Mechanisms compensating for altered resistance to respiration during muscular exercise in man

Alterations in respiratory parameters following the substitution of a helium-oxygen (He−O₂) or sulfur hexafluoride-oxygen (SF₆−O₂) mixture for air were analyzed during the first 10 respiratory cycles in human volunteers exposed to either of these mixtures for 3 min at rest and during forced respiration. Both at rest and during moderate physical exercise neither the volume of pulrnonary ventilation nor the partial carbon dioxide pressure differed significantly in the subjects breathing air, He−O₂, or SF₆−O₂. When the He−O₂ mixture was substituted for air, the forces developed by the inspiratory muscles, the work of breathing, the activity of the parasternal intercostal muscles, and the central inspiratory activity were all reduced, whereas substitution of the SF₆−O₂ mixture for air led to significant increases in these four parameters. It is concluded that compensatory responses of the respiratory system to altered density of the gaseous medium develop on the basis of the afferent impulse traffic from mechanoreceptors of the lungs and respiratory muscles and also on account of segmental reflexes and intrinsic properties of the muscle fibers themselves. Translated fromByulleten' Eksperimental'noi Biologii i Meditsiny, Vol. 120, N ^o 9, pp. 247–251, September, 1995 Presented by A. D. Ado, Member of the Russian Academy of Medical Sciences     

Midregional proadrenomedullin reflects cardiac dysfunction in haemodialysis patients with cardiovascular disease.

BACKGROUND: Although adrenomedullin is an indicator of cardiac dysfunction in haemodialysis patients, the clinical significance of midregional proadrenomedullin has not been elucidated. Objectives. We evaluated whether midregional proadrenomedullin reflects cardiac dysfunction, systemic inflammation or blood volume in haemodialysis patients. METHODS: Plasma midregional proadrenomedullin, C-reactive protein and delta body weight (indicating excessive blood volume), and two-dimensional as well as Doppler echocardiographic variables were measured just before haemodialysis in 70 patients with cardiovascular disease. RESULTS: The median value of midregional proadrenomedullin was 1.93 nmol/l before haemodialysis, and these levels were significantly reduced following haemodialysis. Log [midregional proadrenomedullin] was positively correlated with left ventricular end-systolic volume index, diameter of inferior vena cava, C-reactive protein and delta body weight (r = 0.328, r = 0.421, r = 0.356, r = 0.364), and negatively with blood pressure, deceleration time of an early diastolic filling wave, pulmonary venous flow velocity ratio and left ventricular ejection fraction (r = -0.330, r = -0.324, r = -0.479, r = -0.373). Multivariate regression analysis revealed that pulmonary venous flow velocity ratio, diameter of inferior vena cava and C-reactive protein were independently related factors for midregional proadrenomedullin concentration. CONCLUSION: Plasma midregional proadrenomedullin levels increase in association with cardiac dysfunction, systemic inflammatory status and systemic blood volume in haemodialysis patients with concomitant cardiovascular disease.     

胃溃疡胃实寒,实热证模型大鼠经穴辐射热,pH值,氧分压的检测研究

采用醋酸法造成大鼠胃溃疡，施加寒、热病因刺激，造成实寒、实热证胃溃疡大鼠模型。对模型大鼠穴区辐射热、ｐＨ值、氧分压进行检测研究，结果提示：溃疡大鼠相关穴区信息均有异常改变，与肺经穴比较，差异有显著性意义（Ｐ＜０．０５），且变化规律具有与寒热病性相关的特点，揭示了经穴与内脏相关关系的某些规律     

新肤螨灵霜治疗酒渣鼻

应用新肤螨灵霜和5％硫磺霜双盲对照试验治疗酒渣鼻64例(男23,女41,年龄40±12a),43例应用新肤螨灵霜,21例应用5％硫磺霜,1月2次,疗程14-20d。新肤螨灵霜的临床治愈率14％,显效49％,有效28％,总有效率91％,明显优于5％硫磺箱(P<0.01)。副作用较轻。因此,新肤螨灵霜值得在临床上试用。     

