[Study of the urban-impact on microbial communities and their virulence factors and antibiotic resistance genomes in the Nandu River, Haikou]

Objective: To explore the changes in bacterial community structure, antibiotic resistance genome, and pathogen virulence genome in river water before and after the river flowing through Haikou City and their transmission and dispersal patterns and to reveal anthropogenic disturbance's effects on microorganisms and resistance genes in the aquatic environment. Methods: The Nandu River was divided into three study areas: the front, middle and rear sections from the upstream before it flowed through Haikou City to the estuary. Three sampling sites were selected in each area, and six copies of the sample were collected in parallel at each site and mixed for 3 L per sample. Microbial community structure, antibiotic resistance, virulence factors, and mobile genetic elements were analyzed through bioinformatic data obtained by metagenomic sequencing and full-length sequencing of 16S rRNA genes. Variations in the distribution of bacterial communities between samples and correlation of transmission patterns were analyzed by principal co-ordinates analysis, procrustes analysis, and Mantel test. Results: As the river flowed through Haikou City, microbes' alpha diversity gradually decreased. Among them, Proteobacteria dominates in the bacterial community in the front, middle, and rear sections, and the relative abundance of Proteobacteria in the middle and rear sections was higher than that in the front segment. The diversity and abundance of antibiotic resistance genes, virulence factors, and mobile genetic elements were all at low levels in the front section and all increased significantly after flow through Haikou City. At the same time, horizontal transmission mediated by mobile genetic elements played a more significant role in the spread of antibiotic-resistance genes and virulence factors. Conclusions: Urbanization significantly impacts river bacteria and the resistance genes, virulence factors, and mobile genetic elements they carry. The Nandu River in Haikou flows through the city, receiving antibiotic-resistant and pathogen-associated bacteria excreted by the population. In contrast, antibiotic-resistant genes and virulence factors are enriched in bacteria, which indicates a threat to environmental health and public health. Comparison of river microbiomes and antibiotic resistance genomes before and after flow through cities is a valuable early warning indicator for monitoring the spread of antibiotic resistance.

[Epidemiological characteristics of typhus in China, 1950-2021]

Objective: To analyze the epidemiological characteristics of typhus in China from 1950 to 2021, and discuss the challenges in typhus prevention and control in China and suggest future prevention and control strategies. Methods: Based on the reported data of typhus from 1950 to 2021 in China from the Infectious Disease History Database of China Public Health Science Data Center and the National Notifiable Infectious Disease Reporting Information System of Chinese Center for Disease Control and Prevention, we conducted a descriptive statistical analysis. Mann-Kendall test and circular distribution method were used to analyze the incidence, mortality and case fatality of typhus to reveal the temporal, spatial and population distributions and diagnosis of typhus in China. Results: From 1950 to 2021, a total of 452 965 typhus cases and 7 339 typhus deaths were reported in China, with the cases numbers exceeding 10 000 in 14 years of the 1950s, 1960s and 1980s, respectively. Since 1990s, the reported cases and incidence rate of typhus have decreased dramatically and the most cases were sporadic. However, the reported typhus cases in Anhui, Hubei, Hunan Provinces showed significant uptrends. Although typhus could occur all the year round, but the seasonality was observed with the incidence mainly in summer and autumn. For different provinces from the north to the south, the peaks of typhus' monthly incidence tended to shift to earlier dates. The male to female ratio of the cases was 1.01∶1 (18 529∶18 366). However, more cases occurred in women in recent years. The cases aged ≤9 years accounted for the highest proportion (18.9%), but the number of cases aged ≥50 years showed an upward trend. Most cases were farmers with the proportion increasing year by year. Moreover, the cases in students and scattered-living children also accounted for relatively higher proportions. The median of the interval between onset and diagnosis of typhus was 6 days. Most cases were clinically diagnosed, while the proportion of laboratory-confirmed cases was low and most laboratory cases were confirmed by Well-Felix reaction. Conclusions: Although the incidence and mortality of typhus in China has decreased significantly, the risk for local typhus outbreaks still exists. The prevention and control of typhus still face many challenges. It is indispensable to strengthen the pathogen detection and surveillance for typhus in China.

