Value of pelvic ultrasound combined with pituitary MRI in diagnosis of central precocious puberty in girls

OBJECTIVE

This study aimed to investigate the value of pelvic ultrasound combined with pituitary magnetic resonance imaging (MRI) based on an artificial intelligence algorithm in the diagnosis of girls with central precocious puberty (CPP), providing reference for the prevention and control of CPP in girls.

PATIENTS AND METHODS

75 girls with CPP and 75 normal girls in Nantong First People's Hospital were studied. Pelvic ultrasound parameters were compared between the two groups based on an artificial intelligence algorithm. Pituitary MRI parameters were analyzed, and pituitary function parameters were explored.

RESULTS

The results showed that the diagnostic sensitivity, specificity, and accuracy of the convolutional neural network (CNN) algorithm were 72.3%, 74.6%, and 78.3%, respectively. The sensitivity, specificity, and accuracy of CNN algorithm were significantly higher (p<0.05). The long diameter, anteroposterior diameter, and transverse diameter of the uterus in the precocious puberty (PP) group were significantly larger than those in the normal group (NG). The ovarian long diameter, ovarian anteroposterior diameter, and ovarian transverse diameter in PP group were significantly larger than those in NG. Uterine volume and ovarian volume in PP group were clearly higher than those in NG. The largest follicle diameter was clearly larger in PP patients than in NG patients. The coronal height, coronal width, sagittal height, and sagittal anteroposterior diameter of PP group were clearly higher than those of NG (p<0.05). The sagittal cross-sectional area of pituitary MRI morphology in PP group was significantly greater than that in NG. The pituitary MRI morphology pituitary volume was 272.68 mm in PP group and 191.37 mm in NG, and the pituitary volume was clearly larger in PP group than in NG. The pituitary function parameters estradiol (E2), luteinizing hormone (LH) peak, follicle-stimulating hormone (FSH) peak, and LH peak/FSH peak were greater in PP group than in NG.

CONCLUSIONS

In summary, the uterine size and ovarian size of girls and the pituitary function index in PP group were larger. Pelvic ultrasound and pituitary MRI indexes can better diagnose CPP and can be widely used in clinical practice with positive diagnostic value.

[Survival analysis of unexpected small cell lung cancer following surgery]

Objective: To investigate the survival and influencing factors of unexpected small cell lung cancer following surgery. Methods: We respectively reviewed the clinical characters of 104 patients who underwent surgical treatment and be proved as small cell lung cancer by pathology between January 2000 to October 2020 in Chinese PLA General Hospital. Overall survival (OS) of patients was evaluated using Kaplan-Meier and Cox proportional hazards analysis. Results: Of 104 patients, 27 cases showed central lesions, and other 77 showed peripheral nodules. The margin of nodules was smooth in 42 cases on CT imaging. The median OS was 34.3 months and 5-year OS rate was 45.8%. Postoperative 5-year OS rates for patients were 52.1%, 45.4%, and 27.8% for clinical stages Ⅰ, Ⅱ, and Ⅲ, respectively. Univariate analyses identified the age, surgical access, surgical approach, N stage, TNM stage and vascular cancer emboli were associated with OS (P<0.05). The N stage was an independent factor for the OS of patients (P<0.05). Conclusions: Patients with unexpected SCLC, including Ⅰ, Ⅱ and part ⅢA stage have favorable outcome and can benefit from surgery and systemic postoperative treatment. Standard lobectomy plus systemic lymph node dissection is commended.

[Analysis of characteristics and trends of randomized controlled trials of gastric cancer between 2000 and 2019]

Objectives: To analyze the current development status of gastric cancer (GC) randomized controlled trials (RCT) between 2000 and 2019, and to review the basic characteristics of published RCT. Methods: ClinicalTrials.gov was searched for phase 3 or 4 RCT conducted between January 2000 and December 2019 with the keyword "gastric cancer", and the development trend of different types of RCT during different time periods was described. Basic features of registered RCT such as intervention, study area, single-center or multicenter, sample size, and funding were presented. PubMed and Scopus databases were searched to judge the publication status of studies completed until June 2016. The adequacy of the report was estimated by the Consolidated Standards of Reporting Trials (CONSORT) checklist. Design flaws were evaluated by Cochrane tool and/or whether a systematic literature review was cited. The data was analyzed by χ2 test or Fisher exact test. Results: There were 262 RCT including in the present study. The number of GC-RCT registered on ClinicalTrials.gov had been on the rise from 1 case in 2000 to 30 cases in 2015. The proportion of RCT associated with targeted therapy or immunotherapy increased from 0 during 2000-2004 to 37.1% (36/97) during2015-2019. The RCT registered in Asia was 191 cases, while that in non-Asia region was 71 cases. The proportion of multi-center RCT from non-Asia was higher than that from Asia (70.4% (50/71) vs. 50.3% (96/191), χ²=8.527, P=0.003). The proportion of RCT published was 59.1% (81/137). Among the published RCT, 65 (80.2%) studies were reported adequately, but 63 (77.8%) studies had avoidable design limitations. Conclusions: Targeted therapy and immunotherapy have become research hotspots in the treatment of GC. At present, there are inadequate multicenter RCT in Asia, and the publication rate of RCT is low. A considerable number of published RCT are reported inadequately and have avoidable design flaws.

[Analysis of characteristics and trends of randomized controlled trials of gastric cancer between 2000 and 2019]

Objectives: To analyze the current development status of gastric cancer (GC) randomized controlled trials (RCT) between 2000 and 2019, and to review the basic characteristics of published RCT. Methods: ClinicalTrials.gov was searched for phase 3 or 4 RCT conducted between January 2000 and December 2019 with the keyword "gastric cancer", and the development trend of different types of RCT during different time periods was described. Basic features of registered RCT such as intervention, study area, single-center or multicenter, sample size, and funding were presented. PubMed and Scopus databases were searched to judge the publication status of studies completed until June 2016. The adequacy of the report was estimated by the Consolidated Standards of Reporting Trials (CONSORT) checklist. Design flaws were evaluated by Cochrane tool and/or whether a systematic literature review was cited. The data was analyzed by χ² test or Fisher exact test. Results: There were 262 RCT including in the present study. The number of GC-RCT registered on ClinicalTrials.gov had been on the rise from 1 case in 2000 to 30 cases in 2015. The proportion of RCT associated with targeted therapy or immunotherapy increased from 0 during 2000-2004 to 37.1% (36/97) during 2015-2019. The RCT registered in Asia was 191 cases, while that in non-Asia region was 71 cases. The proportion of multi-center RCT from non-Asia was higher than that from Asia (70.4% (50/71) vs. 50.3% (96/191), χ²=8.527, P=0.003). The proportion of RCT published was 59.1% (81/137). Among the published RCT, 65 (80.2%) studies were reported adequately, but 63 (77.8%) studies had avoidable design limitations. Conclusions: Targeted therapy and immunotherapy have become research hotspots in the treatment of GC. At present, there are inadequate multicenter RCT in Asia, and the publication rate of RCT is low. A considerable number of published RCT are reported inadequately and have avoidable design flaws.

