The effect of xanthate floatation reagents on bacterial leaching of chalcopyrite by Thiobacillus ferrooxidans

Summary Xanthate floatation compounds, added to cultures of Thiobacillus ferrooxidans leaching chalcopyrite, inhibited growth in the concentration range 1–10 mM and caused a drop in formation of soluble copper and iron. Maximum (80–90%) growth inhibition was at 10 mM for isobutyl-, amyl- and ethyl xanthate while isopropyl xanthate was innocuous but caused a four-fold increase in lag phase. Copper production was depressed by 30% for isopropyl-, 53% for isobutyl-, ethyl- and 77% for amyl xanthate at 10 mM additions.     

Enhanced thermotolerance by hydrostatic pressure in the deep-sea hyperthermophile Pyrococcus strain ES4

Abstract: The combined effect of hydrostatic pressure and heat shock on thermotolerance was examined in the deep-sea hyperthermophilic archaeon Pyrococcus strain ES4. Pressure equivalent to the depth of isolation (22 MPa) enhanced ES4's survival at super-optimal temperatures (101–108°C) relative to low pressure (3 MPa). Pressure also raised the temperature at which a putative heat-shock protein (98 kDa) accumulated. ES4 grown at 95°C and 3 MPa displayed immediate enhanced thermotolerance to 105°C after being shifted to 22 MPa. Cultures grown at 95°C and 22 MPa and then heat shocked at 105°C and 3 MPa retained enhanced thermotolerance after decompression. These results suggest that this deep-sea hyperthermophile has developed pressure-induced responses that include increased survival to hyperthermal conditions.     

Bradykinin antagonists: Development and applications

Bradykinin (BK) is involved in regulation of every major physiological system and is an initiator or mediator of many pathophysiological conditions. Rapid progress in understanding these aspects of BK biology has come since the discovery of BK antagonists. This article reviews principal points in the history of the kallikrein–kinin field and of kinin biology. The chemistry and development of antagonists for B1 and B2 kinin receptors is discussed. Uses of the antagonists in biomedical research and potential clinical applications are presented. © 1994 John Wiley & Sons, Inc.     

Induction of diapausing amictic eggs in Synchaeta pectinata

Amictic females of a clone of S. pectinata from Star Lake (Norwich, Vermont) may produce diapausing as well as non-diapausing (subitaneous) eggs. The proportion of diapausing eggs produced in cultures was unaffected by temperature (12 vs 19 °C) or rotifer population density (minima of 0.33 vs 3 ind. ml^–1) at 19 °C. However, at 19 °C this proportion was higher in cultures maintained at a low food level suppressing reproduction (5 × 10³ cells ml^–1 Cryptomonas erosa) than in those maintained at a high food level (2 × 10⁴ cells ml^–1); the treatment effect was marginally significant (p=0.067). Consistent with the effect of low food availability, a period of starvation was very effective in inducing the development of diapausing eggs. None of 19 females cultured individually from hatching at 19 °C on C. erosa (2 × 10⁴ cells ml^–1) in 1-ml volumes produced any diapausing eggs in 4 days (0 out of 349 eggs), while 13 out of 16 females subjected to a 15-hour starvation period 6 hours after birth produced one or more diapausing eggs during that time (34% of the 158 eggs produced by the 16 females were diapausing). Diapausing eggs produced and left at 19 °C hatched after 4 to 13 days. Those produced in cultures with a low food level took significantly longer to hatch (9.7 days) than those produced in cultures with a high food level (8.1 days) (p=0.022). In natural communities, S. pectinata should be able to respond directly and rapidly to poor food conditions by producing eggs that undergo an obligatory dormant period before resuming development.     

Computer determination of perfusion patterns in pulmonary capillary networks

Hanger, Christopher C., Robert G. Presson, Jr., Osamu Okada,Steven J. Janke, John J. Watkins, Wiltz W. Wagner, Jr., and Ronald L. Capen. Computer determination of perfusion patterns in pulmonarycapillary networks. J. Appl. Physiol.82(4): 1283-1289, 1997.Individual pulmonary capillaries are notsteadily perfused. By using in vivo microscopy, it can readily bedemonstrated that perfusion continually switches between capillarysegments and between portions of the network within a single alveolarwall. These changes in capillary perfusion occur even when upstream pressure and flow are constant. Flow switching between capillary segments in the absence of hemodynamic changes in large upstream vessels suggests that capillary perfusion patterns could be random. Tocalculate the probability that perfusion patterns could occur bychance, it is necessary to know the total number of possible perfusionpatterns in a given capillary network. We developed a computer programthat can determine every possible perfusion pattern for any givencapillary network, and from that information we can calculate whetherperfusion of individual segments in the network is random. With theresults of the computer program, we have obtained statistical evidencethat some capillary segments in a network are nonrandomly perfused.

     

Production of gliotoxin during the pathogenic state in turkey poults byAspergillus fumigatus Fresenius

Turkey poults were given either of two different dosages of two different gliotoxin-producing strains ofAspergillus fumigatus. Infected lung tissue was examined postmortem for the presence of gliotoxin. Gliotoxin was found in lung tissue of ten poults infected with one strain and in seven of ten poults infected with the other strain. Concentrations of gliotoxin in the tissue exceeded 6 ppm in some of the infected tissues. The concentration of gliotoxin found in infected tissue did not appear to be correlated with the dosage of organism given. Considering the pathologic changes observed in turkey poults with aspergillosis and the production of gliotoxin during the pathogenic state in turkey poults, gliotoxin is considered likely to be involved in avian aspergillosis. Disclaimer: Names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by USDA implies no approval of the product to the exclusion of others that may also be suitable.     

Energy-dispersive X-ray analysis of the extracellular cadmium sulfide crystallites of Klebsiella aerogenes

Klebsiella aerogenes forms electron-dense partieles on the cell surface in response to the presence of cadmium ions in the growth medium. These particles ranged from 20 to 200 nm in size, and quantitative energy dispersive X-ray analysis established that they comprise cadmium and sulfur in a 1:1 ratio. This observation leads to the conclusion that the particles are cadmium sulfide crystallites. A combination of atomic absorption spectroscopy, inductively coupled plasma mass spectrometry, and acid-labile sulfide analysis revealed that the total intracellular and bound extracellular cadmium:sulfur ratio is also 1:1, which suggests that the bulk of the cadmium is fixed as extracellular cadmium sulfide. The tolerance of K. acrogenes to cadmium ions and the formation of the cadmium sulfide crystallites were dependent on the buffer composition of the growth medium. The addition of cadmium ions to phosphate-buffered media resulted in cadmium phosphate precipitates that remove the potentially toxic cadmium ions from the growth medium. Electrondense particles formed on the surfaces of bacteria grown under these conditions were a combination of cadmium sulfide and cadmium phosphates. The specific bacterial growth rate in the exponential phase of batch cultures was not affected by up to 2mM cadmium in Tricine-buffered medium, but formation of cadmium sulfide crystallites was maximal during the stationary phase of batch culture. Cadmium tolerance was much lower (10 to 150 M) in growth media buffered with Tris, Bistris propane, Bes, Tes, or Hepes. These results illustrate the importance of considering medium composition when comparing levels of bacterial cadmium tolerance.Abbreviations EDXA Energy dispersive X-ray analysis - AAS Atomic absorption spectroscopy - TEM Transmission electron microscopy - SEM Scanning electron microscopy - ICP-MS Inductively coupled plasma mass spectrometry - ALSA Acid-labile sulfide analysis