Enhanced Survival of the Cyanobacterium Oscillatoria terebriformis in Darkness under Anaerobic Conditions

Oscillatoria terebriformis, a thermophilic cyanobacterium, maintained viability in darkness under anaerobic conditions by fermenting exogenous glucose or fructose to lactic acid. The time period of survival was greatly extended when the environmental redox potential was lowered by the addition of sodium thioglycolate or titanium(III) citrate. When exposed to aerobic conditions in darkness, many trichomes underwent lysis in 6 h, and death of all cells occurred in 2 to 3 days. The endogenous aerobic respiration rate was high, and the limited dark aerobic survival period appeared to be due to depletion of stored glycogen. Fructose or glucose did not support or increase aerobic respiration in darkness or lengthen aerobic survival time. Enhanced survival of O. terebriformis in darkness under anaerobic, reducing conditions correlates well with the natural nighttime position of this species within sulfide-rich microbial mats associated with hot springs of western North America.     

Interleukin 1 preferentially stimulates the production of tissue-type plasminogen activator by human articular chondrocytes

Interleukin 1, derived from human placenta, stimulates plasminogen activator activity in human articular chondrocytes. The stimulation of plasminogen activator activity can be abolished by preincubation of placental interleukin 1 with an antiserum to homogeneous 22K factor, a species of interleukin 1 beta, indicating that the stimulation of plasminogen activator activity is due to interleukin 1 and not contaminating factors. Chondrocytes produce three species of plasminogen activator, with apparent Mr approximately 50,000, 65,000 and 100,000 as determined after sodium dodecyl sulphate (SDS)-polyacrylamide gel electrophoresis with gels containing casein and plasminogen. Both placental interleukin 1 and 22K factor enhance the production of the species of Mr approximately 65,000 and 100,000. Comparison of the mobility of the plasminogen activator species on SDS-polyacrylamide gel electrophoresis with human urokinase (u-PA) and human melanoma tissue-type plasminogen activator (t-PA) and studies with antibodies to these enzymes indicate that the Mr approximately 50,000 species is a u-PA and the Mr approximately 65,000 a t-PA. The Mr approximately 100,000 species is possibly an enzyme-inhibitor complex. Interleukin 1 therefore appears to enhance the production of t-PA and a putative enzyme-inhibitor complex. Abolition of plasminogen activator activity in the fibrin plate assay with antibodies to t-PA and u-PA also confirms enhanced t-PA production on interleukin 1 stimulation, though there is also evidence for increased cell-associated production of u-PA.     

The accountant as triage master: an economist's perspective on voluntary euthanasia and the value of life debate

The author, an economist, rebuts the contention that human life cannot and should not be economically evaluated and argues that such evaluations are made implicitly and inconsistently, resulting in a reduction of human welfare. He presents an economic framework for the analysis of costs and benefits in which the focal point, as in most value systems, is the tradeoff between life and quality of life. Therefore, as the quality of life decreases, society's efforts to preserve life should decrease. If the valuation of life includes self evaluation, then there should be less effort to preserve the life of an individual who wishes to die. Richardson concludes that voluntary euthanasia is a limiting case in which society accepts the individual's valuation of life.     

Fermentation of barley straw by anaerobic rumen bacteria and fungi in axenic culture and in co-culture with methanogens

When incubated in axenic culture, strains of anaerobic rumen fungi were more active than cellulolytic bacteria in solubilizing barley straw stem fragments 5 to 10 mm in length. Pretreatment with ammonia had little effect on microbial attack. Of three species of methanogens tested, Methanobrevibacter smithii strain PS formed the most stable and reproducible co-cultures with the fungi and with Ruminococcus albus , and the presence of this organism enhanced the extent of degradation of straw, although this effect was less marked than that previously observed when pure cellulose was used as substrate.     