[Research progress on the correlation between small dense low-density lipoprotein-cholesterol and atherosclerotic cardiovascular disease]

Atherosclerotic cardiovascular disease (ASCVD), a series of cardiovascular diseases based on atherosclerosis, has attracted more clinical attention. However, with the increase of population-based research results, the diagnostic value of traditional blood lipid parameters such as low density lipoprotein-cholesterol (LDL-C) is showing limitations. In recent years, a large number of studies have confirmed that small dense low-density lipoprotein cholesterol (sdLDL-C) has lower affinity with low-density lipoprotein receptor, longer circulation time and easier to penetrate arterial endothelium, so it has stronger atherogenic effect. Therefore, we summarize the common detection methods of sdLDL-C, the research progress of the correlation between sdLDL-C and ASCVD risk, as well as the intervention measures and influencing factors of sdLDL-C level, in order to deepen the clinician's understanding of the role of sdLDL-C in ASCVD and achieve the early prevention, early detection and early diagnosis of chronic atherosclerosis.

[Predicting response to non-small cell lung cancer immunotherapy using pre-treatment contrast-enhanced CT texture-based classification]

Objective: To explore the value of pre-treatment contrast-enhanced computed tomography (CT)-based texture analysis in predicting response to non-small cell lung cancer (NSCLC) immunotherapy. Methods: From January to July 2018, a total of 51 lesions from 42 patients with advanced non-small cell lung cancer receiving immunotherapy at Shanghai Chest Hospital were selected in this retrospective study. Pre-treatment contrast-enhanced CT-based texture features were extracted by MaZda software. Ten optimal texture features were chosen based on three different methods: Fisher coefficient, mutual information measure (MI) and minimization of classification error probability combined average correlation coefficients(POE+ ACC), respectively. According to the efficacy of the first immunotherapy, 51 lesions were divided into non-progressive disease (non-PD, n=26) and progressive disease (PD, n=25). The differences were tested in each texture feature set between the two groups. The immunotherapy effects of target lesions were analyzed by principal component analysis(PCA), linear discriminant analysis (LDA) and nonlinear discriminant analysis (NDA). The sensitivity, specificity, accuracy, positive-predictive value (PPV) and negative-predictive value (NPV) were calculated. The area under the curve (AUC) was used to quantify the predictive accuracy of the three analysis models for each texture feature set and compare them with the actual classification results. Results: In all of three texture feature sets, the texture parameter differences of Perc.50%, Perc.90%, "S(5, 5)SumEntrp" and "S(4, 4)SumEntrp" were higher in PD group than those in non-PD group (all P<0.05). The classification result of texture feature set chosen by POE+ ACC and analyzed by NDA was identified as the best model (AUC=0.802, 95%CI: 0.674-0.930), and its sensitivity, specificity, accuracy, PPV and NPV were 72%, 88.5%, 80.4%, 85.7%, 76.7%, respectively. Conclusion: Pre-treatment contrast-enhanced CT-based texture characteristics of NSCLC may function as non-invasive biomarkers for the evaluation of response to immunotherapy.

Performance of BAC for DBPs precursors' removal for one year with micro-polluted lake water in East-China

Effectiveness of biological activated carbon (BAC) filter in removing disinfection byproducts (DBPs) precursors of micro-polluted lake water for one year was conducted. The formation potential (FP) of DBPs (trihalomethanes (THMs), haloacetic acids (HAAs) and Nitrosamines (NAs)), dissolved organic carbon (DOC), molecular weight (MW) distribution and excitation emission matrix fluorescence (EEM) of dissolved organic material (DOM) in the influent and effluent of BAC were determined. The results indicated that the removal efficiency (RE) of DOC ranged from 42.9-28.3%. Neither virgin GAC nor long-term operated BAC could efficiently dispose of THMs and HAAs precursors (RE from 35.2-18.8%, from 42 to 8.4%, respectively), however, BAC still showed good ability in removal of NAs precursors after a year operation, of which RE just dropped from 81.7-69.6%. There was strong correlation between RE of NAs precursors and DOC with small MW (<0.5 kDa). The removal of HAAs precursors showed relatively close relation to aromatic protein-like components and soluble microbial pollutants (SMPs). Weak direct relationship was found between the water quality parameters and THMs precursors.

[Analysis of clinicopathological features of clear cell tumor of the lung]

Objective: To analyze the clinicopathological features of clear cell tumor of the lung (CCTL). Methods: A total of 9 cases were collected from August 2008 to August 2019 in the Department of Pathology of the First Medical Center of PLA General Hospital and Hainan Hospital of PLA General Hospital. Their clinical data, pathological characteristics, immunohistochemical staining and special staining results were summarized and analyzed. Results: There were 3 males and 6 females, aged from 28 to 70 years (average 52.2 years). All tumors were located in the peripheral part of the lung, and were solitary in 8 cases, and multiple (24 nodules) in 1 case. The lesion was round or oval, with clear boundary. The diameter of the nodule was 0.5-5.5 cm. Histologically, the tumor cells were oval, short fusiform or polygonal, with obvious nucleoli. The tumor cells were mostly distributed in sheet around thin-walled vessels, and there was hyaline degeneration around the blood vessels. Neither necrosis nor mitosis could be seen. Immunohistochemical staining showed tumor cells were diffusely positive for Vimentin, and CD34, Melan-A, specific monoclonal antibody against melanoma (HMB45) and S-100 were positive with different degrees. Broad spectrum cytokeratin (CK), epithelial membrane antigen (EMA), smooth muscle actin (SMA), desmin, CD10, paired box gene 8 (PAX-8) or myomodulatory protein (Myo-D1) were all negative. The positive index of the proliferating cell nuclear antigen (Ki-67) was low. Schiff dyeing with periodate (PAS) staining was positive, PAS staining of glycogen digested by amylase (d-PAS) staining was negative. All the tumors in the nine cases were resected and patients were followed up for 5-137 months. Except 1 case was lost for follow-up, the other 8 cases survived without recurrence or metastasis of the disease. Conclusions: CCTL is a rare benign tumor, most of which are single, few of which can be multiple; histopathological characteristics and immunohistochemical staining are helpful for diagnosis and differentiated diagnosis. After complete resection, the prognosis was good. However, when histological features indicating malignancy, intense follow-up should be considered.

[Role and potential value of circular RNAs in the occurrence of primary hepatic cancer]

Circular RNA is a class of non-coding RNAs, which are covalently closed and circular at both ends, showing dissimilar characteristics from linear RNA. Several studies have shown that circular RNAs play an important role in the occurrence and development of primary hepatic cancer. By combining with the latest research progress of this field at home and abroad, we summarized the mechanism regulating the occurrence and development of liver cancer, abnormal expression, and as potential molecular markers for disease diagnosis and treatment.