[Establishment and evaluation of a method for phages enrichment by ferric trichloride-polyvinylidene fluoride membrane filter]

Objective: To establish and evaluate a method of enriching bacteriophages in natural water based on ferric trichloride-polyvinylidene fluoride (FeCl₃-PVDF)membrane filter. Methods: Based on the principle of flocculation concentration, the method of recovering bacteriophage from water sample was established by using iron ion flocculation combined with membrane filter. The titer of phage was determined by Agar double layer method. The recovery efficiency of phage was detected by phage fluorescence staining and real-time fluorescence PCR reaction. Water samples from different sources were collected for simulation experiment to evaluate the enrichment effect. At the same time, the sewage discharged from hospitals was taken as the actual water sample, and the common clinical drug-resistant bacteria were used as the host indicator bacteria to further analyze the enrichment effect of FeCl₃-PVDF membrane filter rapid enrichment method on the bacteriophage in natural water samples. Results: The method of enrichment of bacteriophages in natural water by iron ion concentration 50 mg/L and PVDF membrane filter was established. The recovery rate of this method for bacteriophage was 93%-100%. Under the multi-functional microscope, it was found that the bacteriophage of the enriched water sample increased significantly and the fluorescence value of the enriched water sample determined by the enzyme labeling instrument was about 13 times as high as that before enrichment. After concentration of the actual water samples from the hospital drainage, the positive rate of bacteriophage isolation in the concentrated group and the non-concentrated group was 23% and 4%, and the fluorescence value in the concentrated group was 2-24 times as high as that of the non-concentrated group. Conclusion: The method of FeCl₃-PVDF membrane filter is a simple, efficient and rapid method for enriching bacteriophages in different water samples.

[Drug resistance and genomic characteristics of a strain of O139 Vibrio cholerae isolated from human bloodstream infection]

Objective: To analyze the drug resistance and genomic characteristics of a strain of serogroup O139 Vibrio cholerae producing cholera toxin isolated from the bloodstream of a person with bacteremia. Methods: The broth dilution method and automatic drug sensitivity analyzer were used to determine the antibiotic sensitivity of the strain. The complete genome sequence of the strain was obtained by using second-generation gene sequencing and nanopore sequencing. BLAST software was used for comparison and analysis with CARD, Resfinder, ISfinder, VFDB, and other databases. The drug-resistant genes, insertion sequences and virulence genes carried by the strain were identified. MEGA 5.1 software was used to construct a genetic phylogenetic tree based on the core genomic single nucleotide polymorphisms. Results: V. cholerae SH400, as the toxigenic strain, carried multiple virulence-related genes and four virulence islands. The strain was resistant to streptomycin, tetracycline and cotrimoxazole, carrying corresponding drug-resistant genes. The strain also carried IncA/C plasmid with the size of 172914 bp and contained 10 drug-resistant genes. Combined with the genomic evolutionary relationship, this study found that the drug-resistant genes and drug-resistant plasmids carried among strains showed certain aggregation. The traditional ST type of strain SH400 was ST69, and the cgMLST type was a new type highly similar to cgST-252. Conclusion: This strain of serogroup O139 V. cholerae carries the ctxAB gene, multiple drug-resistant genes and IncA/C plasmid, and there are multiple drug-resistant islands.

[Establishment of multi-sector collaborative mechanism and surveillance network for Salmonella infection outbreak response and control]

Salmonellosis is one of the common food-borne diseases, local and cross-region outbreaks are not rare. The risk of cross-border transmission of Salmonella is increasing with the high frequency of global economic trades. The recently occurred multi-country outbreaks of Salmonella Typhimurium infection associated with chocolate products have highlighted the importance of improving capability of surveillance and warning of foodborne-disease, especially salmonellosis, in China. It is essential to strengthen the collaboration among clinical medicine, disease control and food safety institutions, improve the capability of whole-genome sequencing of Salmonella for the disease surveillance and tracing, and facilitate the information sharing and collaboration among the food safety related sectors for the timely detection, prevention and control of outbreaks of Salmonella infection in China.

[Application and reflection of laboratory-based monitoring in early warning of infectious diseases]

Despite the fact that our cognition towards infectious disease prevention, the advanced technology and the economic status of the whole society has made a great progress in the last decade, the outbreak of COVID-19 pneumonia has again enabled the public to acquire more about super-challenges of infectious diseases, epidemics and the relevant preventive measurements. In order to identify the epidemic signals in early stage or even before the onset of epidemic, the data research and utilization of a series of factors related to the occurrence and transmission of infectious diseases have played a significant role in research of prevention and control during the whole period of surveillance and early warning. Laboratory-based monitoring for the etiology has always been an important part of infectious disease warning system due to pathogens as the direct cause of such diseases. China has initially established a laboratory-based monitoring and early warning system for bacterial infectious diseases based on the Chinese Pathogen Identification Network with an aim to identify pathogens, outbreaks and sources. This network has played an essential role in early detection, tracking and precise prevention and control of bacterial infectious diseases, such as plague, cholera, and epidemic cerebrospinal meningitis. This issue focuses on the function of laboratory-based monitoring during the period of early warning, prevention, and control of bacterial infectious diseases, and conducted a wide range of researches based on the analysis of the epidemic and outbreak isolates, together with field epidemiological studies and normal monitoring systems. All of these could illustrate the effect of laboratory surveillance in the infectious disease risk assessment and epidemic investigation. At the same time, we have put forward our review and expectation of scenarios about laboratory-based monitoring and early warning technologies to provide innovative thoughts for promoting a leapfrog development of infectious disease monitoring and early warning system in China.

