Opportunistic zygomycotic infections

This is a literature review of 361 opportunistic fungal infections caused by the Zygomycetes. The clinical and laboratory diagnosis, pathogenesis, management, treatment, and outcome of infection are discussed. The Zygomycetes are a group of opportunistic fungi (orders Mucorales and Entomophthorales) which cause severe infections which may be fatal. Early clinical recognition, prompt diagnostic procedures, control of underlying disease and treatment with high doses of amphotericin B and aggressive surgery increases survival in an otherwise lethal infection.     

Nucleotide sequence of the DdeI restriction-modification system and characterization of the methylase protein.

The DdeI restriction-modification system was previously cloned and has been maintained in E. coli on two separate and compatible plasmids (1). The nucleotide sequence of the endonuclease and methylase genes has now been determined; it predicts proteins of 240 amino acids, Mr = 27,808, and 415 amino acids, Mr = 47,081, respectively. Inspection of the DNA sequence shows that the 3' end of the methylase gene had been deleted during cloning. The clone containing the complete methylase gene was made and compared to that containing the truncated gene; only clones containing the truncated form support the endonuclease gene in E. coli. Bal-31 deletion studies show that methylase expression in the Dde clones is also dependent upon orientation of the gene with respect to pBR322. The truncated and complete forms of the methylase protein were purified and compared; the truncated form appears to be more stable and active in vitro. Finally, comparison of the deduced amino acid sequence of M. DdeI with that of other known cytosine methylases shows significant regions of homology.     

Effect of nutritional copper deficiency on carrageenin edema in the rat

The effects of nutritional copper deficiency on carrageenin edema in the rat were investigated with emphasis on studying the correlation between the degree of copper deficiency and the degree of edema. Carrageenin paw edema in both copper-sufficient and copper-deficient groups of rats was compared after either 20, 40, or 60 d on respective diets. The degree of copper deficiency was quantitated by analyzing total copper concentrations in a number of tissues. Other copper dependent parameters were also determined. Results indicated that: (1) although copper sufficient rats showed relatively little change in the degree of edema, copper-deficient rats showed a steady and significant increase in edema from d 20 to 40 to 60; (2) paw edema in copper-deficient animals was highly and negatively correlated to the concentrations of copper in the liver; the correlation with liver Cu,Zn-superoxide dismutase activity, however, was inconsistent; (3) paw edema was not correlated either to copper concentration in tissues other than liver or to plasma ceruloplasmin activity; and (4) aggravation of carrageenin edema in copper-deficient animals seemed to be mediated via an as yet unknown secondary effect of copper deficiency.     

Cloning and expression of the toxin B gene ofClostridium difficile

Results from our cloning studies on toxin A indicated that the gene for toxin B resided approximately 1 kb upstream of the toxin A gene. Clone pCD19, which contains the 5-end of the toxin A gene and a small open reading frame, was found to contain 1.2 kb of DNA which, when subcloned, expressed a nontoxic peptide that reacted with toxin B antibodies. The rest of the toxin B gene was located on the 6.8 kb cloned fragment of plasmid pCD19L. The two fragments overlapped 0.8 kb. Lysates containing protein expressed by the 6.8 fragment were cytotoxic and lethal, and were neutralized by toxin B antibody. The two fragments were ligated to give the complete toxin B gene. The protein expressed by the complete gene was cytotoxic and lethal, and showed complete immunological identity with toxin B. Further analysis of the expressed protein and the toxin B gene confirmed our earlier findings showing that toxin B has a molecular weight of 240,000 or greater.     

Effects of methotrexate-carcinoembryonic-antigen-antibody immunoconjugates on GW-39 human tumors in nude mice

Summary Methotrexate (MTX) was conjugated to an anti-carcinoembryonic antigen monoclonal antibody (NP2) by using amino-dextran as an intermediate carrier. The drug was chemically linked to amino-dextran (averageM _r = 40000), and the resulting MTX-dextran was then site-specifically attached to the carbohydrate moiety of the antibody. Athymic nude mice that carried human colonic GW-39 tumors (s. c.) were treated with the immunoconjugate. In this study, the specific conjugate caused a greater inhibition of the tumor growth than either free MTX or its conjugate with dextran and an irrelevant antibody. The intermediate MTX-dextran and the unlinked mixture of MTX-dextran with NP2 were both relatively ineffective in inhibiting tumor growth. The greatly reduced host toxicity permitted the use of the MTX-dextran-NP2 in a high-dose therapy of this tumor system.Supported in part by U.S.P.H.S. grant CA39 841 from the NIH     

Differences between arterial and mixed venous levels of plasma hydroperoxides following major thoracic and abdominal operations

