Unusual case of tracheal agenesis

We describe the clinical presentation and pathological features of an unusual case of tracheal agenesis. The axial derivatives of the primitive foregut between the larynx and stomach were represented by a single structure featuring sequential segmentation into regions showing exclusively tracheal or esophageal differentiation in a pattern that is not easily classified by existing nosologic systems nor explained by the conventional hypothesis of dysontogenesis.     

Increased carotenoid production by the food yeast Candida utilis through metabolic engineering of the isoprenoid pathway

The yeast Candida utilis does not possess an endogenous biochemical pathway for the synthesis of carotenoids. The central isoprenoid pathway concerned with the synthesis of prenyl lipids is present in C. utilis and active in the biosynthesis of ergosterol. In our previous study, we showed that the introduction of exogenous carotenoid genes, crtE, crtB, and crtI, responsible for the formation of lycopene from the precursor farnesyl pyrophosphate, results in the C. utilis strain that yields lycopene at 1.1 mg per g (dry weight) of cells (Y. Miura, K. Kondo, T. Saito, H. Shimada, P. D. Fraser, and N. Misawa, Appl. Environ. Microbiol. 64:1226-1229, 1998). Through metabolic engineering of the isoprenoid pathway, a sevenfold increase in the yield of lycopene has been achieved. The influential steps in the pathway that were manipulated were 3-hydroxy methylglutaryl coenzyme A (HMG-CoA) reductase, encoded by the HMG gene, and squalene synthase, encoded by the ERG9 gene. Strains overexpressing the C. utilis HMG-CoA reductase yielded lycopene at 2.1 mg/g (dry weight) of cells. Expression of the HMG-CoA catalytic domain alone gave 4.3 mg/g (dry weight) of cells; disruption of the ERG9 gene had no significant effect, but a combination of ERG9 gene disruption and the overexpression of the HMG catalytic domain yielded lycopene at 7.8 mg/g (dry weight) of cells. The findings of this study illustrate how modifications in related biochemical pathways can be utilized to enhance the production of commercially desirable compounds such as carotenoids.     

Oxidant mechanisms in toxic acute renal failure

Setting up a puppy training program is one of the most important services veterinarians can offer. Puppy socialization classes aim not only to socialize the puppies so that they learn to interact well with children, adults, and other dogs, but also to teach basic obedience exercises. The classes build a strong bond between puppy, owner, and veterinary clinic. This article covers the techniques used, the structure of the classes, and outlines benefits for the dog, owner, veterinarian, and community.     

Energy conservation in compressed‐air systems

In this paper, we evaluate and quantify the energy losses associated with compressed‐air systems, and their costs to manufacturers. We also show how to reduce the cost of compressed air in existing facilities by making some modifications with attractive payback periods. Among the measures, we investigate to reduce the compressed air are: (1) repairing air leaks, (2) installing high‐efficiency motors, (3) reducing the average air inlet temperature by using outside air (4) reducing compressor air pressure. We also illustrate the potential saving associated with each measure by using realistic examples. Copyright © 2002 John Wiley & Sons, Ltd.     

Methanogenium frigidum sp. nov., a psychrophilic, H2-using methanogen from Ace Lake, Antarctica

Methanogenium frigidum sp. nov. was isolated from the perennially cold, anoxic hypolimnion of Ace Lake in the Vesfold Hills of Antarctica. The cells were psychrophilic, exhibiting most rapid growth at 15 degrees C and no growth at temperatures above 18 to 20 degrees C. The cells were irregular, nonmotile coccoids (diameter, 1.2 to 2.5 microns) that occurred singly and grew by CO2 reduction by using H2 as a reductant. Formate could replace H2, but growth was slower. Acetate, methanol, and trimethylamine were not catabolized. Cells grew with acetate as the only organic compounds in the culture medium, but growth was much faster in medium also supplemented with peptones and yeast extract. The cells were slightly halophilic; good growth occurred in medium supplemented with 350 to 600 mM Na+, but no growth occurred with 100 or 850 mM Na+. The pH range for growth was 6.5 to 7.9; no growth occurred at pH 6.0 or 8.5. Growth was slow (maximum specific growth rate, 0.24 day-1; doubling time, 2.9 days). This is the first report of a psychrophilic methanogen growing by CO2 reduction.