[Advance on research and application of laboratory pathogen monitoring and early warning technology of bacterial infectious diseases]

Human beings are still facing the public health challenges from bacterial infectious diseases. Carrying out systematic infectious disease monitoring and early warning is the most direct solution to prevent and control infectious diseases. Etiology is an important part of infectious disease monitoring and early warning. Effective pathogen monitoring can identify pathogens, outbreaks and sources at the first time. In this study, we have reviewed the research and application of etiology monitoring and early warning technology of bacterial infectious diseases and summarized the importance and application scenarios of etiology in infectious disease monitoring and early warning, as well as the research progress of etiology monitoring and early warning technology. Based on the work of existing laboratory monitoring networks, such as Chinese Pathogen Identification Network, the development trend and prospect of infectious disease laboratory network monitoring are put forward to provide a reference for establishing and perfecting the infectious disease monitoring and early warning system.

[Research progress on bacterial resistance and gene carrying resistance in migratory birds]

Bacterial resistance is a serious problem in use of antibiotics and an urgent global public health challenge. The drug-resistant bacteria and drug-resistant genes carried by migratory birds are not only related to clinical antibiotics, but also the use of pesticides and veterinary drugs as well as the pollution of the surrounding environment of drug factories. However, studies on drug-resistant genes carried in migratory birds have been gradually reported around the world. Migratory birds have the characteristics of large range of movement and long flight distance, which leads to the complexity of bacterial resistance. Under the influence of environment and human activities, drug-resistant genes carried in bacteria are transmitted among species,human beings, domestic animals, environment and wild birds through mobile elements. This study summarizes the current situation of antibiotic resistance bacteria carried by migratory birds,the status of drug-resistant genes in migratory birds and the relationship between the resistance of migratory birds and the environment and human activities. The aim is to better understand the important role of migratory birds as hosts and vectors in the global spread of antibiotic resistance.

[Current status, progress and suggestions regarding prevention and control of brucellosis in China]

Brucellosis is a neglected zoonosis, which not only endangers health of the people but also affects the development of animal husbandry, tourism and international trade as well as food safety. In the past two decades, great progress has been achieved in the prevention and control of both human and animal brucellosis, however, tremendous challenges still exists in the control and eradication of brucellosis, especially in the developing countries. In recent years, along with the increase of livestock breeding and animal or related product trade, human contacts with livestock has increased, resulting in the expansion of brucellosis endemic areas. In China, the brucellosis endemic areas are mainly distributed in Inner Mongolia and adjacent provinces, which might be explained by a lot of reasons, such as the development of animal husbandry, emerging and re-emerging of brucellosis endemic area and the movement of infection sources and degree of paid-attention. This paper summarizes the current status and progress in brucellosis prevention/control and surveillance in China and puts forward suggestions for the future improvement.

[Genomic recombination of the vibrio cholerae serogroup O1 El Tor pandemic strains]

Objective: To analyze the genomic recombination of the vibrio cholerae serogroup O1 El Tor pandemic strains. Methods: A total of 292 complete or draft genome sequences of Vibrio cholerae O1 serogroup El Tor strains isolated from 1937 to 2015 were selected from National Biotechnology Information Center database. The genome alignment of strains was computed by snippy software by using N16961 as reference sequence. Then ClonalFrameML software was used to do the recombinant analysis. The wilcox.test function in agricolae package was used to compare the number recombinant segments and the total length of recombinant regions between small and large chromosomes. The kruskal function was used to compare the number recombinant segments and the total length of recombinant regions among different isolation continents. The KOBAS tool was used to do the gene ontology enrichment analysis of recombinant hotspot genes. Results: Of all 292 strains of Vibrio cholerae, 163 strains (55.8%) were recombined. The median of normalized recombinant segment number of small chromosome was 4.7×10(-6) (9.3×10(-7), 2.0×10(-5)), which was significantly larger than that of large chromosome [2.4×10(-6) (3.4×10(-7), 5.7×10(-6))] (P<0.001). The median (P(25),P(75)) of recombinant segment number of strains isolated from Africa, Asia, Europe, North America and South America were 23(1.0,33.0), 1.0(0.0,34.0), 6.0(2.0,13.0), 0.0(0.0,1.0) and 29.5(6.8,56.8), respectively, and the difference was statistically significant (P<0.001). The median (P(25),P(75)) of total length of recombinant regions of strains isolated from Africa, Asia, Europe, North America and South America were 233.0(4.0, 461.0), 11.0(0.0, 695.5), 56.0(4.0,111.0), 0.0(0.0,9.0) and 347.5(132.8,1 323.5) bp, respectively, and the difference was statistically significant (P<0.001). Gene ontology Enrichment analysis showed that the functions of 62 recombinant hotspot genes were mainly enrichment in chemotaxis, taxis, response to external stimulus, receptor activity and molecular transducer activity. Conclustion: In this study, we found that there were significant differences in the number of recombinant fragments and the length of recombinant regions between large and small chromosomes of Vibrio cholerae El Tor. We also found significant differences in the number of recombinant fragments and the total length of recombinant regions among different continents.