Fatty acid hydroperoxides in the plasma of 18 patients who were undergoing normal postoperative periods following major thoracic or abdominal operations were measured by using a sensitive assay based upon the activation of the cyclooxygenase activity of prostaglandin H synthase. Following major thoracic operations of nine patients, the mean difference between the arterial (0.49 ± 0.13 μM, mean ± S.E.M.) and mixed venous (−0.09 ± 0.12 μM) level of hydroperoxide was 0.58 ± 0.13 μM (p < 0.01). In marked contrast to this result, major abdominal operations of nine patients led to a mean difference between the arterial (−0.19 ± 0.16 μM) and mixed venous (0.46 ± 0.08 μM) hydroperoxide levels of −0.65 ± 0.17 μM (p < 0.01). Both pulmonary and intraabdominal tissues appear capable of generating significant amounts of fatty acid hydroperoxide in response to standard surgical procedures. The A-MV differences suggest that the blood-borne hydroperoxides were rapidly cleared from the circulation by tissue capillary beds.     

Prochlorococcus marinus nov. gen. nov. sp.: an oxyphototrophic marine prokaryote containing divinyl chlorophyll a and b

Several years ago, prochlorophyte picoplankton were discovered in the N. Atlantic. They have since been found to be abundant within the euphotic zone of the world's tropical and temperate oceans. The cells are extremely small, lack phycobiliproteins, and contain divinyl chlorophyll a and b as their primary photosynthetic pigments. Phylogenies constructed from DNA sequence data indicate that these cells are more closely related to a cluster of marine cyanobacteria than to their prochlorophyte relatives Prochlorothrix and Prochloron. Several strains of this organism have recently been brought into culture, and herewith are given the name Prochlorococcus marinus.     

Seasonal carbon isotope discrimination in a grassland community

Summary Grassland communities of arid western North America are often characterized by a seasonal increase in ambient temperature and evaporative demand and a corresponding decline in soil moisture availability. As the environment changes, particular species could respond differently, which should be reflected in a number of physiological processes. Carbon isotope discrimination varies during photosynthetic activity as a function of both stomatal aperture and the biochemistry of the fixation process, and provides an integrated measure of plant response to seasonal changes in the environment. We measured the seasonal course of carbon isotope discrimination in 42 grassland species to evaluate changes in gas exchange processes in response to these varying environmental factors. The seasonal courses were then used to identify community-wide patterns associated with life form, with phenology and with differences between grasses and forbs. Significant differences were detected in the following comparisons: (1) Carbon isotope discrimination decreased throughout the growing season; (2) perennial species discriminated less than annual species; (3) grasses discriminated less than forbs; and (4) early flowering species discriminated more than the later flowering ones. These comparisons suggested that (1) species active only during the initial, less stressful months of the growing season used water less efficiently, and (2) that physiological responses increasing the ratio of carbon fixed to water lost were common in these grassland species, and were correlated with the increase in evaporative demand and the decrease in soil moisture.     

Long-range walking techniques in positional cloning strategies

Conclusion The past several years have seen an explosive growth in our understanding of the organization and structure of mammalian genomes, and refinements of existing techniques for genetic analysis, physical mapping, and large-fragment cloning techniques may well be enough to continue the momentum of that explosion for some time to come. Although refinement of existing techniques will certainly be necessary, the development of new and better cloning techniques may, perhaps, no longer be our most urgent need. The most important challenge that we face at present may in fact be that of finding efficient ways to share existing resources and information rapidly and equitably throughout the scientific community so that progress can continue unimpeded, and to catalog, correlate, and interpret the wealth of new data that is so rapidly accumulating.New strategies aimed at whole-genome mapping (Coulson et al. 1986, 1988; Michiels et al. 1987; Brenner and Livak 1989; Carrano et al. 1989; Lehrach et al. 1991) and sequencing (Church and Keifer-Higgins 1988; Bains and Smith 1988; Drmanac et al. 1989; Strzoska et al. 1991) may someday make the current method of long-range walking and physical mapping nearly passe. For example, since most of the relatively small nematode genome is now stored as ordered sets of cosmid and YAC clones (Coulson et al. 1986, 1988), a walk between a mapped marker and an uncloned gene can be accomplished rapidly, through a request for the appropriate series of clones from the ordered library. Vigorous drives by many laboratories to produce ordered clone libraries for murine and human chromosomes (Lehrach et al. 1991) may transform the process of cloning mammalian genes into a relatively trivial matter within the foreseeable future. The remarkable number of positional-cloning successes that have been reported in recent years may indicate that most of the best-defined, simply inherited mouse mutations and human hereditary disorders will have already been cloned by that time. When that is accomplished, the true challenging task will just begin: we must learn to decipher the complex biological programs encoded by our large and ever-growing storehouse of cloned, mapped and sequenced genes, before we can begin to understand what might be held in the vast silent mass of mammalian genomes. Offprint requests to: L. Stubbs