Hydroubiquinone-cytochrome c2 oxidoreductase from Rhodobacter capsulatus: definition of a minimal, functional isolated preparation

The hydroubiquinone-cytochrome c2 oxidoreductase (cyt bc1) from Rhodobacter capsulatus has been solubilized according to the dodecyl maltoside method and isolated, and its minimal functional composition has been characterized. We find the complex to be composed of three protein subunits corresponding to polypeptides of cyt b (44 kDa), cyt c1 (33 kDa), and 2Fe2S cluster (24 kDa). A fourth band sometimes discernable at 22 kDa appears to be an artifact of the polyacrylamide gel electrophoresis procedure. Its appearance is shown to be derived from the 2Fe2S cluster subunit by the similarity of the binding of subunit-specific monoclonal antibodies and the identical N-terminal sequence of the 24- and 22-kDa bands. The cofactors of cyt bc1, namely, cyt bH, cyt bL, cyt c1, and the 2Fe2S center, the Qos and Qow domains of the Qo site, and the Qi site appear intact as indicated by their optical and EPR spectral signatures, redox properties, and inhibitor binding. The electron paramagnetic resonance spectrum of the cyt bH heme is altered by antimycin, consistent with a change in the dihedral angle between the ligating histidine imidazoles, while the spectrum of the cyt bL heme is broadened by stigmatellin. The ubiquinone-10 content is variable, ranging from 0.8 to 3 molecules/cyt bc1. Activity studies define this three-subunit cyt bc1 complex as a minimal structure, equipped as the enzyme in the native state and capable of full catalytic activity.

In vitro inhibitory effect of IL-8 and other chemoattractants on neutrophil-endothelial adhesive interactions

We have previously reported that cytokine- or LPS-activated human umbilical vein endothelial cell (HUVEC) monolayers secrete IL-8 that can act as a neutrophil-selective adhesion inhibitor. In our study we investigated the mechanisms involved in the leukocyte adhesion inhibitory action of IL-8. The leukocyte adhesion inhibitory effect appears to be mediated by the action of IL-8 on the neutrophil, does not involve down-regulation of relevant endothelial adhesion molecules such as endothelial-leukocyte adhesion molecule-1 or intercellular adhesion molecule-1, and is quantitatively similar in different endothelial activation states that are predominantly endothelial-leukocyte adhesion molecule-1 dependent or intercellular adhesion molecule-1 dependent. In addition to inhibiting the attachment of freshly isolated peripheral blood neutrophils to cytokine-activated HUVEC monolayers, IL-8 also promoted a rapid detachment of tightly adherent neutrophils from activated HUVEC, and abolished neutrophil transendothelial migration. Certain other chemoattractants, including FMLP and C5a, had similar inhibitory actions, indicating IL-8 was not unique in its ability to inhibit various neutrophil-endothelial interactions. In contrast, two other neutrophil agonists 1-0-alkyl-2-acetyl sn-glycero-3-phosphocholine and granulocyte-macrophage-CSF, which, like IL-8, are produced by activated HUVEC, as well as the leukocyte-derived chemoattractant leukotriene B4, exerted minimal inhibitory effects on adhesion. Regardless of their ability to modulate neutrophil-endothelial cell adhesion, all these agents induced altered leukocyte surface expression of functionally important adhesion molecules, including loss of L-selectin (leukocyte adhesion molecule-1, LECAM-1) and increase in CD11b/CD18. Thus, although the above agonists have been characterized primarily as chemoattractants, our findings demonstrate that these agents can exert a wide range of modulatory effects on neutrophil-endothelial adhesive interactions.

In vitro inhibitory effect of IL-8 and other chemoattractants on neutrophil-endothelial adhesive interactions

We have previously reported that cytokine- or LPS-activated human umbilical vein endothelial cell (HUVEC) monolayers secrete IL-8 that can act as a neutrophil-selective adhesion inhibitor. In our study we investigated the mechanisms involved in the leukocyte adhesion inhibitory action of IL-8. The leukocyte adhesion inhibitory effect appears to be mediated by the action of IL-8 on the neutrophil, does not involve down-regulation of relevant endothelial adhesion molecules such as endothelial-leukocyte adhesion molecule-1 or intercellular adhesion molecule-1, and is quantitatively similar in different endothelial activation states that are predominantly endothelial-leukocyte adhesion molecule-1 dependent or intercellular adhesion molecule-1 dependent. In addition to inhibiting the attachment of freshly isolated peripheral blood neutrophils to cytokine-activated HUVEC monolayers, IL-8 also promoted a rapid detachment of tightly adherent neutrophils from activated HUVEC, and abolished neutrophil transendothelial migration. Certain other chemoattractants, including FMLP and C5a, had similar inhibitory actions, indicating IL-8 was not unique in its ability to inhibit various neutrophil-endothelial interactions. In contrast, two other neutrophil agonists 1-0-alkyl-2-acetyl sn-glycero-3-phosphocholine and granulocyte-macrophage-CSF, which, like IL-8, are produced by activated HUVEC, as well as the leukocyte-derived chemoattractant leukotriene B4, exerted minimal inhibitory effects on adhesion. Regardless of their ability to modulate neutrophil-endothelial cell adhesion, all these agents induced altered leukocyte surface expression of functionally important adhesion molecules, including loss of L-selectin (leukocyte adhesion molecule-1, LECAM-1) and increase in CD11b/CD18. Thus, although the above agonists have been characterized primarily as chemoattractants, our findings demonstrate that these agents can exert a wide range of modulatory effects on neutrophil-endothelial adhesive interactions.