[Study on the mechanism of serotype conversion of historical isolates of Shigella flexneri]

Objective: The serotype screening of Shigella flexneri from 1934 to 1965 preserved by the National Center for Medical Culture Collections was carried out, and the molecular characteristics of the serotype conversion strains were studied. Methods: Serotyping of Shigella flexneri in this study was conducted by slide agglutination and multiplex PCR, respectively. The gtrⅡ gene sequence alignment and pulsed field gel electrophoresis typing were performed on the serotype conversion strains. Results: Among the 255 strains of Shigella flexneri preserved in CMCC (B) from 1934 to 1965, 79 were carrying gtrⅡ gene, of which 19 strains and 1 strain were agglutinated with the Y serotype and X serotype, respectively, and furthermore, the multiplex PCR assays results showed serotypes 2a and 2b, respectively, and the strains were considered to have serotype conversion. The 20 strains carrying the gtrⅡ gene showed multiple nucleotide mutations. Besides 3 strains of 3 amino acid mutations, the amino acid sequences of the other 17 strains showed a stop codon in advance, resulting in functional inactivation of gtrⅡ. PFGE analysis revealed that the similarity between the serotype Y strain carrying the gtrⅡ gene and the serotype 2a strain was 75.8%-100%, and the similarity between the serotype X strain carrying the gtrⅡ gene and the serotype 2b strain was 81.6%-100%. Conclusion: Mutations in the gtrⅡ gene are more complicated in serotype-transforming Shigella flexneri serotype Y or X strains. Molecular typing suggests that the serotype-transforming Shigella flexneri serotype Y or X strains may be derived from the Shigella flexneri serotype 2a or 2b, and advance the serotype conversion to 1949.

[Comparison of colonization ability of O1 and O139 Vibrio cholerae strains on soft-shelled turtle's surface]

Objective: To study the preferred colonization sites of O1 Vibrio cholerae (V.cholerae) and the colonization ability difference for O1 and O139 V. cholerae on soft-shelled turtle's surface. Methods: 8 O1 and O139 V. cholerae strains were obtained from branch of diarrheal diseases, Chinese center for disease control and prevention. 63 soft-shelled turtles weighing 150 g and 9 cm in length (diameter of calipash) were selected for use in the study. The preferred colonization sites and proliferation trend were studied by using bioluminescent imaging method. The colonization factors for O1 V. cholerae strains were studied by constructing colonization gene mutant strains (VC1897dmshA, VC1897dgbpA and VC1897dtcpA), performing competition colonization assays and analyzing the competitive indexes. After pairing off O1 and O139 strains respectively to perform 16 competition groups, the colonization difference of these two strains were studied by competition colonization assays. Results: The colonization sites by V. cholerae on soft-shelled turtles surfaces was clustered. More V. cholerae strains colonized on turtle's calipash and carapace on dorsal side and less strain colonized on ventral side. The competition colonization assays showed that colonization ability of O1 serogroup mshA mutant strains were 7.26 times lower than VC1897dlacZ. Besides, the CI value (O139/O1) of 11 out of the 16 competition groups were greater than 2 (between 2.07 and 59.84). Two groups showed values of 1.43 and 0.93 respectively and 3 groups lower than 0.7. Conclusion: The preferred colonization sites for O1 V. cholerae strains on body surface were observed.MSHA was one of the main colonization factors for its colonization. Our study suggested that in general, O139 V. cholerae strains have stronger colonization ability than O1 strains. Besides, strains isolated from soft-shelled turtles tend to have stronger colonization ability than strains isolated from patients.