EFNS guidelines on management of narcolepsy

Management of narcolepsy with or without cataplexy relies on several classes of drugs, namely stimulants for excessive daytime sleepiness and irresistible episodes of sleep, antidepressants for cataplexy and hypnosedative drugs for disturbed nocturnal sleep. In addition, behavioral measures can be of notable value. Guidelines on the management of narcolepsy have already been published. However contemporary guidelines are necessary given the growing use of modafinil to treat excessive daytime sleepiness in Europe within the last 5–10 years, and the decreasing need for amphetamines and amphetamine‐like stimulants; the extensive use of new antidepressants in the treatment of cataplexy, apart from consistent randomized placebo‐controlled clinical trials; and the present re‐emergence of gamma‐hydroxybutyrate under the name sodium oxybate, as a treatment of all major symptoms of narcolepsy. A task force composed of the leading specialists of narcolepsy in Europe has been appointed. This task force conducted an extensive review of pharmacological and behavioral trials available in the literature. All trials were analyzed according to their class evidence. Recommendations concerning the treatment of each single symptom of narcolepsy as well as general recommendations were made. Modafinil is the first‐line pharmacological treatment of excessive daytime sleepiness and irresistible episodes of sleep in association with behavioral measures. However, based on several large randomized controlled trials showing the activity of sodium oxybate, not only on cataplexy but also on excessive daytime sleepiness and irresistible episodes of sleep, there is a growing practice in the USA to use it for the later indications. Given the availability of modafinil and methylphenidate, and the forseen registration of sodium oxybate for narcolepsy (including excessive daytime sleepiness, cataplexy, disturbed nocturnal sleep) in Europe, the place of other compounds will become fairly limited. Since its recent registration cataplexy sodium oxybate has now become the first‐line treatment of cataplexy. Second‐line treatments are antidepressants, either tricyclics or newer antidepressants, the later being increasingly used these past years despite few or no randomized placebo‐controlled clinical trials. As for disturbed nocturnal sleep the best option is still hypnotics until sodium oxybate is registered for narcolepsy. The treatments used for narcolepsy, either pharmacological or behavioral, are diverse. However the quality of the published clinical evidences supporting them varies widely and studies comparing the efficacy of different substances are lacking. Several treatments are used on an empirical basis, specially antidepressants for cataplexy, due to the fact that these medications are already used widely in depressed patients, leaving little motivation from the manufacturers to investigate efficacy in relatively rare indications. Others, in particular the more recently developed substances, such as modafinil or sodium oxybate, are evaluated in large randomized placebo‐controlled trials. Our objective was to reinforce the use of those drugs evaluated in randomized placebo‐controlled trials and to reach a consensus, as much as possible, on the use of other available medications.     

防酸隔爆式消氢装置的研究

本文根据劳动卫生和环境保护的要求,对电力、邮电、化工等部门用作备用电源的铅蓄电池采取防酸、隔爆、消氢措施,并研制成实用装置,效果较好。文中叙述了该装置的工作原理及主要试验结果。     

Occurrence,integrity and functionality of AcaML1–like viruses infecting extreme acidophiles of the Acidithiobacillus species complex

General knowledge on the diversity and biology of microbial viruses infecting bacterial hosts from extreme acidic environments lags behind most other econiches. In this study, we analyse the AcaML1 virus occurrence in the taxon, its genetic composition and infective behaviour under standard acidic and SOS-inducing conditions to assess its integrity and functionality. Occurrence analysis in sequenced acidithiobacilli showed that AcaML1-like proviruses are confined to the mesothermophiles Acidithiobacillus caldus and Thermithiobacillus tepidarius. Among A. caldus strains and isolates this provirus had a modest prevalence (30%). Comparative genomic analysis revealed a significant conservation with the T. tepidarius AcaML1-like provirus, excepting the tail genes, and a high conservation of the virus across strains of the A. caldus species. Such conservation extends from the modules architecture to the gene level, suggesting that organization and composition of these viruses are preserved for functional reasons. Accordingly, the AcaML1 proviruses were demonstrated to excise from their host genomes under DNA-damaging conditions triggering the SOS-response and to produce DNA-containing VLPs. Despite this fact, under the conditions evaluated (acidic) the VLPs obtained from A. caldus ATCC 51756 could not produce productive infections of a candidate sensitive strain (#6) nor trigger it lysis.     

Effect of cinnamon (Cinnamomum verum) bark essential oil on the halitosis-associated bacterium Solobacterium moorei and in vitro cytotoxicity

ObjectivesHalitosis, also known as bad breath or oral malodour, is a condition affecting a large proportion of the population. Solobacterium moorei is a Gram-positive anaerobic bacterium that has been specifically associated with halitosis. In this study, we investigated the effects of essential oils, more particularly cinnamon bark oil, on growth, biofilm formation, eradication and killing, as well as hydrogen sulfide (H₂S) production by S. moorei.MethodsA broth microdilution assay was used to determine the antibacterial activity of essential oils. Biofilm formation was assessed by a crystal violet staining assay and scanning electron microscopy. The biofilm of S. moorei was characterized by enzymatic treatments. Biofilm killing was determined by a luminescence assay monitoring ATP production. H₂S production was quantified with a colorimetric assay. The biocompatibility of cinnamon oil was investigated using a gingival keratinocyte cell line.ResultsAmong the ten essential oils tested, cinnamon oil was found to be the most powerful against S. moorei with MIC and MBC values of 0.039% and 0.156%, respectively. The biofilm formed by S. moorei was then characterized. The fact that DNase I and to a lesser extent proteinase K significantly reduced biofilm formation by S. moorei and induced its eradication suggests that the extracellular matrix of S. moorei biofilm may be mainly containing a DNA backbone associated with proteins. At concentrations below the MIC, cinnamon oil reduced S. moorei biofilm formation that resulted from an attenuation of bacterial growth. It was also found that treatment of a pre-formed biofilm of S. moorei with cinnamon oil significantly decreased its viability although it did not cause its eradication. Cinnamon oil had an inhibitory effect on the production of H₂S by S. moorei. Lastly, it was found that at concentrations effective against S. moorei, no significant loss of viability in gingival keratinocytes occurred after a 1-h exposure.ConclusionsOur study brought evidence that cinnamon oil may be a promising substance to incorporate into oral hygiene products for controlling bad breath by inhibiting growth, killing biofilm, and reducing H₂S production by S. moorei. Moreover, at the effective concentrations, cinnamon oil was found to have no toxic effects on oral keratinocytes.     