Glutathione S-transferase P1 rs1695 A>G polymorphism and breast cancer risk: evidence from a meta-analysis

Breast cancer (BC) is the most widespread cause of cancer-related deaths in women. Many published studies have assessed the association between the glutathione S-transferase P1 (GSTP1) rs1695 polymorphism and BC risk. However, the effect of the GSTP1 rs1695 polymorphism on BC risk has remained controversial. Therefore, this meta-analysis was conducted to obtain a comprehensive estimation of this association. A total of 20,615 cases and 20,481 controls from thirty-six case-control trials were extracted from an online literature survey. The meta-analysis indicated that the GSTP1 rs1695 A>G polymorphism did not contribute to the susceptibility of BC when the overall population was considered. However, intriguingly, this polymorphism was significantly associated with increased risk of BC in Asian women [GG vs AA: odds ratio (OR) = 1.4, 95% confidence interval (CI): 1.06-1.88, P = 0.02; AG vs AA: OR = 1.08, 95%CI = 1.00-1.16, P = 0.05; GG/AG vs AA: OR = 1.11, 95%CI = 1.04-1.19, P = 0.00]. Moreover, a subgroup analysis based on the source of control groups showed a marked increase in BC susceptibility in hospital-based control subjects (GG vs AA: OR = 1.28, 95%CI = 1.10-1.48, P= 0.00; GG vs

AG/AA

OR = 1.22, 95%CI = 1.06-1.41, P = 0.00; GG/AG vs AA: OR = 1.10, 95%CI = 1.02-1.18, P = 0.00). In conclusion, our study indicated that the GSTP1 rs1695 A>G polymorphism was correlated with elevated BC risk in Asian women. Our results must be validated with further research.

Implicating the H63D polymorphism in the HFE gene in increased incidence of solid cancers: a meta-analysis

A number of previous studies have demonstrated that the HFE H63D polymorphism is associated with increased risk of incidence multiple types of cancer, including colorectal cancer, breast cancer, liver cancer, pancreatic cancer, and gynecological malignant tumors. However, the clinical outcomes were inconsistent. Therefore, this meta-analysis was conducted to summarize the effect of the H63D variant on the incidence of solid tumor. PubMed and EMBASE databases were searched for articles associating the HFE H63D polymorphism with cancer risk. The relationships were evaluated by calculating the pooled odds ratios (ORs) with 95% confidence intervals (CIs). A total of 28 studies, including 7728 cancer cases and 11,895 controls, were identified. Statistically significant associations were identified between the HFE H63D polymorphism and solid cancer risk (CG vs CC, OR = 1.14, 95%CI = 1.07-1.23, P < 0.001; GG vs CC, OR = 1.28, 95%CI = 1.06-1.55, P = 0.010; CG/GG vs CC, OR = 1.16, 95%CI = 1.08-1.24, P < 0.001; GG vs CC/CG, OR = 1.24, 95%CI = 1.02-1.49, P = 0.027). In the subgroup analysis, we illustrated the effect of the H63D polymorphism on hepatocellular carcinoma and pancreatic cancer risk, particularly in the Asian and African subgroups; however, this was not observed in gynecological malignant tumors. In summary, this analysis provided strong evidence that the HFE H63D polymorphism may play a critical role in the increased aggressiveness of hepatocellular carcinoma and pancreatic cancer.

Orexin A activates hypoglossal motoneurons and enhances genioglossus muscle activity in rats

BACKGROUND AND PURPOSE

Orexins have been demonstrated to play important roles in many physiological processes. However, it is not known how orexin A affects the activity of the hypoglossal motoneuron (HMN) and genioglossus (GG) muscle.

EXPERIMENTAL APPROACH

GG muscle electromyograms (GG-EMG) were recorded in anaesthetized adult rats after orexin A or orexin receptor antagonists were applied to the hypoglossal nucleus, and in adult rats in which orexin neurons were lesioned with the neurotoxin orexin-saporin (orexin-SAP). HMN membrane potential and firing were recorded from neonatal rat brain slices using whole-cell patch clamp after an infusion of orexin A or orexin receptor antagonists.

KEY RESULTS

Unilateral micro-injection of orexin A (50, 100 or 200 μM) into the hypoglossal nucleus significantly enhanced ipsilateral GG activity in adult rats. Orexin A (4, 20, 100 or 500 nM) depolarized the resting membrane potential and increased the firing rate of HMNs in a dose-dependent manner in the medullary slices of neonatal rats. Both SB 334867, a specific OX1 receptor antagonist and TCS OX2 29, a specific OX2 receptor antagonist not only blocked the depolarized membrane potential and the increased firing rate of HMNs by orexin A in the neonatal model but also attenuated GG-EMG in the adult model. A significant decrease in GG-EMG was observed in adult orexin neuron-lesioned rats compared with sham animals.

CONCLUSION AND IMPLICATIONS

Orexin A activates OX1 and OX2 receptors within the hypoglossal motor pool and promotes GG activity, indicating that orexin A is involved in controlling respiratory motor activity.

Skin immune response in the zebrafish, Danio rerio (Hamilton), to Aeromonas hydrophila infection: a transcriptional profiling approach

Skin plays an important role in innate immune responses to bacterial infection, but its molecular mechanism remains unclear in fish. The transcriptional profiling of the skin immune response to Aeromonas hydrophila infection of the zebrafish, Danio rerio (Hamilton), was performed by Affymetrix microarray analysis. The results showed that 538 genes were differentially expressed, of which 388 genes were up-regulated and 150 genes were down-regulated. The expression patterns for 106 representative genes were observed to be up-regulated in zebrafish skin at 24 and 36 h post-infection, and gene expression changes were clearly greater at 36 h. Gene Ontology classification indicated that 222 genes were significantly associated with the skin immunity, including complement activation, acute-phase response, stress response, chemotaxis and apoptosis. Further Kyoto Encyclopedia of Genes and Genomes analysis showed that the significant pathways included MAPK, p53, Wnt, TGF-β, Notch, ErbB, JAK-STAT, VEGF, mTOR and Calcium signalling in skin immune responses, and several genes (e.g. akt2l, frap1, nras, rac1, xiap) were found to be involved in signalling networks. Moreover, expression changes in nine selected genes were verified by real-time qPCR analysis. This is the first known report on transcriptome analysis in the skin of zebrafish against the pathogen A. hydrophila.

Circadian rhythms of spectral components of heart rate variability

Circadian rhythms of heart rate variability have been widely studied in recent years. However, most previous reports described such rhythms in terms of normalized units of the low- and high-frequency (LF and HF) spectral components. In this study, we analyzed circadian rhythms of spectral components in absolute units and found unexpected results in normal subjects as well as coronary heart disease (CHD) and congestive heart failure (CHF) patient groups. The results indicate that the notion of sympathovagal balance needs to be re-evaluated.