[Spatial and temporal clustering characteristics of typhoid and paratyphoid fever and its change pattern in 3 provinces in southwestern China, 2001-2012]

Objective: To analyze the spatial and temporal clustering characteristics of typhoid and paratyphoid fever and its change pattern in Yunnan, Guizhou and Guangxi provinces in southwestern China in recent years. Methods: The incidence data of typhoid and paratyphoid fever cases at county level in 3 provinces during 2001-2012 were collected from China Information System for Diseases Control and Prevention and analyzed by the methods of descriptive epidemiology and geographic informatics. And the map showing the spatial and temporal clustering characters of typhoid and paratyphoid fever cases in three provinces was drawn. SaTScan statistics was used to identify the typhoid and paratyphoid fever clustering areas of three provinces in each year from 2001 to 2012. Results: During the study period, the reported cases of typhoid and paratyphoid fever declined with year. The reported incidence decreased from 30.15 per 100 000 in 2001 to 10.83 per 100 000 in 2006(annual incidence 21.12 per 100 000); while during 2007-2012, the incidence became stable, ranging from 4.75 per 100 000 to 6.83 per 100 000 (annual incidence 5.73 per 100 000). The seasonal variation of the incidence was consistent in three provinces, with majority of cases occurred in summer and autumn. The spatial and temporal clustering of typhoid and paratyphoid fever was demonstrated by the incidence map. Most high-incidence counties were located in a zonal area extending from Yuxi of Yunnan to Guiyang of Guizhou, but were concentrated in Guilin in Guangxi. Temporal and spatial scan statistics identified the positional shifting of class Ⅰ clustering area from Guizhou to Yunnan. Class Ⅰ clustering area was located around the central and western areas (Zunyi and Anshun) of Guizhou during 2001-2003, and moved to the central area of Yunnan during 2004-2012. Conclusion: Spatial and temporal clustering of typhoid and paratyphoid fever existed in the endemic areas of southwestern China, and the clustering area covered a zone connecting the central areas of Guizhou and Yunnan. From 2004 to 2012, the most important clustering area shifted from Guizhou to Yunnan. Findings from this study provided evidence for the identifying key areas for typhoid and paratyphoid fever control and prevention and allocate health resources.

[An outbreak of paratyphoid fever in a county of Yunnan province, 2010-2011]

Objective: To identify the source and to comment on control program regarding an outbreak of paratyphoid A fever in a county, through field studies. Methods: Descriptive epidemiological methods were adopted to describe the epidemiological characteristics of the outbreak, which occurred in Yuanjiang county, Yunan province between 2010-2011, China. Case-control study with environmental investigation was performed to identify related risk factors and pathogens while isolation and susceptibility on the suspected pathogens were conducted. Subsequently, intervention and preventive measures were taken for the control of the outbreak. Results: A total of 600 cases were diagnosed and reported as paratyphoid fever A which spread over the whole Yuanjiang county, including 10 townships with different incidence rates. The disease was spatially clustered and the prevalence rates in these townships decreased with increasing distances from the polluted fields. Data from the case-control study discovered that consumption of raw vegetables was the main risk factor associated with this outbreak of paratyphoid fever (OR=65.3, P<0.001). Management of patients did not meet the requirements while feces and urine of the outpatients polluted the wastewater system in the city. Salmonella paratyphi A isolates were identified from the improperly disinfected wastewaters in hospitals and city systems, respectively. After the measures as prohibiting the planting of vegetables in contaminated fields and disinfection of hospital wastewater were taken, the outbreak subsided. Conclusions: Urban and hospital wastewater used for vegetables irrigation together with the tradition of eating uncooked vegetables seemed responsible for the outbreak of this paratyphoid fever. Intervention programs carried by the local government played a key role in controlling this large outbreak.

Effects of inter-implant distance and implant length on the response to frontal traumatic force of two anterior implants in an atrophic mandible: three-dimensional finite element analysis

The aim of this three-dimensional finite element analysis study was to examine the biomechanical behaviour of dental implants and the surrounding bone under traumatic frontal force. Models were created of an edentulous atrophic mandible using cone beam computed tomography data from a patient; two titanium alloy implants (Ti-6Al-4V) were virtually inserted into the anterior of the mandible. Six different variations were modelled to represent differences in implant location (lateral incisor vs. canine placement) and implant length (monocortical, bicortical, and long-bicortical). A static force of 10 MPa was applied frontally to the symphysis region of each model, and the maximum equivalent von Mises strain of bone, maximum von Mises stress of implants, and chromatic force distributions in bone and implants were recorded. In general, when compared to lateral incisor placement, canine placement of implants resulted in greater von Mises stress on implants and greater equivalent von Mises strain on bone. The findings of the present study showed the distribution of traumatic force to be affected more by inter-implant distance than by implant length. The insertion of implants in the lateral incisor area was found to be a better solution than canine area placement in terms of frontal plane trauma and fracture risk.