From the Cover: Leinamycin E1 acting as an anticancer prodrug activated by reactive oxygen species

Leinamycin (LNM) is a potent antitumor antibiotic produced by Streptomyces atroolivaceus S-140, featuring an unusual 1,3-dioxo-1,2-dithiolane moiety that is spiro-fused to a thiazole-containing 18-membered lactam ring. Upon reductive activation in the presence of cellular thiols, LNM exerts its antitumor activity by an episulfonium ion-mediated DNA alkylation. Previously, we have cloned the lnm gene cluster from S. atroolivaceus S-140 and characterized the biosynthetic machinery responsible for the 18-membered lactam backbone and the alkyl branch at C3 of LNM. We now report the isolation and characterization of leinamycin E1 (LNM E1) from S. atroolivacues SB3033, a ΔlnmE mutant strain of S. atroolivaceus S-140. Complementary to the reductive activation of LNM by cellular thiols, LNM E1 can be oxidatively activated by cellular reactive oxygen species (ROS) to generate a similar episulfonium ion intermediate, thereby alkylating DNA and leading to eventual cell death. The feasibility of exploiting LNM E1 as an anticancer prodrug activated by ROS was demonstrated in two prostate cancer cell lines, LNCaP and DU-145. Because many cancer cells are under higher cellular oxidative stress with increased levels of ROS than normal cells, these findings support the idea of exploiting ROS as a means to target cancer cells and highlight LNM E1 as a novel lead for the development of anticancer prodrugs activated by ROS. The structure of LNM E1 also reveals critical new insights into LNM biosynthesis, setting the stage to investigate sulfur incorporation, as well as the tailoring steps that convert the nascent hybrid peptide–polyketide biosynthetic intermediate into LNM.Leinamycin (LNM) (Fig. 1A, 1) is an antitumor antibiotic produced by Streptomyces atroolivaceus S-140 (1). It features an unusual 1,3-dioxo-1,2-dithiolane moiety that is spiro-fused to a thiazole-containing 18-membered lactam ring, a molecular architecture not found to date in any other natural product (Fig. 1A). LNM shows potent antitumor activity in vitro and in vivo and is active against tumors that are resistant to clinically important anticancer drugs, such as cisplatin, doxorubicin, mitomycin, and cyclophosphamide; therefore 1 has been pursued as a promising anticancer drug lead (2–4).Open in a separate windowFig. 1.LNM (1) and LNM E1 (2) as novel anticancer drug leads via episulfonium ion-mediated DNA alkylation upon complementary activation: (A) reductive activation of 1 by cellular thiols and (B) oxidative activation of 2 by cellular ROS, affording a pair of episulfonium ions that efficiently alkylate the N7 position of deoxyguanosine bases of DNA, thereby causing DNA cleavage and eventual cell death.The mode of action of 1 has been extensively investigated. The 1,3-dioxo-1,2-dithiolane moiety of 1 is essential for its antitumor activity. Upon reductive activation in the presence of thiol agents, 1 exerts its antitumor activity by an episulfonium ion-mediated DNA alkylation, a mode of action that is unprecedented among all DNA-damaging natural products (Fig. 1A). Thus, under a reductive cellular environment, the 1,3-dioxo-1,2-dithiolane moiety of 1 is first attacked by a thiol to produce a sulfenic acid intermediate (1a) that can cyclize, by ejecting a persulfide, to form a 1,2-oxathiolan-5-one intermediate (1b). Subsequent rearrangement of 1b, through an intramolecular attack of the 1,2-oxathiolan-5-one moiety by the C-6/C-7 alkene, affords an episulfonium ion intermediate (1c), which can efficiently alkylate the N7 position of deoxyguanosine bases of DNA (1d), ultimately causing DNA cleavage and cell death. The episulfonium ion 1c exists in equilibrium with an epoxide 1e through the intramolecular backside attack by the C-8-hydroxyl group (Fig. 1A) (4–11). Although 1c formation does not require DNA, because the hydrolysis product (1f) forms rapidly in the absence of DNA (5), noncovalent DNA binding by the Z,E-5-(thiazol-4-yl)-penta-2,4-dienone moiety of 1 significantly enhances its DNA alkylation activity (9). In addition, the persulfides generated in the formation of 1b also contribute