Reduced Oxygen Conditions Research Articles

Eimeria tenella: Growth and drug sensitivity in tissue culture under reduced oxygen

For Plasmodium falciparum in culture, growth is enhanced as oxygen tension is lowered and drug susceptibility, particularly susceptibility to 70S ribosomal and mitochondrial inhibitors, changes. Whether similar effects occur in Eimeria tenella was tested as a possible explanation for why certain 70S ribosomal inhibitors, while active in Eimerm-infected birds, are virtually inactive in vitro under ambient oxygen conditions. It was reasoned that perhaps these agents would exhibit good in vitro potency under reduced oxygen conditions. Such proved not to be the case, and it was further found that no positive effect on Eimeria growth occurred under these conditions. Finally, lowering oxygen tension had no substantial effects on sensitivity to anticoccidials or mitochondrial inhibitors.

Phosphorites of Rocinha Mine; Patos de Minas (Minas Gerais, Brazil); genesis and evolution of a middle Proterozoic deposit tectonized by the Brasiliano Orogeny

In central Brazil (the states of Minas Gerais and Goias) the Brasiliano orogeny ([asymp]600 Ma) delineates the Sao Francisco craton and, to the west, the Brasilia fold belt. Rocks of the fold belt are thrust to the east and display increasing deformation and metamorphism westward.Almost all the phosphate deposits are found in the Brasilia fold belt, either along its boundary with the craton or in external structural units showing polycyclic deformation and greenschist metamorphism. They occur in the metasedimentary rocks of the middle Proterozoic Paranoa Group and in the upper Proterozoic Sao Francisco Group and its equivalents. Middle Proterozoic phosphorites are economically the more important. Most are spatially and temporally associated with a stromatolite reef barrier. However, the Rocinha-Patos de Minas deposit, the only presently mined, is located south of the reef barrier. It has developed on a shallow to deep ramp between a wide internal basin with reduced oxygen conditions and limited detritus and a more oxygenated marine environment to the west.In the Rocinha mine, phosphate forms grains, angular fragments, lenses, or centimeterthick beds in schists and carbonate or glauconitic schists. The P 2 O 5 content of phosphatic rocks ranges between 10 and 15 percent. Annual production is around 200,000 tons of ore containing 24 percent P 2 O 5 . The mine area comprises four tectonic slices made up of schists, quartzoschists, and phosphatic schists, separated by subhorizontal shear planes. These are defined by tectonic breccias in which secondary apatite has recrystallized. The mine is exposed in a 50- to 75-m phosphatic sequence which is repeated in a lower slice about 100 m below mine level.The phosphatic ore is a homogeneous crypto- to microcrystalline apatite in fairly continuous centimeter-thick beds which were stretched, fragmented, and boudinaged during Brasiliano isoclinal folding and subsequent subhorizontal shearing.X-ray diffraction, IR spectrometry, and chemical analysis indicate that the metasedimentary phosphate is a weakly carbonated fiuorapatite with low F and CO 2 contents. The influence of the Brasiliano orogenesis is marked by partial substitution of F by OH. Secondary prismatic apatite, kaolinite coatings, and wavellite sheaflike structures are products of weathering and are found in mine sections and bore holes to a depth of 10 to 15 m. Secondary apatites are enriched in CO 2 compared to primary metasedimentary apatites.

Phenotypic characterization of CO2-requiring strains of Streptococcus bovis from koalas

We examined phenotypic characteristics of six mannitol-fermenting strains of Streptococcus bovis, including two unusual CO2-requiring strains isolated from koala feces. These strains did not grow in air, but grew in air supplemented with CO2 and under reduced oxygen conditions. All six strains had the same biochemical characteristics, except that the CO2-requiring strains did not produce beta-N-acetylglucosaminidase.