Peripheral giant cell reparative granuloma of maxilla in a patient with aggressive periodontitis

Peripheral giant cell reparative granuloma is a reactive and rare lesion of oral cavity with unknown etiology which is derived from periosteum and periodontal ligament and occurs frequently in young adults. Inflammation or trauma is underlying causative factor of reactive proliferation. In the present case report, a 35 year-old male with aggressive periodontitis and peripheral giant cell reparative granuloma is presented. The patient applied to our clinic with a complaining about a big nodule at his palate. The lesion was pedunculated and localized at his right maxilla between #16 and #17 which arose from distal aspect of #16, and the surface of the lesion was hyperkeratotic and the lesion was measured 22 x 30 mm at the largest diameter. He also had severe generalized aggressive periodontitis and hypertension. Amoxicillin clavulanate 625 mg, three times a day, metronidazole 500 mg three times a day and 0.2% chlorhexidine digluconate oral rinse, twice a day for a week, were prescribed to the patient. Then, scaling and root planing were performed along with systemic antibiotic treatment and he scheduled for surgery. The lesion was excised completely and #16 was extracted. After the healing period, periodontal surgery was planned for the treatment of aggressive periodontitis. Obtained tissue specimen was sent for histopathological examination. The diagnosis of peripheral giant cell reparative granuloma was confirmed with histopathological examination. No intra- and post-operative complications were seen.

Completing treatment for latent tuberculosis: patient background matters

BACKGROUND

Treatment of latent infection with Mycobacterium tuberculosis effectively reduces future activation and transmission of tuberculosis. However, patient adherence to preventive treatment influences its effectiveness. Treatment completion is commonly considered as a proxy for adherence.

OBJECTIVE

To identify factors associated with failure to complete preventive treatment.

DESIGN

Data from 415 consecutive patients who started preventive treatment at the Karolinska University Hospital, Stockholm, Sweden, between 2002 and 2007 were collected and treatment completion was evaluated. Patients were classified as 'completers' or 'non-completers'. Association between treatment completion status and patient characteristics was assessed using logistic regression.

RESULTS

Younger patients, patients originating from Somalia and asylum seekers were more likely to be non-completers. The proportion of completers increased from 71% in 2002 to 87% in 2007. However, this trend appears to be caused mostly by an increase in the proportion of European patients.

CONCLUSION

The finding of a low rate of treatment completion among Somalis should be regarded as a call for intervention on the individual patient level, also taking into account socio-cultural aspects such as perceptions of health care by the Somali community. Treatment completion continues to be of concern as it is not improving among risk populations.

A study comparing the efficacy of antimicrobial agents versus enzyme (P-gp) inducers in the treatment of 2,4,6 trinitrobenzenesulfonic acid-induced colitis in rats

The intestinal microflora is an important cofactor in the pathogenesis of intestinal inflammation; and the epithelial cell barrier function is critical in providing protection against the stimulation of mucosal immune system by the microflora. In the present study, therapeutic role of the antibacterial drugs rifampicin and ciprofloxacine were investigated in comparison to spironolactone, an enzyme inducer, in 2,4,6-trinitrobenzenesulfonic acid (TNBS)-induced colitis of the rats. Drugs were administered for 14 days following induction of colitis. All drug treatments ameliorated the clinical hallmarks of colitis as determined by body weight loss and assessment of diarrhea, colon length, and histology. Oxidative damage and neutrophil infiltration as well as nuclear factor κB (NF-κB) and tumor necrosis factor α (TNF-α) expressions that were increased during colitis, were decreased significantly. Rifampicin and ciprofloxacin were probably effective due to their antibacterial and immunomodulating properties. The multidrug resistence gene (MDR1) and its product p-glycoprotein (P-gp) has been implicated in the pathogenesis of inflammatory bowel disease (IBD). In the present study, findings of the P-gp expression were inconclusive but regarding previous studies, it can be suggested that the beneficial effects of rifampicin and spironolactone may be partly due to their action as a P-gp ligand. Spironolactone has been reported to supress the transcription of proinflamatory cytokines that are considered to be of importance in immunoinflammatory diseases. It is also a powerful pregnane X receptor (PXR) inducer; thus, inhibition of the expression of NF-κB and TNF-α, and amelioration of inflammation by spironolactone suggest that this may have been through the activation of PXR. However, our findings regarding PXR expression were inconclusive. Activation of PXR by spironolactone probably also contributed to the induction of P-gp, resulting in extrusion of noxious substances from the tissue.

