Spin-trapping of superoxide by 5,5-dimethyl-1-pyrroline N-oxide: application to isolated perfused organs

Of the available techniques used to identify free radicals, spin-trapping offers the unique opportunity to simultaneously measure and distinguish among a variety of important biologically generated free radicals. For superoxide and hydroxyl radical, the spin trap 5,5-dimethyl-1-pyrroline 1-oxide (DMPO) is most frequently used. However, this nitrone has several drawbacks. For example, its reaction with superoxide is slow, having a second-order rate constant around 10 M-1 s-1. Because of this, high concentrations of DMPO are essential in order to observe the corresponding spin-trapped adduct, 5,5-dimethyl-2-hydroperoxy-1-pyrrolidinyloxy. This may, in some cases, lead to cellular toxicity. In an attempt to circumvent this serious limitation, it has been proposed that an indirect approach be employed to detect and identify free radicals generated as a consequence of ischemia/reperfusion injury. In the direct (most frequently used) approach, the spin trap is first added to an isolated perfused organ under the appropriate experimental conditions. Then, the infusion buffer containing the spin-trap adduct(s) is placed into an quartz flat cell to be inserted into an ESR spectrometer. In the indirect method, the spin trap is added to the perfusate, which had previously exited the organ. Therefore, with this method one can prevent any spin-trap-mediated toxicities to the isolated perfused organ. However, because of the very rapid rate of free radical reactions catalyzed by either superoxide or hydroxyl radical, it is questionable whether ESR spectra recorded using this indirect method result from the actual spin-trapping of free radicals. In this report, we evaluated the indirect spin-trapping technique in light of the kinetic considerations discussed above.     

Postrhinoplasty "red nose": differential diagnosis and treatment by laser

Prior to anticipated nasal surgery, the nasal and facial skin should be examined for any vascular lesions. The skin type should be ascertained. A history of any prior nasal surgery, particularly on the nasal dorsum, should be noted. If rosacea is a clinical possibility, a trial of 1.5 to 2.0 gm q.d. of tetracycline for 6 to 8 weeks is warranted. If, after rhinoplasty, a diffuse "redness" on the nasal dorsum results and one can exclude other diagnoses, then argon laser therapy should be considered. A 3-mm punch biopsy should be obtained to see whether superficial ectatic vessels are present, a finding that would be indicative of a good result from laser therapy.     

Nematology—Status and Prospects: Let's Take Off Our Blinders and Broaden Our Horizons

Some aspects of current fundamental nematological research and teaching in agriculture, soil zoology, biology and medicine, and parasitology are explored as they relate to the Society of Nematologists and the science of nematology in its broadest sense.     

Vasopressin content of rat brain

Vasopressin was extracted and measured from various areas of rat brain. Vasopressin in quantities many times that in circulating blood was found in most areas of brain except for cerebellum. The highest concentration of vasopressin were found in the amygdala, septum, thalamus and striatum. Homozygous Brattleboro rat brain contained negligible amounts of vasopressin. The rat brain extract reacted identically with standard vasopressin in the radioimmunoassay over a 40-fold dilution range and migrated with vasopressin on Sephadex G-25 chromatography.     

Genes and sites involved in replication and incompatibility of an R100 plasmid derivative based on nucleotide sequence analysis

Summary The nucleotide sequence of the entire region required for autonomous replication and incompatibility of an R100 plasmid derivative, pSM1, has been determined. This region includes the replication region and all plasmid encoded information required for replication. Numerous reading frames for possible proteins can be found in this region. The existence of one of these proteins called RepA1 (285 amino acids; 33,000 daltons) which is encoded within the region known by cloning analysis to be required for replication is supported by several lines of evidence. These include an examination of the characteristic sequences on the proximal and distal ends of the coding region, a comparison of the sequence of the replication regions of pSM1 and the highly related R1 plasmid derivative Rsc13 as well as other biochemical and genetic evidence. The existence of two other proteins, RepA3 (64 amino acids; 7000 daltons) and RepA2 (103 amino acids; 11,400 daltons) is also consistent with most of the criteria mentioned above. However, the region encoding RepA3, which by cloning analysis is within the region responsible for both replication and incompatibility, has never been demonstrated to produce a 7,000 dalton polypeptide. Since a large secondary structure can be constructed in this region, it is possible that the region contains structure or other information that is responsible for incompatibility. RepA2, encoded entirely within the region identified by cloning analysis to be responsible for incompatibility but not for replication can be visualized in vivo and in vitro. However, the nucleotide sequence of the region encoding RepA2 is completely different in mutually incompatible plasmid derivatives of R1 and R100. It is therefore unlikely that RepA2 plays a major role in incompatibility. Thus, we predict that RepA1 is required to initiate DNA synthesis at the replication origin and that the region proximal to RepA1 either encodes a gene product or structure information that is responsible for incompatibility.     

13C-nuclear magnetic resonance spectra of compounds containing β-D-fructofuranosyl groups or residues

¹³C-N.m.r. spectra have been recorded for sucrose, melezitose, levan, inulin, palatinose, and D-fructose. Except for the last, each compound contains a different O-substituted D-fructofuranose residue or group, or β-D-fructofuranosyl residue or group. On the basis of chemical-shift displacements, resulting from O-substitution at specific carbon atoms, resonances can be assigned to the carbon atoms of the β-D-fructofuranosyl residue. Fortuitously, the α-D-glucopyranosyl group present in some of these compounds exhibits resonances that do not obscure the β-D-fructofuranosyl resonances. O-Substitution of the β-D-fructofuranosyl residue causes a downfield displacement of the corresponding, linked-C resonance; however, the other major resonances of this residue are not affected by bulky substituents. Members of a series of levan fractions, the products of partial, acid hydrolysis of Streptoccoccus salivarius levan, were then examined for changes in relative degree of branching.     

Properties and function of the proton-translocating adenosine triphosphatase of Clostridium perfringens.

Growth of Clostridium perfringens was inhibited by compounds which dissipate or prevent the formation of electrochemical proton gradients. Membrane vesicles prepared from this organism exhibited Mg2+-dependent adenosine triphosphatase (ATPase) activity sensitive to N,N'-dicyclohexylcarbodiimide. Mg2+-ATPase activity was optimal of 50 degrees C, but no discrete pH optimum was observed. Adenosine triphosphate-dependent quenching of the fluorescence of the weak base quinacrine by everted membrane vesicles suggested that the Mg2+-ATPase is a proton pump capable of generating an electrochemical proton gradient. Adenosine triphosphate-dependent transport of Ca2+ by everted vesicles was sensitive to uncouplers and inhibitors of the Mg2+-ATPase.     

Measurement of stagnancy in a pipe line using a radioactive tracer and labelled bacteria

Summary A stainless steel T joint was used to simulate stagnant volume in a pipe-line. Residence time distribution in the lines was measured using a radiotracer (Cr⁵¹) which emitted radiation. The radiation was measured externally to the pipe line. From the experimental data the dead volume of the system was calculated. The effect of the depth of T and flow velocity on dead volume was evaluated. Labelled bacteria were used in some experiments instead of chromium. No significant difference in behavior between ionic chromium and bacteria labeled with chromium was found.