to the observed DNA damaging activity of 1, but via an independent mechanism mediated by reactive oxygen species (ROS) (4, 12–14).We have previously cloned and sequenced the lnm biosynthetic gene cluster from S. atroolivaceus S-140, which consists of 27 ORFs (orfs) (15–17). In vivo and in vitro characterizations of the 1 biosynthetic machinery have since established that (i) the thiazole-containing 18-membered lactam backbone of 1 is synthesized by a hybrid nonribosomal peptide synthetase (NRPS)-acyltransferase (AT)–less type I polyketide synthase (PKS), consisting of LnmQ (adenylation protein), LnmP [peptidyl carrier protein (PCP)], LnmI (a hybrid NRPS-AT–less type I PKS), LnmJ (AT-less type I PKS), and LnmG (AT) (17–19) and (ii) the alkyl branch at C-3 of 1 is installed by a novel pathway for β-alkylation in polyketide biosynthesis, featuring LnmK (acyltransferase/decarboxylase), LnmL [acyl carrier protein (ACP)], LnmM [hydroxymethylglutaryl-CoA synthase (HCS)], and LnmF [enoyl-CoA hydratase (ECH)] (Fig. 2) (20–22). However, the mechanism of sulfur incorporation to form the 1,3-dioxo-1,2-dithiolane moiety, which is essential for the DNA damage activity of 1, as well as the tailoring steps that convert the nascent hybrid peptide–polyketide intermediate into 1, remains elusive.Open in a separate windowFig. 2.Proposed biosynthetic pathway for LNM (1) featuring (i) the LnmQPIJ hybrid NRPS-AT–less type I PKS with the discrete LnmG AT loading the malonyl CoA extender units to all six PKS modules, (ii) the LnmKLMF enzymes catalyzing the β-alkyl branch at C3, and (iii) LNM E1 (2) as a key intermediate for 1 biosynthesis, setting the stage to investigate the mechanism of sulfur incorporation and the tailoring steps that convert 2 to 1, requiring minimally hydroxylations at C-8 and C-4′, oxidation at S-1′, S-insertion at 2′, and 1,3-dioxo-1,2-dithiolane ring formation. Color coding indicates the moieties installed by NRPS (blue), PKS (red), β-alkyl branch (green), and other tailoring enzymes (black). SAM, S-adenosylmethionine. The green oval denotes an AT docking domain. Domain abbreviations are: A, adenylation; AT, acyltransferase; Cy, cyclization; DH, dehydratase; KR, ketoreductase; KS, ketosynthase; MT, methyltransferase, Ox, oxidation; PCP, peptidyl carrier protein; TE, thioesterase; ?, domain of unknown function.To shed light into these steps, we systematically inactivated all genes within the lnm cluster whose functions or roles in 1 biosynthesis cannot be readily predicted on the basis of bioinformatics analysis alone (16, 17). Each of the mutant strains was then fermented, with the S. atroolivaceus S-140 WT as a control, to isolate new metabolites accumulated to account for their roles in 1 biosynthesis. Here, we report the isolation and characterization of leinamycin E1 (LNM E1, 2) from SB3033, a ΔlnmE mutant strain of S. atroolivaceus S-140. Significantly, the structure of 2 reveals critical new insights into 1 biosynthesis, setting the stage to investigate sulfur incorporation, as well as the tailoring steps that convert the nascent hybrid peptide–polyketide biosynthetic intermediate into 1 (Fig. 2). Most strikingly, 2 can be readily oxidized into a sulfenic acid intermediate (2a), which, in a mechanistic analogy to 1a and via a similar 1,2-oxathiolan-5-one intermediate (2b) to 1b, can undergo further rearrangement to form an episulfonium ion intermediate (2c). Thus, complementary to the reductive activation of 1 by cellular thiols to generate an episulfonium ion intermediate, 2 can be oxidatively activated by cellular ROS to generate a similar episulfonium ion intermediate, thereby alkylating DNA and leading to eventual cell death (Fig. 1B). The feasibility of exploiting 2 as an anticancer prodrug activated by ROS was demonstrated in two prostate cancer cell lines, LNCaP and DU-145, that are known to exist under higher oxidative stress than normal tissues. Because many cancer cells are under higher cellular oxidative stress with increased levels of ROS than normal cells (23, 24), our results suggest a means of exploiting ROS to target cancer cells and highlight 2 as a novel lead for the development of anticancer prodrugs activated by ROS.