Chemokinetic Motility Responses of the Cyanobacterium Oscillatoria terebriformis

Oscillatoria terebriformis, a gliding, filamentous, thermophilic cyanobacterium, exhibited an inhibition of gliding motility upon exposure to fructose. The observed response was transient, and the duration of nonmotility was directly proportional to the concentration of fructose. Upon resumption of motility, the rate of motility was also inversely proportional to the concentration of fructose. Sulfide caused a similar response. The effect of sulfide was specific and not due to either anoxia or negative redox potential. Exposure to glucose, acetate, lactate, or mat interstitial water did not elicit any motility response.     

Isolation and characterization of the cDNA for pulmonary surfactant-associated protein-B (SP-B) in the rabbit

Pulmonary surfactant contains phospholipids including dipalmitoyl-phosphatidylcholine and three surfactant-associated proteins designated SP-A, SP-B and SP-C. A cDNA for rabbit SP-B has been isolated from a fetal (30 days gestation) rabbit lung cDNA library constructed in lambda gt11. The cDNA and deduced amino acid sequences show strong homology with the cDNAs and predicted 40 kDa proproteins for human and canine SP-B. Strong homology is also observed with the amino acid sequences directly determined for the mature 8 kDa bovine and porcine SP-B isolated from lung lavage. SP-B is remarkable for its high cysteine and proline content and for the hydrophobic nature of the organic solvent-soluble, mature protein. In vitro translation of sense but not antisense RNA transcribed from the cDNA led to the production of 40 kDa and 32 kDa proteins. These proteins were immunoprecipitated by an antibody raised against bovine SP-B. Northern blot analysis revealed the mRNA for rabbit SP-B appears in fetal rabbit lung late in gestation and falls slightly in the neonate.     

Site-specific integration in Streptomyces ambofaciens: localization of integration functions in S. ambofaciens plasmid pSAM2.

In Streptomyces ambofaciens ATCC 15154, an 11.1-kilobase element, pSAM2, exists as a single integrated copy in the chromosome. In S. ambofaciens 3212 (a derivative of ATCC 15154), pSAM2 exists as a free, circular plasmid as well as an integrated element. BclI fragments from the free form of pSAM2 were cloned into an Escherichia coli plasmid vector. By using gene transplacement methods, the chromosomally integrated form of pSAM2 was marked with a gene coding for apramycin resistance. This enabled us to isolate both a segregant that had lost the integrated pSAM2 element and a cosmid clone containing integrated pSAM2 along with the flanking chromosomal sequences. One of the BclI fragments derived from free pSAM2 was shown to contain all the plasmid-specified information required to direct site-specific recombination in a derivative of S. ambofaciens lacking the resident pSAM2 element as well as in a number of other Streptomyces strains. The attachment sites used by the plasmid and the chromosome in site-specific recombination and the junctions created after integration were cloned and sequenced. Certain structural features in common with other integrating elements in actinomycetes were noted.     

Role of arginine 180 and glutamic acid 177 of ricin toxin A chain in enzymatic inactivation of ribosomes.

The gene for ricin toxin A chain was modified by site-specific mutagenesis to change arginine 180 to alanine, glutamine, methionine, lysine, or histidine. Separately, glutamic acid 177 was changed to alanine and glutamic acid 208 was changed to aspartic acid. Both the wild-type and mutant proteins were expressed in Escherichia coli and, when soluble, purified and tested quantitatively for enzyme activity. A positive charge at position 180 was found necessary for solubility of the protein and for enzyme activity. Similarly, a negative charge with a proper geometry in the vicinity of position 177 was critical for ricin toxin A chain catalysis. When glutamic acid 177 was converted to alanine, nearby glutamic acid 208 could largely substitute for it. This observation provided valuable structural information concerning the nature of second-site mutations.     

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains

Rhodobacter capsulatus strain BK5 possesses a membrane bound respiratory nitrate reductase rather than the periplasmic enzyme found in other strains. The enzyme in strain BK5 is shown to be both functionally and structurally related to the nitrate reductase of Paracoccus denitrificans and Escherichia coli.Abbreviation TMAO trimethylamine-N-oxide