[Hepatic segmentectomy using microwave tissue coagulator]

Hepatic segmentectomy using a microwave tissue coagulator guided by intraoperative ultrasonography is a new operative procedure, which our research unit was the first to start using from 1990. Up to now we have performed this kind of operation with success in 26 cases. Our results suggested that the new procedure simplified the original operation and greatly reduced the risk of hemorrhage and iatrogenic spread of the cancer cells during operation. Besides, this operation as a kind of definite anatomic hepatectomy can minimally resect the tumor bearing tissue in a radical fashion, while maximally preserve the tumor-free tissue of the liver.

Evaluation of the API Coryne test system for identification of Actinomyces pyogenes

The present study was designed to evaluate the accuracy of the API Coryne test system for identification of Actinomyces pyogenes. The test system correctly identified 36 of 42 A. pyogenes and 4 of 5 comparatively studied Arcanobacterium haemolyticum-cultures. The biochemical profiles of the remaining 6 A. pyogenes- and 1 A. haemolyticum-cultures were not included in the analytical profile index. None of the cultures were misidentified. According to the API database (ATB Plus V 1.5.4.) the unidentified cultures could be correctly identified as A. pyogenes and A. haemolyticum respectively. A greater repertoire of A. pyogenes specific biochemical profiles incorporated into the analytical profile index would improve the applicability of this test system for veterinary diagnostics.

Cytochrome bc1 complex [2Fe-2S] cluster and its interaction with ubiquinone and ubihydroquinone at the Qo site: a double-occupancy Qo site model

The ubiquinone complement of Rhodobacter capsulatus chromatophore membranes has been characterized by its isooctane solvent extractability and electrochemistry; we find that the main ubiquinone pool (Qpool) amounts to about 80% of the total ubiquinone and has an Em7 value close to 90 mV. To investigate the interactions of ubiquinone with the cyt bc1 complex, we have examined the distinctive EPR line shapes of the [2Fe-2S] cluster of the cyt bc1 complex when the Qpool-cyt bc1 complex interactions are modulated by changing the numbers of Q or QH2 present (by solvent extraction and reconstitution), by the exposure of the [2Fe-2S] to the Qpool in different redox states, by the presence of inhibitors specific for the Qo site (myxothiazol and stigmatellin) and Qi site (antimycin), and by site-specific mutations of side chains of the cyt b polypeptide (mutants F144L and F144G) previously identified as important for Qo site structure. Evidence suggests that the Qo site can accommodate two ubiquinone molecules. One (designated Qos) is bound relatively strongly and is second only to the ubiquinone of the QA site of the reaction center in its resistance to solvent extraction. In this strong interaction, the Qo site binds Q and QH2 with approximately equal affinities. Their bound states are distinguished by their effects on the [2Fe-2S] cluster spectral feature at gx at 1.783 (Q) and gx at 1.777 (QH2); titration of the line-shape change reveals an Em7 value of approximately 95 mV. The other molecule (Qow) is bound more weakly, in the same range as the ubiquinone of the QB site of the reaction center. Again, the affinities of the Q form (gx at 1.800) and QH2 form (gx at 1.777) are nearly equal, and the Em7 value measured is approximately 80 mV. These results are discussed in terms of earlier EPR analyses of the cyt bc1 complexes of other systems. A Qo site double-occupancy model is considered that builds on the previous model based on Qo site mutants [Robertson, D. E., Daldal, F.,& Dutton, P. L. (1990) Biochemistry 29, 11249-11260] and includes the recent suggestion that two of the [2F3-2S] cluster ligands of the R. capsulatus cyt bc1 complex are histidines [Gurbiel, R. J. Ohnishi, T., Robertson, D. E. Daldal, F., & Hoffman, B. M. (1991) Biochemistry 30, 11579-11584]. We speculate that the cyt bc1 complex complexes a full enzymatic turnover without necessary exchange of ubiquinone with the Qpool.

Cell surface hydrophobicity of Actinomyces pyogenes determined by hexadecane adherence- and salt aggregation studies

Cell surface hydrophobicities of Actinomyces pyogenes were determined by measuring the adherence of the bacteria to hexadecane droplets and by salt aggregation tests. Among 42 A. pyogenes cultures tested 25 (60%) adhered strongly (adherence greater than or equal to 75%) and 17 (40%) less pronounced (adherence between 25-75%) to the hexadecane droplets. Pre-treatment of the bacteria with proteolytic enzymes completely eliminated the adherence properties whereas heat treatment had no effect. The salt aggregation studies revealed that 4 (10%) cultures aggregated in ammonium sulfate solutions of a molarity of 0.05 mol/l, 5 (12%), 14 (33%) and 3 (7%) cultures in ammonium sulfate solutions with molarities of greater than or equal to 1.5 mol/l, greater than or equal to 3 mol/l and greater than or equal to 4.5 mol/l, respectively. No aggregation at all could be observed with 16 (38%) of the cultures. Pronase treatment completely eliminated the salt aggregation reactions, trypsin- and heat treatment had no effect. The results from hexadecane adherence and salt aggregation did not correspond. The differences in surface hydrophobicities, possibly related to adherence properties of A. pyogenes, could be used for epidemiological typing of individual cultures of this bacterial species.

