Endovascular treatment of innominate artery stenosis in a bovine aortic arch--a case report.

Recent reports have established the feasibility and safety of percutaneous transluminal angioplasty and stent placement in the treatment of innominate artery occlusive disease. Although the long-term durability of these endovascular approaches has not been clearly established, they are particularly attractive in patients who are not considered good candidates for surgical reconstruction. The authors present a case involving a morbidly obese Hispanic woman who had undergone previous coronary artery bypass and complained of right visual symptoms, dizziness, and right upper extremity claudication. Because of her unusual bovine anatomy and the desire to avoid reoperating in her chest, a unique approach with a left subclavian-to-carotid bypass and innominate artery angioplasty and stenting was used.

Drosophila rab GDI mutants disrupt development but have normal Rab membrane extraction.

Rab GTPases are essential for vesicular transport. Rab GDP dissociation inhibitor (GDI) binds to GDP-bound rabs, removes rabs from acceptor membranes and delivers rabs to donor membranes. We isolated lethal GDI mutations in Drosophila and analyzed their developmental phenotypes. To learn how these mutations affect GDI structure, the crystal structure of Drosophila GDI was determined by molecular replacement to a resolution of 3.0 A. Two hypomorphic, missense mutations are located in domain II of GDI at highly conserved positions, but not in previously identified sequence conserved regions. The mutant GDIs were tested for ability to extract rabs from membranes and showed wild-type levels of rab membrane extraction. The two missense alleles showed intragenic complementation, indicating that domain II of GDI may have two separable functions. This study indicates that GDI function is essential for development of a complex, multicellular organism and that puparium formation and pole cell formation are especially dependent on GDI function.

Energy sources for aquatic animals in the Orinoco River floodplain: evidence from stable isotopes.

Stable carbon and nitrogen isotope ratios in autotrophs, aquatic invertebrates and fishes from the Orinoco River floodplain of Venezuela reveal that microalgae, including both phytoplankton and epiphytic (attached) forms, are predominant energy sources for many aquatic animals, even though aquatic vascular plants are much more abundant. Floating mats of the grass Paspalum repens and the water hyacinth Eichhornia spp. harbor particularly high densities of aquatic animals, but isotopic evidence indicates that few species are dependent on organic carbon originating from these plants. The stable isotopic evidence for the trophic importance of algae contradicts traditional interpretations of food webs in freshwater wetlands, which are generally thought to be based largely on detritus originating from vascular plants.

A major food web component in the orinoco river channel: evidence from planktivorous electric fishes.

Deep-water sampling of the Orinoco River main channel resulted in the collection of an unexpectedly high abundance and diversity of specialized fishes. Twenty-eight of the more than 60 species collected belong to the Gymnotiformes(New World electric or knife fishes). One of the more numerous of these, a recently described species of the genus Rhabdolichops, consumes large numbers of very small planktonic Crustacea and insect larvae. These items are captured in the very swift, turbid, and deep waters of the Orinoco. Although the strong dependence of the river food web on terrestrial and floodplain food sources is well known, the specialized capabilities of Rhabdolichops and of other fishes that occur with it indicate a significant extension of the river food web into the main channel.

The cost of sex.

The potential costs of sex can be divided into two large categories. The first category consists of costs that are not derived from anisogamy, and includes costs associated with recombination, with delay of synthesis at the cellular level (cellular-mechanical cost), and with fertilization. The second large category of costs is derived from anisogamy. Specific costs include the cost of genome dilution (cost of males) and the cost of sexual selection. The cost of genome dilution applies to sexual females in anisogamous organisms because the female provides cytoplasm and reserve materials to support the male genome as well as her own genome. The cost of sexual selection is caused by loss of fitness through selection resulting from sexual competition, or through dual phenotypic specialization of a single species as a result of sexual selection. All factors contributing to the cost of sex apply potentially to a broad spectrum of organisms. However, numerous mechanisms reduce the realized cost of sex to a level far below the potential cost. The potential cost is likely to be highest in small organisms, but the realized cost among these organisms is reduced greatly by intermittent sexuality. The realized cost of sex tends to increase with size and complexity among organisms because of increasing commitment to sex with increasing size. Increasing commitment to sex is required by the lower reproductive rates and consequently lower rates of adaptation in larger organisms, which would put such organisms at a disadvantage in relation to smaller organisms were it not for increasing commitment to sexual recombination in larger organisms. Comparable commitment to sex is not possible in smaller organisms because such organisms have a higher potential cost of sex, which maintains among them a lower limit on the frequency of sex.

Late quaternary environmental history of lake valencia, Venezuela.

Chemical, paleontological, and mineralogical analyses of a 7.5-meter core from the middle of Lake Valencia, Venezuela, have provided information on the paleoclimatic history of this low-elevation, low-latitude site for the last 13,000 years. The data show that dry climates existed in this region from 13,000 years before present (B.P.) until about 10,000 years B.P. The Lake Valencia Basin was occupied by intermittent saline marshes at that time. About 10,000 years B.P., a permanent lake of fluctuating salinity formed and arboreal plant communities replaced the earlier dominant xeric herbaceous vegetation and marsh plants. By 8500 years B.P., Lake Valencia reached moderate to low salinities and discharged water; the modern vegetation became established at that time. After 8500 years B.P., the lake twice ceased discharging as a result of reduced watershed moisture. The second of these drying episodes is still in progress and has been aggravated by human activities in the watershed.

Photosynthesis in copepods.

Zooplankton grazers consume appreciable amounts of algae that are not digested. Indigestibility has been considered of adaptive value to the algae and an unqualified disadvantage to the grazer. In Cartesian diver experiments, freshly killed copepods (Acanthocyclops vernalis) produced significant amounts of oxygen when exposed to the light, even after 24 hours of starvation. Also, significant amounts of oxygen were consumed by dead copepods in the dark. These observations suggest that the copepod gut is well suited for photosynthesis by ingested algae.

Acid precipitation in the Western United States.

Precipitation chemistry data from a rural area at an elevation of 2900 meters near the Continental Divide in Colorado show unexpectedly low pH values for bulk precipitation. A significant downward trend in pH over the last 3 years is associated with increasing amounts of nitric acid in precipitation.

Surface/Volume ratio: implications for phytoplankton morphology.

Plankton autotrophs vary greatly in size and shape. Computation of surface/volume ratios for biomass units of 27 coexisting phytoplankton species in a tropical lake indicates that these ratios are conserved within a range much narrower than expected by random choice of shapes. Conservation of surface/volume ratios suggests new explanations for the shapes of phytoplankton biomass units.