Physical and biological parameters that determine the fate of p-chlorophenol in laboratory test systems

Shake-flask and microcosm studies were conducted to determine the fate of para-chlorophenol (p-CP) in water and sediment systems and the role of sediment and nonsediment surfaces in the biodegradation process. Biodegradation of p-CP in estuarine water samples in shake flasks was slow over incubation periods of 300 h. The addition of detrital sediment resulted in immediate and rapid degradation evidenced by the production of 14CO2 from [14C]p-CP. The addition of sterile sediment, glass beads, or sand resulted in approximately four to six times more CO2 evolution than observed in the water alone. Densities of p-CP-degrading bacteria associated with the detrital sediment were 100 times greater than those enumerated in water. Bacteria in the water and associated with the sediment after preexposure of both water and sediment of p-CP demonstrated enhanced biodegradation. In some microcosms, p-CP was degraded completely in the top 1.0 cm of intact sediment beds. Sediment reworking activities by benthic invertebrates from one site were sufficient to mix p-CP deep into the sediment bed faster than biodegradation or molecular diffusion. p-CP was persistent at lower depths of the sediment, possibly a result of reduced oxygen conditions preventing aerobic biodegradation.

Respiratory and behavioral responses of the grass shrimp Palaemonetes pugio to cadmium and reduced dissolved oxygen

Adult grass shrimp (Palaemonetes pugio) were collected during July and August, 1973, and exposed for 48-h periods to a series of sublethal cadmium (Cd) concentrations: 0.1 and 0.56 mg l-1 for metabolic studies; and 0.01, 0.05, 0.1, 0.3, 0.56 mg l-1 for locomotor studies. Treatment effects were tested singly and in combination at selected dissolved oxygen (DO) concentrations ranging from near saturation to 0.8 mgl-1. Shrimp not exposed to Cd exhibited metabolic regulation between 6.5 and, 4.6 mg DOl-1, with progressively lower O2 consumption rates at lower DO concentrations. Oxygen consumption of Cd-exposed shrimp was suppressed overall relative to the non-Cd treated shrimp, and with one exception, the magnitude of metabolic suppression directly corresponded to Cd concentration. Locomotor activity of non-Cd exposed shrimp was relatively independent of DO concentration down to 2.8 mg DO l-1 and became significantly suppressed at 1.8 mg DO l-1 and below. Significant suppression of locomotion was evident in shrimp exposed to 0.56 mg Cd l-1, but was not seen in treatment groups of 0.3 mg Cd l-1 or lower. No interaction on locomotor activity of shrimp was detected between Cd exposure and oxygen concentration. The reduction of locomotor activity and metabolism at 0.56 mg Cd l-1 exposure is similar to that occurring under reduced oxygen condition. It is hypothesized that Cd acts in some manner to suppress O2 availability to P. pugio, a suggestion consistent with literature reports on adverse effects of Cd on fish respiratory enzymes and gill tissue.

Another instance of haemoglobin in a flatworm (Phaenocora typhlops Vejdovsky 1880)

Summary(1) The occurrence of haemoglobin in Phaenocora typhlops (Vejdovsky) is reported.(2) Rhabdocoels were examined spectrophotometrically. The distribution of the pigment was studied by a sodium nitroprusside‐benzidine technique, and the distribution of ferric iron with Perl's technique.(3) Characteristic bands of oxyhaemoglobin were observed at 540 and 580 nm. The oxyhaemoglobin was reduced to haemoglobin by the addition of sodium dithionite and an absorption band appeared at about 560 nm.(4) Haematin was found principally around the pharynx, though a little was found in front of the latter and along the length of the gut. Ferric iron was distributed throughout the worm.(5) The occurrence of haemoglobin in P. typhlops and P. unipunctata is compared. It is suggested that less occurs in the former species. Whether or not this is related to the presence of zoochlorellae is considered. Certainly both species burrow actively in mud where reduced oxygen conditions can occur.

Characteristics of the Aerosol Produced from Burning Sodium and Plutonium

Safety analysis of sodium-cooled plutonium-fueled fast reactor plants must be concerned with the possibility of fires involving these materials. Design of an air cleaning system for such a facility requires basic data defining the aerosol characteristics of sodium and plutonium released during a fire. Size characteristics of the aersol produced during sodium and plutonium fires were determined for different atmospheres ranging from 20.8% oxygen, 79.2% nitrogen to 100% nitrogen. The aerosol produced by burning gram quantities of sodium was compared with that produced by a fire involving 600 lb of sodium. Sodium aerosol count median diameter ranged from 0.07 to 1.09 µ and was independent of oxygen concentration. Small and large scale fires produced an aerosol with comparable size characteristics. Plutonium aerosol count median diameter ranged from 0.02 to 0.09 µ and was also independent of oxygen concentration. When plutonium alloy was burned under reduced oxygen conditions, the fraction airborne ranged from 2. × 10-7 to 4. × 10-6. Fires involving plutonium alloy and sodium together produced airborne plutonium-sodium ratios ranging from 0.34 to 0.008%.

