibits efficacy against visceral Leishmaniasis in a murine model

Purpose

To develop an oral formulation of amphotericin B (AmB) that is stable at the temperatures of WHO Climatic Zones 3 and 4 (30–43°C) and to evaluate its efficacy in a murine model of visceral leishmaniasis (VL).

Methods

The stability testing of four novel oral lipid AmB formulations composed of mono- and di-glycerides and pegylated esters (iCo-010 to iCo-013) was performed over 60 d and analyzed by HPLC-UV. In addition, the four formulations were incubated 4 h in fasted-state simulated intestinal fluid. AmB concentration was measured spectrophotometrically and emulsion droplet diameter was assessed by dynamic light scattering. Antileishmanial activity of iCo-010 was evaluated at increasing oral doses (2.5 to 10 mg/kg) in a murine model of VL.

Results

AmB stability in the lipid formulation (iCo-010) was >75% over 60 days. After 4 h in fasted-state simulated intestinal fluid, AmB concentration was >95%. iCo-010 demonstrated significant efficacy when orally administered to VL-infected mice bid for five days (inhibition of 99%, 98%, and 83% at 10, 5 and 2.5 mg/kg compared to the vehicle control). In addition, the qd dose of 20 mg/kg provided 96% inhibition compared to the vehicle control.

Conclusions

The oral AmB formulation iCo-010 is stable at the temperatures of WHO Climatic Zones 3 and 4 (30–43°C). iCo-010 showed excellent antileishmanial activity at both 10 mg/kg po bid for 5 days (<99% reduction in parasitic infection) and 20 mg/kg po qd for 5 days (95% inhibition when compared to control).