Autophagy inhibition contributes to radiation sensitization of esophageal squamous carcinoma cells

Radiotherapy is a useful component of treatment strategies for esophageal cancer. The role of autophagy in response to ionizing radiation was investigated in human esophageal squamous carcinoma cells. Cell viability and clonogenic survival assay were used to evaluate the radiosensitivity of autophagy inhibitor (3-MA) on esophageal squamous carcinoma cells. The percentage of apoptotic cells and cell cycle analysis were assessed by flow cytometry; DAPI staining was used to detect apoptotic cells. The expression of beclin-1 and LC3 was measured using a Western blot. The ultrastructural analysis was under the electron microscope. 6 Gy irradiation induced a massive accumulation of autophagosomes accompanied by strong upregulation of beclin-1 and LC3-II expression in TE-1 cells. Compared with radiation alone, 3-MA combined with radiation significantly decreased cell viability, as well as autophagic ratio, beclin-1, and LC3-II protein level. Inhibition of autophagy increased radiation-induced apoptosis and the percentage of G2/M-phase cells. Blockade of autophagy with 3-MA enhanced cytotoxicity of radiotherapy in human esophageal squamous carcinoma cells. It suggests that inhibition of autophagy could be used as adjuvant therapy to treat esophageal squamous cell carcinoma.

Distribution of pathogenic Yersinia enterocolitica in China

Yersinia enterocolitica (1,295 strains) was isolated from diarrhea patients, livestock, poultry, wild animals, insect vectors, food, and the environment. They were studied for epidemiology distribution using bacterial biochemical metabolism tests, their virulence genes, and pulsed-field gel electrophoresis (PFGE) sub-typing. The data showed that 416 of the 1,295 strains were pathogenic, where the pathogenic Chinese isolates were of serotypes O:3 and O:9. These two serotypes were found in livestock and poultry, with swine serving as the major reservoir. The geographic distribution of pathogenic isolates was significantly different, where most of the strains were isolated from the cold northern areas, whereas some serotype O:3 strains were recovered from the warm southern areas. By the analysis of the data of the Ningxia Hui Autonomous Region, we find the phenomenon of 'concentric circle distribution' around animal reservoirs and human habitation. The clustering of PFGE showed that the patterns of the pathogenic strains isolated from diarrhea patients were identical compared to those from the animals in the same area, thus, suggesting that the human infection originated from the animals.

Comparison of automated ribotyping and pulsed-field gel electrophoresis for subtyping of Vibrio cholerae

AIMS

To compare the discriminatory power of an automated ribotyping method for Vibrio cholerae subtyping with the pulsed-field gel electrophoresis (PFGE), to evaluate the possibility of automated ribotyping in use of outbreak investigations and surveillance of cholera.

METHODS AND RESULTS

Eight-one epidemiologically unrelated isolates of V. cholerae, and 19 isolates from seven cholera outbreaks were used as the panels. When comparing the two methods using the epidemiologically unrelated isolates, automated ribotyping using PvuII distinguished 38 different ribotypes with a D-value of 0.8956. When combined with serotyping, the D-value is 0.9466. However, PFGE with NotI and SfiI digestions had higher D-values of 0.9951 and 0.9948, respectively. PFGE could cluster the isolates from each outbreak into the same pattern, and distinguish different patterns from different outbreaks, whereas automated ribotyping had lower discriminatory ability.

CONCLUSIONS

The automated ribotyping has lower discriminatory ability compared to PFGE, and is limited to application in V. cholerae subtyping and outbreak investigation.

SIGNIFICANCE AND IMPACT OF THE STUDY

The study evaluated the limitation in subtyping of automated ribotyping for V. cholerae, and raise the question of improvement for the automated ribotyping in subtyping.

Extensive transmission of an isoniazid-resistant strain of Mycobacterium tuberculosis in Sweden

SETTING

City of Stockholm, Sweden.

BACKGROUND

The incidence of tuberculosis (TB) in Sweden increased by 40% between 2003 and 2005. The spread of a unique TB strain resistant to isoniazid (INH) contributed to this increase.

OBJECTIVE

To describe outbreaks of TB caused by this single strain, elucidate possible causes for its extensive spread and identify shortcomings of the TB control programme in Sweden.

RESULTS

We identified a cluster consisting of 102 culture-confirmed TB cases with identical DNA fingerprints and 26 epidemiologically related cases, not confirmed by culture, all diagnosed between 1996 and 2005. Five partly separate outbreaks of this strain were discovered. Epidemiological links were established for 56% of the culture-confirmed cases and for all cases not confirmed by culture. Three patients died while receiving treatment, four became failures and eight defaulted or were lost to follow-up. Only eight patients received directly observed treatment (DOT) up to a period of 3 months, although 40% had poor adherence.