Nanocrystalline alpha-Ni(OH)2 prepared by ultrasonic precipitation

Nanocrystalline alpha-Ni(OH)2 was prepared by an ultrasonic precipitation/stirring method. Results of X-ray diffraction, transmission electron microscopy, infrared, and thermogravimetric measurements confirm that the sample obtained is alpha phase. Compared with the sample prepared without ultrasonic stirring, the crystal structure of the alpha phase sample has been changed from beta phase. The crystalline size of the sample is about 20 nm, which is smaller than the sample produced without ultrasonic stirring (70 nm).

Topoisomerase II poisoning by ICRF-193

Antineoplastic bis(dioxopiperazine)s, such as meso-2,3-bis(2,6-dioxopiperazin-4-yl)butane (ICRF-193), are widely believed to be only catalytic inhibitors of topoisomerase II. However, topoisomerase inhibitors have little or no antineoplastic activity unless they are topoisomerase poisons, a special subclass of topoisomerase-targeting drugs that stabilize topoisomerase-DNA strand passing intermediates and thus cause the topoisomerase to become a cytotoxic DNA-damaging agent. Here we report that ICRF-193 is a very significant topoisomerase II poison. Detection of topoisomerase II poisoning by ICRF-193 required the use of a chaotropic protein denaturant in the topoisomerase poisoning assays. ICRF-193 caused dose-dependent cross-linking of human topoisomerase IIbeta to DNA and stimulated topoisomerase IIbeta-mediated DNA cleavage at specific sites on (32)P-end-labeled DNA. Human topoisomerase IIalpha-mediated DNA cleavage was stimulated to a lesser extent by ICRF-193. In vivo experiments with MCF-7 cells also showed the requirement of a chaotropic protein denaturant in the assays and selectivity for the beta-isozyme of human topoisomerase II. Studies with two topoisomerase IIbeta-negative cell model systems confirmed significant topoisomerase II poisoning by ICRF-193 in the wild type cells and were consistent with beta-isozyme selectivity. Common use of only the detergent, SDS, in assays may have led to failure to detect topoisomerase II poisoning by ICRF-193 in earlier studies.

[Role of angiotensin-(1-7) in amino-acid-neurotransmitter-mediated blood pressure regulation in rat rostral ventrolateral medulla]

The present study was undertaken to investigate the linkage between angiotensin-(1-7) [Ang-(1-7)] and the release of amino acid neurotransmitters in the the rostral ventrolateral medulla (RVLM) by techniques of microinjection, microdialysis combined with high performance liquid chromatography (HPLC)-fluorescent detection. Unilateral microinjection of Ang-(1-7) into the RVLM of anesthetized rats produced an increase in mean arterial pressure (MAP) accompanied by an increased release of glutamate (Glu). In contrast, microinjection of Ang779, a selective antagonist of Ang-(1-7) receptor, caused a decrease in MAP with a decreased release of Glu and an increased release of glycine, taurine and gamma-aminobutyric acid. The pressor effect of Ang-(1-7) and the depressor effect of Ang779 were in part blocked by corresponding antagonists of amino acid receptors. These results suggest that the pressor effect of Ang-(1-7) in the RVLM may be partially due to an increased release of Glu, whereas the depressor effect of Ang779 may be partially attributed to a decreased release of Glu and an increased release of inhibitory amino acid neurotransmitters.

Chloroquinoxaline sulfonamide (NSC 339004) is a topoisomerase IIalpha/beta poison

Chloroquinoxaline sulfonamide (chlorosulfaquinoxaline, CQS, NSC 339004) is active against murine and human solid tumors. On the basis of its structural similarity to the topoisomerase IIbeta-specific drug XK469, CQS was tested and found to be both a topoisomerase-IIalpha and a topoisomerase-IIbeta poison. Topoisomerase II poisoning by CQS is essentially undetectable in assays using the common protein denaturant SDS, but easily detectable with strong chaotropic protein denaturants. The finding that detection of topoisomerase poisoning can be so dependent on the protein denaturant used in the assay has implications for drug discovery efforts and for our understanding of topoisomerase poisons.

The 2-pyridone antibacterial agents: bacterial topoisomerase inhibitors

Many attempts have been made to prepare analogs of 4-quinolone antibacterial agents bearing novel ring systems, which might retain the favorable properties of these widely used antibacterial agents and at the same time increase activity against multidrug-resistant bacteria, streptococci, and anaerobic microorganisms. One such attempt involved bioisosteric exchange of the 1-N atom and 4a-C atom of naphthyridones, quinolones, and benzoxazines to produce a family of highly active pyridopyrimidines, quinolizines, and ofloxacin bioisosteres. These new antibacterial agents have been named collectively as the 2-pyridones. Many hundreds of 2-pyridones have been synthesized and evaluated in vitro and in vivo, and selected members are advancing toward human clinical trials. Preparation of these bioisosteres required the development of enabling chemistry, as previous methods were unsuccessful in producing the needed core structures. This review compares the structure-activity relationships of these agents with known trends among 4-quinolones, from which it is seen that there are many parallels, but also some significant departures as well. Generally, 2-pyridones are more highly active in vitro and in vivo and more water soluble than comparable 4-quinolones. These properties are posited to arise from electronic and conformational alternations in these new substances. Selected members show excellent pharmacodynamic properties, justifying the view that this is a very promising new class of totally synthetic antibacterial agents.

Synthesis and antimicrobial activity of 4H-4-oxoquinolizine derivatives: consequences of structural modification at the C-8 position

The antibacterial 4H-4-oxoquinolizines were introduced recently to overcome bacterial resistance to fluoroquinolones. They exhibit potent antibacterial activity against Gram-positive, Gram-negative, and anaerobic organisms and are highly active against some quinolone-resistant bacteria including quinolone-resistant MRSA. Preliminary studies indicated that oxoquinolizines possess distinct activity and toxicity profiles as compared with their parent quinolones. In order to develop a potent antibacterial agent with the desired spectrum of activity, good tolerability, and balanced pharmacokinetic profile, we synthesized and evaluated a series of oxoquinolizines with various substituents at the C-8 position. Most compounds tested in this study demonstrated better activity against Gram-positive bacteria than ciprofloxacin and exhibited good susceptibility against ciprofloxacin- and methicillin-resistant S. aureus. While maintaining potent in vitro activity, several compounds showed improved in vivo efficacy over ABT-719 as indicated by the mouse protection test. As an example, the oral ED(50) values for the cis-3-amino-4-methylpiperidine analogue 3ss against S. aureus NCTC 10649M, S. pneumoniae ATCC 6303, and E. coli JUHL were 0. 8, 2.0, and 1.4 mg/kg, compared to 3.0, 10.0, and 8.3 mg/kg for ABT-719. The current study revealed that the steric and electronic environment, conformation, and absolute stereochemistry of the C-8 group are very important to the antibacterial profiles. Structural modifications of the C-8 group provide a useful means to improve the antibacterial activities, physicochemical properties, and pharmacokinetic profiles. Manipulation of the C-8 group also allows us to generate analogues with the desired spectrum of activity, such as analogues that are selective against respiratory pathogens.