[Central norepinephrine and angiotensin II contents in the brain regions of spontaneously hypertensive rats (SHR) and the interaction between them]

The norepinephrine (NE) and angiotensin II (A II) contents in the brain regions of SHR and WKY (Wistar Kyoto) rats at different ages were determined by fluorospectrophotometry and radioimmunoassay. The systolic blood pressure (SBP) of the rats was measured indirectly with a tail cuff technique in conscious state. The results were as follows: There was no significant difference in the central A II and NE contents between SHR and WKY rats at 8-week age. Since 12th week age the SBP of SHR has increased gradually, up to 16th to 20th week and then maintained steady level. Whereas there was no significant change of SBP in WKY rats in the same span of age. In the early and late states of hypertension the A II contents in the medulla oblongata, pons, hypothalamus and nucleus caudatus of SHR were markedly higher than those of the age-matched WKY rats. But the change of NE content of SHR in the early stage showed a different picture as compared with that of WKY rats, i.e., NE decreased in medulla oblongata and anterior hypothalamus but increased in pons, posterior hypothalamus and nucleus caudatus. However, in the late stage there was no such significant difference between SHR and WKY rats. Consequently, it is suggested that the central A II and NE participated in the development of hypertension of SHR, and that the maintenance of hypertension is mainly dependent upon the increased A II content. Microinjection of captopril or 6-OHDA in the lateral cerebroventricle of SHR elicited a decrease of BP and reduction of both A II and NE contents in the medulla and hypothalamus.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of the overactivated central renin-angiotensin system on the concentration of brain norepinephrine and epinephrine in stroke-prone spontaneously hypertensive rats and its significances]

The content of norepinephrine (NE) and epinephrine (E) in the brain of spontaneously hypertensive rats has proved abnormal, but the cause remained unknown. It was shown in the recent work that NE content in pons, posterior hypothalamus, nucleus caudatus and E concentration in medulla oblongata, anterior and posterior hypothalamus of 12-week old stroke-prone spontaneously hypertensive rats (SHRSP) were much higher than those of age-matched Wister-Kyoto rats (WKY). SHRSP also showed higher levels of systolic blood pressure (SBP) and brain angiotensin II (A II) than WKY. Intracerebroventricular (icv) perfusion of angiotensin-converting enzyme inhibitor captopril (20 micrograms for each time and three times for each day for four weeks) inhibited the synthesis of brain A II and reduced SBP and NE, E contents in all examined brain areas in SHRSP and WKY. However, the effects of chronically perfused captopril on SBP and brain NE, E levels in SHRSP were much more significant than in WKY. The results indicate that the modulatory effects of central renin-angiotensin system (RAS) on central adrenergic and noradrenergic system might be overactivated in SHRSP, which might partially responsible for the abnormally high levels of NE, E in some of the brain areas of SHRSP.

[Preliminary studies on the relationship between the blood pressure and renin-angiotensin system in brain and blood vessels in SHRSP]

This work analyzed the relationship between A I concentration in aorta tissue and systolic blood pressure (SBP) in stroke-prone spontaneously hypertensive rats (SHRSP) at different ages. The SBP of SHRSP increased progressively with the age until the age of 20 weeks, when the SBP of SHRSP no longer elevated but sustained at a relatively high and stable level. The A I concentration in aorta of SHRSP was much higher than that of Wistar Kyoto rats at all of the three different ages. Perfusion of captopril into the lateral cerebroventricle of SHRSP for four weeks evoked a considerable decrease of A I concentration in brain as well as a significant reduction of SBP accompanied by a decrement of A I concentration in aorta and concentration of norepinephrine and epinephrine in aorta tissue and plasma. The results further confirm the close relationship between the changed activity of renin-angiotensin system localized in blood vessels during hypertension and the pathogenesis of hypertension, and indicate the possible regulative control of A I generated from central nervous system over the production of A I from blood vessels by means of facilitating the activity of peripheral sympathetic nerve system.

Analysis of the causes of maternal death in China

Data were analysed on maternal mortality for 1984 in 287 cities, districts, and counties in 21 provinces, municipalities, and autonomous regions of China. The total population covered was 177.55 million, and during the study period there were 2 483 269 live births and 1211 maternal deaths, corresponding to a maternal mortality rate of 48.8 per 100 000. The main cause of maternal death was obstetric haemorrhage, followed, in order, by cardiac diseases, toxaemia of pregnancy, hepatic disease, puerperal infection, and amniotic fluid embolism. The health care measures received by the mothers who died are analysed, and methods of reducing the maternal mortality rate are proposed.