THE ROLE OF ADENOSINE TRIPHOSPHATE IN MUSCULAR CONTRACTION.

THE ROLE OF ADENOSINE TRIPHOSPHATE IN MUSCULAR CONTRACTION JACOB SACKS* I. Development ofOpposing Interpretations Adenosine triphosphate, ATP, was firstdiscovered in muscle and is present in that tissue in considerably higher concentration than in any other part of the mammalian organism. There is overwhelming evidence that this substance plays an essential part in the contraction process, but despite the enormous amount ofinvestigation bearing on the point, its exact function is still obscure. Studies on the enzyme systems ofmuscle and on the isolated contractile proteins have given a reasonably consistent picture. However, observations ofthe chemical changes taking place during muscular contraction lead to interpretations at variance with those derived from in vitro studies. The sine qua non ofthe formulation derived from in vitro studies is that the dephosphorylation of ATP to ADP and orthophosphate (Pi) is the immediate source ofthe energy for contraction. Although a few investigators have reported that this reaction takes place in the muscle, the burden offindings from a variety of direct and indirect approaches is that there is no convincing evidence that such a dephosphorylation does take place in the course ofa single twitch or a short tetanic contraction [1-5]. Writers ofreview articles have made diametrically opposite interpretations of the experimental findings. For example, Mommaerts et al. [6] state: "Yet, scientific rigor requires a direct demonstration ofa breakdown ofATP as a reactionimmediately connectedwithcontractionorrelaxation, and, this not having been made, the theory is in a most peculiar position." On the other hand, Perry [7] explains the failure ofChance and Connel- * Department of Chemistry, University ofArkansas, Fayetteville, Arkansas. Part ofthe experimental work referred to was supported by grants from the National Institute ofArthritis and Metabolic Diseases, National Institutes ofHealth. 285 Iy [5] to find any significant increase in ADP content during a single twitch ofisolated frog muscle by stating that the actual changes in ADP concentration were very much greater than those actually measured by the spectrophotometric method used, because ofthe occurrence ofappreciable rephosphorylation by phosphokinases, e.g., creatine kinase. The function ofmusclerequires thatthe rate ofenergy output be capable ofenormous increases within a fraction ofa second. To supply the energy for contraction, it is therefore necessary that there be some source independent ofblood flow and oxygen supply. Because a large part ofthe early investigation was carried out on isolated frog muscle, which has a much greater capacity for survival and function in the absence of oxygen than does mammalian muscle, the development has been in terms ofnon-oxidative reactions. The conversion ofglycogen to lactic acid, the hydrolysis of phosphocreatine (PC), and the dephosphorylation of ATP have successively been identified as the source ofenergy for contraction. The most firm basis for the generally held view—that the dephosphorylation ofATP is the immediate source of the energy for contraction—derives from the finding that myosinhas the properties ofan active ATPase and the demonstration that glycerinated muscle fibers or threads of actomyosin can be made to shorten in the presence of Mg ion upon the addition of ATP. However, the ATPase ofmyosin requires Ca ion for activation and is inhibited by Mg ion. It is now recognized that the complex actomyosin, rather than myosin itself, undergoes this shortening in the isolated system. The ATPase action of actomyosin does require Mg for activation, but seems also to require the presence ofsome free Ca ion [8]. The presence in muscle ofan enzyme which can transfer a phosphate group from PC to ADP, to form ATP, or from ATP to creatine, plus the established finding that a muscle contracting under conditions ofreduced oxygen supply for a series oftwitches, or for a tetanus ofa few seconds ' duration, undergoes a decrease in PC content has been coupled with the shortening offibers induced by ATP in the current formulation. This can be stated in the following terms: the immediate energy for contraction is furnished by the dephosphorylation ofATP to ADP and Pi; the initial reaction in recovery is resynthesis ofthe ATP by transfer ofthe phosphate group ofPC. Muscle also contains a relaxing factor [9, 10] which is isolated from homogenates after removal of the myofibrils. This relaxing factor is a 286 Jacob Sacks · Adenosine Triphosphate in Muscular Contraction Perspectives in Biology and Medicine · Spring 1964 granular material, presumably...