The 2-pyridone antibacterial agents: 8-position modifications

Improved potency against multiply resistant streptococci and anaerobic microorganisms relative to current antibiotics has been sought by many laboratories around the world. As one result of attempts to prepare analogs of 4-quinolone anti-infectives bearing novel ring systems, the 2-pyridones were discovered. The 2-pyridones, which are bioisosteres of 4-quinolones, are highly active against a wide range of resistant strains of bacteria. Several hundreds of 2-pyridones have been synthesized incorporating modifications at various positions. In order to reduce the complexity of this review, only the widely adopted 8-position modifications (corresponding to the 7-position of the quinolones) will be discussed here. From scientific publications and patents, it is clear that many of the 2-pyridones are very promising candidates and yet only selective members of these compounds have been advanced to detailed preclinical trials. Among the promising candidates, A-170568 was demonstrated to have the best overall profile in terms of the in vitro and in vivo antibacterial activities, safety profile, and tissue penetration.

DNA cleavage activities of Staphylococcus aureus gyrase and topoisomerase IV stimulated by quinolones and 2-pyridones

We have cloned Staphylococcus aureus DNA gyrase and topoisomerase IV and expressed them in Escherichia coli as polyhistidine-tagged proteins to facilitate purification and eliminate contamination by host enzymes. The enzyme preparations had specific activities similar to previously reported values. Potassium glutamate (K-Glu) stimulated the drug-induced DNA cleavage activity and was optimal between 100 and 200 mM for gyrase and peaked at 100 mM for topoisomerase IV. Higher concentrations of K-Glu inhibited the cleavage activities of both enzymes. Using a common buffer system containing 100 mM K-Glu, we tested the enzyme-mediated DNA cleavage activities of both gyrase and topoisomerase IV with oxolinic acid, norfloxacin, ciprofloxacin, trovafloxacin, clinafloxacin, and the 2-pyridone ABT-719. As expected, all drugs tested demonstrated greater potency against topoisomerase IV than against gyrase. In addition, cleavage activity was found to correlate well with antibacterial activity.

Naloxone reverses inhibitory effect of electroacupuncture on sympathetic cardiovascular reflex responses

Acupuncture and electroacupuncture (EA) have been used in traditional Chinese medicine to treat a wide range of diseases and conditions, including angina pectoris and myocardial infarction. In a feline model of reflex-induced reversible myocardial ischemia, electrical stimulation of the median nerves to mimic EA (Neiguan acupoint) significantly improved ischemic dysfunction, secondary to an inhibitory effect of EA on reflex pressor effects evoked by bradykinin (BK). The central mechanism of EA's inhibitory effect in this model is unknown. Accordingly, in alpha-chloralose-anesthetized cats, BK (10 micrograms/ml) was applied to the gallbladder to elicit a cardiovascular reflex response that significantly (P < 0.05) increased arterial blood pressure and heart rate; normalized systolic wall thickening (%WTh) of the left ventricle, measured by ultrasonic single-crystal sonomicrometer, increased by 31 +/- 11% (P < 0.05). After ligation of a side branch of the left anterior descending coronary artery, the reflex pressor response to BK resulted in a significant decrease of %WTh (-32 +/- 6%) in the ischemic region. When bilateral EA of the Neiguan acupoints was performed, the pressor response to BK was inhibited and regional myocardial function was significantly improved (+19 +/- 20%). The inhibitory effects of EA on blood pressure and %WTh were reversed by intravenous injection of naloxone (0.4 mg/kg; n = 9) or microinjection of naloxone (10 nM in 0.1 microliter/site; n = 14) into the rostral ventrolateral medulla (rVLM). Thus %WTh with intravenous naloxone was reduced to -13 +/- 29% (P<0.05) during stimulation of the gallbladder. Our results indicate that the inhibitory effect of EA on the BK-induced pressor response and the consequent improvement of ischemic dysfunction is dependent on the activation of opioid receptors, specifically receptors located in the rVLM.

[Inhibitory effect of electroacupuncture on the cardiovascular response evoked by applying bradykinin on the gallbladder]

The effects of electroacupuncture (EA) on the pressor response and reversible myocardial dysfunction induced by application of bradykinin (BK) on the gallbladder were studied in cats anesthetized with alpha-chloralose. The cardiovascular responses evoked by application of BK included a pressor response, an increase of LVP and its dP/dtmax, tachycardia and a decrease of local wall motion of the left ventricle with a supplying branch of the left anterior descending coronary artery ligated beforehand. Following EA of bilateral Neiguan acupionts, the pressor response of BK was inhibited, while the regional left ventricle myocardial dysfunction was alleviated significantly. The effects of EA were reversed by i.v. injection of naloxone (0.4 mg/kg). Our results indicate that EA has an inhibitory effect on the BK-induced pressor and ischemic dysfunction, which may be related with endogenous opioid peptide.

[The coherence analysis between neuronal discharge in the rostral ventrolateral medulla and the cardiovascular activity in rats]

To analyze the coherence between neuronal discharges (ND) in the rostral ventrolateral medulla (RVLM) and the cardiovascular activity, we observed the neuronal discharge in RVLM responding to electric stimulation of the defense area of the mid-brain. Fast Fourier transform (FFT) was performed to analyze the coherence between the signals of ND and blood pressure to determine if the ND were cardiac rhythmic. The coherence between ND variability (NDV) and heart rate variability (HRV) was also analyzed. The results showed: (1) majority of the neurons (67%) were excited responding to electric stimulation in the defense area of the mid-brain; (2) the electric activity of about 70% of the neurons were substantially inhibited by administration of phenylephrine; (3) 64% of the neurons were actively synchronous with cardiac cycle; and (4) significant coherence between NDV and HRV in HF component was shown in a half of the neurons (50%). The coherence analysis thus provides a new tool to investigate the regulation of the autonomic nervous system.

Synthesis and structure-activity relationships of 2-pyridones: II. 8-(Fluoro-substituted pyrrolidinyl)-2-pyridones as antibacterial agents

The 8-position side chain of 2-pyridones is believed to be involved in the binding with bacterial DNA gyrase to form the ternary complex, making them very important for the activity of 2-pyridones. A series of 2-pyridones having fluoro-substituted amines at the 8-position has been synthesized and their antibacterial activities and parmacokinetic properties are reported.

