Indium-111 autologous leucocyte scanning: comparison with radiology for imaging the colon in inflammatory bowel disease.

Indium-111 autologous leucocyte scanning was compared with barium enema for assessing the extent of colonic disease in Crohn''s colitis and ulcerative colitis. Scanning was shown to be as accurate as conventional radiology in colitis, reliably distinguishing active from inactive disease. The results suggest that 111In-leucocyte scanning is an accurate, non-invasive, alternative technique for imaging the extent of disease in colitis.     

Regulation of lysine- and lysine-plus-threonine-inhibitable aspartokinases in Bacillus brevis.

Further studies on the expression of the two aspartokinase activities in Bacillus bovis are presented. Aspartokinase I (previously shown to be inhibited and repressed by lysine) was found to be repressed by diaminopimelate in the wild-type strain. However, in a mutant unable to convert diaminopimelate to lysine, starvation for lysine resulted in an increase in aspartokinase I activity. Thus, lysine itself or an immediate metabolite was the true effector of repression. Aspartokinase II (previously shown to be inhibited by lysine plus threonine) was repressed by threonine. Studies with the parent strain and auxotrophs inidicated that only threonine or an immediate metabolite of threonine was involved in this repression. Methionine and isoleucine were not effectors of any of the detected aspartokinase activities. Apart from inhibition and repression controls, a third as yet undefined regulatory mechanism operated to decrease the levels of both aspartokinases as growth declined, even in mutants in which repression control was absent. In thiosine-resistant, lysine-excreting mutants with elevated levels of aspartokinase, the increase in activity could always be attributed to one enzyme or the other, never both. The existence of separate structural genes for each aspartokinase is therefore suggested.     

The mechanism of the activity-dependent luminescence of xanthine oxidase.

The weak luminescence that accompanies the aerobic xanthine oxidase reaction is inhibited by superoxide dismutase, by catalase, and by scavengers of hydroxyl radicals. It is also entirely dependent upon the presence of carbonate. It thus appears that the O₂ and H₂O₂ produced during the aerobic action of xanthine oxidase interact to generate OH which, in turn, reacts with carbonate to yield the carbonate radical (CO₃^?). The species that is directly responsible for light emission appears to be produced by a dimerization of carbonate radicals, since the light intensity was a function of the square of the carbonate concentration. The data provide no reason to suppose that the light-emitting species is singlet oxygen.     

Properties of Go cells: variations in the proliferative response following isoprenaline.

The proliferative behaviour induced in the acinar cells of the rat submaxillary gland in response to isoprenaline has been used to examine the transit time of cells from a quiescent (Go) state into the S phase. Cumulative 3H-TdR labelling index curves were constructed to determine the mean time interval (Gis time) between stimulation with isoprenaline and entry into the S phase. Data were collected for the proliferative wave induced by three sequential injections of isoprenaline, and the effects of varying the interval between the second and third injections of isoprenaline, and of changing the dose of the drug, were examined. Intervals of 28, 52 and 76 hr between isoprenaline injections resulted in mean Gis times of 16-2, 20-9 and 25-6 hr respectively. It was concluded that the Gis time depended on the recent history of cells with respect to stimulation, but not division. The results are considered in terms of two models, in one of which the time to leave Go is variable, whilst in the other the cells leave Go immediately the stimulus is applied.     

The accumulation of superoxide radical during the aerobic action of xanthine oxidase A requiem for H2O4−

The action of xanthine oxidase upon acetaldehyde or xanthine at pH 10.2 has been shown to be accompanied by substantial accumulation of O₂^? during the first few minutes of the reaction. H₂O₂ decreases this accumulation of O₂^? presumably because of the Haber-Weiss reaction ($\text{H}{}_2\text{O}{}_2\text{+}\text{O}{}_2{}^{\mathrm{?}}\text{→}\text{OH}{}^{\mathrm{?}}\text{+}\text{OH}\text{+}\text{O}{}_2$) and very small amounts of superoxide dismutase eliminate it. This accumulation of O₂^? was demonstrated in terms of a burst of reduction of cytochrome $\text{c}$, seen when the latter compound was added after aerobic preincubation of xanthine oxidase with its substrate. The kinetic peculiarities of the luminescence seen in the presence of luminol, which previously led to the proposal of H₂O₄^?, can now be satisfactorily explained entirely on the basis of known radical intermediates.     

The interaction of bovine erythrocyte superoxide dismutase with hydrogen peroxide: inactivation of the enzyme.

Bovine erythrocyte superoxide dismutase was slowly and irreversibly inactivated by hydrogen peroxide. The rate of this inactivation was directly dependent upon the concentrations of both H2O2 and of enzyme, and its second-order rate constant at pH 10.0 and 25 degrees was 6.7 M-1 sec-1. Inactivation was preceded by a bleaching due to rapid reduction of Cu2+ on the enzyme, and following this there was a gradual reappearance of a new absorption in the visible region, which was coincident with the loss of catalytic activity. Inactivation of the enzyme was pH-dependent and indicated an essential ionization whose pKa was approximately 10.2. Replacement of H2O by D2O raised this pKa but did not diminish the catalytic activity of superoxide dismutase, measured at pH 10.0. Several compounds, including xanthine, urate, formate, and azide, protected the enzyme against inactivation by H2O2. Alcohols and benzoate, which scavenge hydroxyl radical, did not protect. Compounds with special affinity for singlet oxygen were similarly ineffective. The data were interpreted in terms of the reduction of the enzyme-bound Cu2+ to Cu+, by H2O2, followed by a Fenton's type reaction of the Cu+ with additional H2O2. This would generate Cu2+-OH- or its ionized equivalent, Cu2+-O--, which could then oxidatively attack an adjacent histidine and thus inactivate the enzyme. Compounds which protected the enzyme could have done so by reacting with the bound oxidant, in competition with the adjacent histidine.     

Wading through the swamp: what does tropical peatland restoration mean to national‐level stakeholders in Indonesia?

Ecological restoration is considered to play an important role in mitigating climate change, protecting biodiversity, and preventing environmental degradation. Yet, there are often multiple perspectives on what outcomes restoration should be aiming to achieve, and how we should get to that point. In this study we interview a range of policymakers, academics, and non‐governmental organization (NGO) representatives to explore the range of perspectives on the restoration of Indonesia's tropical peatlands—key global ecosystems that have undergone large‐scale degradation. Thematic analysis suggests that participants agreed about the importance of restoration, but had differing opinions on how effective restoration activities to date have been and what a restored peatland landscape should look like. These results exemplify how ecological restoration can mean different things to different people, but also highlight important areas of consensus for moving forward with peatland restoration strategies.