[The central mechanism of the high frequency component in heart rate variability in rat]

Experiments were performed on 15 Sprague-Dawley rats to detect the effect of artificial ventilation of different frequencies on the high frequency component of heart rate variability (HRV) by autoregressive modeling with Burg algorithm. With continuous or intermittent electrical stimulation, different patterns of regulating activity of nucleus ambiguus in medulla on HRV were observed. Fast Fourier transform was used to analyze the coherence between neuronal discharge with respiratory rhythm in rostral ventrolateral medulla (rVLM) and HRV. The results showed that (1) the central frequency of high frequency (HF) component of HRV were moved closely with frequencies of artificial ventilation, (r = 0.83, P < 0.0001); (2) there was a favorable coherence between neuronal discharge with respiratory rhythm in rVLM and HRV in HF on spectrum, (k2 = 0.854 +/- 0.1); (3) the area of HF component in HRV was increased significantly during intermittent electrical stimulation of nucleus ambiguus in medulla. The central frequency of HF component in HRV was influenced mainly by frequencies of respiration. These results indicate a significant correlation between the HF in HRV and neuronal discharge with respiratory rhythm in rVLM, suggesting that rVLM participates in the regulation of HRV. The HF component of HRV may reflect mainly the fluctuating activity of vagal center. Coherence analysis of two signals provides a new method to confirm the type and interaction of neurons in the central cardiovascular system.

A simple, inexpensive apparatus for performance of preparative scale solution phase multiple parallel synthesis of drug analogs. II. Biological evaluation of a retrospective library of quinolone antiinfective agents

A series of pure fluoroquinolone antiinfective agents was prepared by multiple parallel synthesis using a simple new apparatus. These compounds were evaluated biologically against Gram-positive and Gram-negative microorganisms and against a BCG strain transfected with luciferase in a fluorescence-based antitubercular assay. Activity against relatively fast growing, acid-fast Mycobacterium smegmatis was determined in part by agar-dilution streak assays. Data obtained against Escherichia coli-derived DNA gyrase does not correlate well with whole cell assays against E. coli. These compounds were assayed by a convenient glass-fiber filter binding method modified for high throughput screening. In these analogs, the results with a N-1 cyclopropyl substituent were often inferior to those obtained with a N-1 2',4'-difluorophenyl substituent. None of the new compounds prepared was superior in its antimycobacterial potency to ciprofloxacin or temafloxacin.

Cloning and functional studies of splice variants of the alpha-subunit of the amiloride-sensitive Na+ channel

The alpha-subunit of the amiloride-sensitive epithelial Na+ channel (alpha ENaC) is critical in forming an ion conductive pore in the membrane. We have identified the wild-type and three splice variants of the human alpha ENaC (h alpha ENaC) from the human lung cell line H441, using RT-PCR. These splice variants contain various structures in the extracellular domain, resulting in premature truncation (h alpha ENaCx), 19-amino acid deletion (h alpha ENaC-19), and 22-amino acid insertion (h alpha ENaC + 22). Wild-type h alpha ENaC and splice variants were functionally characterized in Xenopus oocytes by coexpression with hENaC beta- and gamma-subunits. Unlike wild-type h alpha ENaC, undetectable or substantially reduced amiloride-sensitive currents were observed in oocytes expressing these splice variants. Wild-type h alpha ENaC was the most abundantly expressed h alpha ENaC mRNA species in all tissues in which its expression was detected. These findings indicate that the extracellular domain is important to generate structural and functional diversity of h alpha ENaC and that alternative splicing may play a role in regulating hENaC activity.

Synthesis and structure-activity relationships of 2-pyridones: a novel series of potent DNA gyrase inhibitors as antibacterial agents

Two novel series of 2-pyridones were synthesized by transposition of the nitrogen of 4-quinolones to the bridgehead position. This subtle interchange of the nitrogen atom with a carbon atom yielded two novel heterocyclic nuclei, pyrido[1,2-alpha]pyrimidine and quinolizine, which had not previously been evaluated as antibacterial agents and were found to be potent inhibitors of DNA gyrase. Quinolizines with a methyl group at the 9-position such as (S)-45a (ABT-719) demonstrate exceptional broad spectrum antibacterial activity. Most notably, they are active against resistant bacteria such as methicillin-resistant Staphylococcus aureus, vancomycin-resistant strains of enterococci, and ciprofloxacin-resistant organisms. In addition, 2-pyridones also possess favorable physiochemical and pharmacokinetic properties. These 2-pyridones were synthesized from the commercially available starting materials by 10-17 linear transformations. The structure of an adduct yielded by this sequence, (S)-45a (ABT-719), was determined by X-ray crystallographic analysis.

Mechanism of differential activities of ofloxacin enantiomers

Ofloxacin, a potent quinolone antibacterial agent, has a tricyclic ring structure with a methyl group attached to the asymmetric carbon at the C-3 position on the oxazine ring. The S isomer (DR-3355) of ofloxacin has antibacterial activity up to 2 orders of magnitude greater than that of the R isomer (DR-3354). This differential antibacterial activity was not due to different drug transport mechanisms of the two isomers but was found to be derived from the inhibitory activity against the target enzyme, DNA gyrase. Previous mechanistic studies have suggested that the bactericidal effect of the drug is mediated through the stabilization of a cleavable complex via a cooperative drug binding process to a partially denatured DNA pocket created by DNA gyrase. The drug binds to supercoiled DNA in a manner similar to that to which it binds to the enzyme-DNA complex. In the present studies, we first examined the binding of the two radiolabeled ofloxacin enantiomers to supercoiled pUC9 plasmid DNA. Surprisingly, the two enantiomers possessed similar apparent binding affinities and binding cooperatives. The major difference in binding between the two stereoisomers was the molar binding ratio: 4 for the more active S isomer versus 2 for the less active R isomer. We next examined the relative binding potencies of the stereoisomers to the DNA-DNA gyrase complex. The results of a competition assay showed that (S)-ofloxacin binds 12-fold better to the complex than (R)-ofloxacin. The binding potencies of the two enantiomers and two other quinolones correlated well with their respective concentrations causing 50% inhibition against DNA gyrase. The results are interpreted by a stacking model by using the concept of the cooperative drug-DNA binding mechanism, indicating that the potencies of quinolones cannot be determined solely by the DNA binding affinity and cooperativity but can also be determined by their capability in maximally saturating the binding site. The capability of the drug in saturating the binding pocket manifests itself in an increased efficacy at inhibiting the enzyme through a direct interaction between the drug and the enzyme. The results augment the previous suggestion that the binding pocket in the enzyme-DNA complex involves multiple receptor groups including not only DNA bases but also a gyrase subunit. The higher level of potency of (S)-ofloxacin is proposed to derive from the fact that a greater number of molecules are assembled in the pocket. This greater number of molecules optimizes the interaction between the drug and the enzyme, possibly through a contact between the C-7 substituent and the quinolone pocket on the B subunit of DNA gyrase.

Quinobenoxazines: a class of novel antitumor quinolones and potent mammalian DNA topoisomerase II catalytic inhibitors

The antineoplastic quinobenoxazines A-62176 and A-74932 were shown to be potent inhibitors of mammalian DNA topoisomerase II in vivo. This was demonstrated by their selective inhibition of the SV40 DNA replication stages that require topoisomerase II. Neither drug stabilized a covalent complex of the enzyme with SV40 DNA, which suggests that they are not poisons of DNA topoisomerase II. A-77601, an analog having little antitumor activity, barely inhibited DNA topoisomerase II in vivo, even at high concentrations. These findings were supported by in vitro studies which showed that A-62176 and A-74932, but not A-77601, strongly inhibited the catalytic activity of mammalian DNA topoisomerase II. A-62176 did not cause topoisomerase II-mediated DNA strand breaks in vitro under conditions in which adriamycin produced extensive DNA breakage. The antineoplastic and topoisomerase inhibitory activities of the quinobenoxazines correlate with their ability to unwind DNA. A-62176 antagonized the poisoning of topoisomerase II by VM-26 in vivo and in vitro, but had no effect on DNA breakage induced by camptothecin, a DNA topoisomerase I poison. A-62176 and A-74932 thus inhibit DNA topoisomerase II reactions at a step prior to the formation of the "cleavable complex" intermediate. These findings indicate that stabilization of the DNA topoisomerase II-DNA cleavable complex is not necessary for the antitumor activity of this class of quinolones and that the catalytic inhibition of DNA topoisomerase II may contribute significantly to the anticancer activity of other DNA topoisomerase II inhibitors.

DNA topoisomerases from pathogenic fungi: targets for the discovery of antifungal drugs

DNA topoisomerases, a class of enzymes that change the topological structure of DNA, have been shown to be the target of many therapeutic agents, including antibacterial agents (quinolones) and anticancer agents. These drugs inhibit the enzyme in a unique way so that the enzyme is converted into a cellular poison. Candida albicans and Aspergillus niger are two major opportunistic fungal pathogens. Our results show that these fungi have high levels of both type I and type II topoisomerases (with a minimum of 5 x 10(5) ATP-independent relaxation units and 2 x 10(5) P-4 unknotting units per liter of wild-type C. albicans). The ATP-dependent type II topoisomerase (termed C. albicans topoisomerase II) was purified by approximately 2,000-fold from C. albicans cells by using a simple isolation scheme that consists of three column procedures: hydroxylapatite, phosphocellulose, and heparin-agarose chromatographies. The responses of the Candida and the calf thymus topoisomerase II to some known topoisomerase II inhibitors were measured. Etoposide and 4'-(9-acridinylamino)methanesulfon-m-anisidide, compounds known to inhibit catalysis and to enhance DNA breakage by mammalian topoisomerase II, and A-80198, an etoposide derivative, enhanced cleavage by both enzymes at similar concentrations of these compounds, with the response of the calf thymus topoisomerase II from slightly to fourfold higher in magnitude than the response of the Candida enzyme in the same concentration range. In contrast, A-75272 (a cytotoxic tricyclic quinolone) shows a slightly stronger DNA cleavage enhancement effect with the Candida enzyme than with the mammalian counterpart. The abundance of the enzyme in cells and the different drug responses of the host enzyme and the fungal enzyme suggest that the fungal topoisomerase may serve as a target for the discovery of effective and safe antifungal agents.

Characterization of DNA topoisomerase I from Candida albicans as a target for drug discovery

Candida albicans is an opportunistic pathogen responsible for life-threatening infections in persons with impaired immune systems. Topoisomerase I is a potential target for novel antifungal agents; however, in order for this enzyme to be a therapeutically useful target, it needs to be demonstrated that the fungal and human topoisomerases differ sufficiently as to allow the fungal topoisomerase to be selectively targeted. To address this question, we isolated the topoisomerase I from C. albicans and compared its biochemical properties with those of the mammalian enzyme. Similar to other eukaryotic type I topoisomerases, the C. albicans type I topoisomerase has an apparent molecular mass of 102 kDa and covalently links to the 3' end of DNA, as shown after the reaction is interrupted by sodium dodecyl sulfate. Topoisomerase poisons such as camptothecin act by stabilizing the cleavage complex formed by the topoisomerase I and DNA. We observed that the C. albicans and mammalian type I topoisomerases differ in that the C. albicans cleavage complex is approximately 10-fold less sensitive to camptothecin than the mammalian cleavage complex is. In addition, we found that the antifungal agent eupolauridine can stabilize the cleavage complex formed by both the C. albicans and human topoisomerases and that the response of the C. albicans topoisomerase I to this drug is greater than that of the human enzyme. Thus, the topoisomerase I from C. albicans is sufficiently distinct from the human enzyme as to allow differential chemical targeting and will therefore make a good target for antifungal drug discovery.

Antitumor activity and biochemical effects of topsentin

Topsentin, a bis(indolyl)imidazole marine natural product, inhibited the proliferation of cultured human and murine tumor cells at micromolar concentrations (IC50 values ranged from 4 to 40 microM) and was active against in vivo P388 leukemia (%T/C = 137, 150 mg/kg, QD1-5) and B16 melanoma (%T/C = 144, 37.5 mg/kg, QD1-9) tumors. Effects of 30 microM topsentin (1-hr exposures) on incorporation of radiolabeled precursors by P388 cells indicated inhibition of DNA synthesis (91%) and to a lesser extent RNA synthesis (57%), whereas synthesis of protein was unaffected (0%). Fluorescence spectral changes and competitive binding experiments with ethidium bromide indicated that topsentin interacted with DNA. No evidence for intercalation was observed in DNA unwinding studies, but competitive binding experiments with Hoechst 33342 and CC-1065 indicated that topsentin bound to DNA in the minor groove.

[Effect on electroacupuncture on experimental epilepsy--power spectrum analysis of EEG]

The present study was undertaken to investigate the effect of electroacupuncture (EA) on electroconvulsive shock (ECS) and penicillin-induced convulsions in rats, using power spectrum analysis technique. Under quiet state, delta and theta bands were found to be predominant in the power spectrum of spontaneous EEG's with the peak of the main power in the delta band. During ECS and penicillin-induced convulsions, the power percentage of the delta band decreased, while those of alpha and beta bands increased. The bands with the peak of the main power shifted to the right, and the total power was distinctly enhanced. No marked change in background EEG activity was observed during EA stimulation. In the case of EA plus ECS or penicillin-induced convulsions, the power percentage of the delta band increased, while those of alpha and beta bands decreased. The peak of the main power returned to the delta band with a decreased total power. The compressed power spectrum array showed distinct suppression of convulsions by EA audio-visually. These results suggest that EA enables the EEG to synchronize and enhances the inhibitory process of the brain, thereby plays its anticonvulsant role.

Mechanism of inhibition of DNA gyrase by quinolone antibacterials: a cooperative drug--DNA binding model

We have proposed a cooperative quinolone-DNA binding model for the inhibition of DNA gyrase. The essential feature of the model is that bound gyrase induces a specific quinolone binding site in the relaxed DNA substrate in the presence of ATP. The binding affinity and specificity are derived from two unique and equally important functional features: the specific conformation of the proposed single-stranded DNA pocket induced by the enzyme and the unique self-association phenomenon (from which the cooperativity is derived) of the drug molecules to fit the binding pocket with a high degree of flexibility. Supporting evidence for and implications of this model are provided.

Mechanism of inhibition of DNA gyrase by quinolone antibacterials: specificity and cooperativity of drug binding to DNA

Although the functional target of quinolone antibacterials such as nalidixic acid and norfloxacin has been identified as the enzyme DNA gyrase, the direct binding site of the drug is the DNA molecule [Shen, L. L., & Pernet, A. G. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 307-311]. As described in this paper, binding specificity and cooperativity of quinolones to DNA were further investigated with the use of a variety of DNA species of different structures and different base compositions. Results show that the drug binding specificity is controlled and determined largely by the DNA structure. The drug binds weakly and demonstrates no base preference when DNA strands are paired. The drug binds with much greater affinity when the strands are separated, and consequently, binding preference emerges: it binds better to poly(G) and poly(dG) over their counterparts including poly(dI). The results suggest that the drug binds to unpaired bases via hydrogen bonding and not via ring stacking with DNA bases. The weak binding to relaxed double-stranded DNA and the stronger binding to single-stranded DNA are both nonspecific as they do not demonstrate binding saturation and cooperativity. The specific type of binding, initially demonstrated in our previous publication with the supercoiled DNA and more recently with complex formed between linear DNA and DNA gyrase [Shen, L. L., Kohlbrenner, W. E., Weigl, D., & Baranowski, J. (1989) J. Biol. Chem. (in press)], occurs near the drug's supercoiling inhibition concentration. As shown in this paper, binding saturation curves of this type are highly cooperative (with Hill constant greater than 4).(ABSTRACT TRUNCATED AT 250 WORDS)

Mechanism of quinolone inhibition of DNA gyrase. Appearance of unique norfloxacin binding sites in enzyme-DNA complexes

As a means of gaining additional information on the topoisomerase-mediated cytotoxicity induced by a variety of antibacterial and antitumor compounds we have examined the interaction of the quinolone anti-bacterial agent, norfloxacin, with the bacterial topoisomerase, DNA gyrase. Membrane filtration and spin-column techniques were used to study the binding of [3H]norfloxacin to purified plasmid DNA, DNA gyrase, and complexes formed by adding gyrase to different forms of plasmid DNA. Consistent with previous results (Shen, L. L., and Pernet, A. G. (1985) Proc. Natl. Acad. Sci. U.S.A. 82, 301-311) little [3H]norfloxacin binds to reconstituted gyrase, but significant levels of drug bind nonspecifically to relaxed DNA. However, when DNA and gyrase are incubated together additional norfloxacin binding sites are detectable. These complex-dependent sites are distinguishable from those sites involved in nonspecific DNA binding in that the complex-dependent sites are saturable and they retain bound norfloxacin after centrifuging the complex through a spin column. In addition, extent of binding is influenced by the topological state of DNA used to form the complex. The complex-dependent norfloxacin binding sites are likely involved in the inhibition of the enzyme since saturation of these sites occurs in the same norfloxacin concentration range as the inhibition of DNA supercoiling activity. Moreover, there is a close correlation of norfloxacin-induced DNA breakage with levels of norfloxacin bound to complexes of gyrase and relaxed DNA. These findings provide the first direct correlation of quinolone binding with inhibition of enzyme activity and induction of DNA breakage, and they suggest that the inhibition of DNA gyrase by norfloxacin occurs as a result of binding to a site which appears after the formation of a gyrase-DNA complex.

Chiral DNA gyrase inhibitors. 2. Asymmetric synthesis and biological activity of the enantiomers of 9-fluoro-3-methyl-10-(4-methyl-1-piperazinyl)-7-oxo-2,3-dihydro-7H- pyrido[1,2,3-de]-1,4-benzoxazine-6-carboxylic acid (ofloxacin)

A short and efficient synthesis, starting with (R)- and (S)-alaninol, of the two optical antipodes of the quinolone antimicrobial agent ofloxacin has been devised. Testing in vitro of the products against a range of bacteria and in an assay system incorporating purified DNA gyrase from different bacterial species demonstrates that the S-(-) enantiomer is substantially the more active.

Chiral DNA gyrase inhibitors. 1. Synthesis and antimicrobial activity of the enantiomers of 6-fluoro-7-(1-piperazinyl)-1-(2'-trans-phenyl-1'-cyclopropyl)-1, 4-dihydro-4-oxoquinoline-3-carboxylic acid

New quinolone antimicrobial agents (racemic, (1'S,2'R)- and (1'R,2'S)-6-fluoro-7-(1-piperazinyl)-1-(2'-trans-phenyl-1'-cyclopropyl)- 1, 4-dihydro-4-oxoquinoline-3-carboxylic acids) were synthesized, and their in vitro antimicrobial potencies and spectra were determined. As compared to their conceptual parents, these agents retained a considerable amount of the antimicrobial potency and spectra of ciprofloxacin and of 6-fluoro-1-phenyl-7-(1-piperazinyl)-1,4-dihydro-4-oxoquinoline-3-carboxy lic acid against Gram-positives. Gram-negatives were considerably less sensitive. The (-)-(1'S,2'R) analogue was the more potent of the enantiomers, but the degree of chiral discrimination by most bacteria was only 4-fold. The 4-fold chiral discrimination was observed also using purified DNA gyrase obtained from Micrococcus luteus, whereas the two enantiomers were essentially equiactive against the enzyme derived from Escherichia coli. These results confirm that there is a substantial degree of bulk tolerance available at N-1 of quinolone antimicrobial agents and suggest that electronic factors controlled by substitution at that site are of considerable importance. On the other hand, chiral recognition brought about by attachment of optically active groups to the N-1 position in these derivatives is relatively small.

Valve prolapse in Behçet's disease

Valve prolapse was diagnosed solely by echocardiography in three consecutive patients with Behçet's disease. Two patients had prolapse of the posterior mitral valve leaflet, but no clinical manifestations of valve prolapse. In the third patient aortic valve prolapse was associated with physical signs of aortic regurgitation and left ventricular failure. Valve prolapse in these cases may have resulted from structural and functional derangement caused by the underlying non-specific vasculitis that occurs in Behçet's disease.