CONCLUSIONS

Shortcomings of the national TB programme were revealed. Improved contact tracing and case holding, including DOT, is crucial to reduce TB transmission in Sweden.

Dynamic progression of an intraperitoneal xenograft model of human ovarian cancer and its potential for preclinical trials

This study was conducted to establish a feasible intraperitoneal xenograft model in nude mice which mimicked the dynamic progression of human ovarian cancer and to explore its potential for preclinical trials. A human ovarian tumor line SKOV3 was originally injected s.c. to develop tumors; then the tumors were harvested and minced into small particles for i.p. inoculation in three groups of nude mice which would be monitored consecutively. The intraperitoneal carcinomatosis and relevant organs were collected for histopathological dynamic comparison and CA125 immunohistochemical staining 7, 21 and 49 days after inoculation. An additional experiment with cisplatin sensitivity test was performed and tumor tissues were observed for apoptosis-Hoechst assay. The intraperitoneal carcinomatosis had a rapid progression which resulted in extensive dissemination on the peritoneal surfaces and invasion into abdominal lymph nodes, livers, pancreas and spleen. Tumor tissues revealed similar morphological features of primary tumor from which SKOV3 derived and part of in vivo tumor mass was positive for CA125. Cisplatin could significantly inhibit the intraperitoneal carcinomatosis growth. This model may provide a valuable platform to study the biological properties of ovarian cancer as well as to test new therapeutic strategies in preclinical trials.

Humoral and cellular immunity induced by tumor cell vaccine based on the chicken xenogeneic homologous matrix metalloproteinase-2

Matrix metalloproteinase-2 (MMP-2) has been used as a target for cancer immunotherapy. The activation of immunization by breaking immune tolerance to self-MMP-2 may be one of the promising approaches for the treatment of MMP-2-positive tumors. In this study, we constructed the xenogeneic tumor cell vaccine c-MMP-2 by transfecting CT26 and LLC cells with chicken MMP-2 cDNA constructs. MMP-2-specific autoantibodies in sera and tumor cells were found in mice immunized with c-MMP-2. Protection against tumor growth was evaluated in respect of the relative contributions of autoantibodies, CD4+, and CD8+ T cells. Treatment with this vaccine (c-MMP-2) also prolonged the survival time of mice bearing cancer. The specific cytotoxic T-cell responses suggested that the treatment increased CD8+ T-cell activity. The antitumor activity of c-MMP-2 was abrogated by in vivo depletion of CD4+ and CD8+ T-lymphocytes and improved by adoptive transfer of CD4+ and CD8+ T-lymphocytes from the mice treated with c-MMP-2. An alternative DNA vaccination strategy for cancer therapy was identified in this study by eliciting humoral and cellular immunoresponse with a crossreacting transfectant.

Endocarditis and pericarditis complicating pneumococcal bacteraemia, with special reference to the adhesive abilities of pneumococci: results from a prospective study

The incidence of pneumococcal cardiac infections is unknown and the pathogenicity of such complications is poorly understood. In a prospective, international, observational study, eight of 844 patients hospitalised with Streptococcus pneumoniae bacteraemia developed endocarditis (n = 5) or pericarditis (n = 3). The clinical and microbiological characteristics of these patients were compared with those of control patients. The corresponding incidence of pneumococcal endocarditis was c. 1-3/1 million inhabitants/year. There was no common pattern in the medical history of patients with an infectious cardiac complication. The severity of illness upon admission was comparable with that for patients without infectious cardiac complications, as was the 14-day mortality rate (25% and 17%, respectively). For encapsulated S. pneumoniae, no significant differences were found between patients with infectious cardiac complications and controls in adherence assays. However, non-encapsulated S. pneumoniae showed higher hydrophobicity and increased adherence to human epithelial cells.

Structural characterization of T-protein of the Escherichia coli glycine cleavage system by X-ray small angle scattering

T-protein, one of the components of the glycine cleavage complex, catalyses the formation of ammonia and methylene-tetrahydrofolate from H-protein-bound intermediate. Native T-protein of the glycine cleavage system from E. coli was efficiently purified using a combination of hydrophobic interaction, gel permeation and ion exchange chromatography. Synchrotron radiation small angle X-ray solution scattering indicates that T-protein has an extended structure in solution. A low resolution model of the protein was constructed ab initio and tentative models of the tertiary structure were built using prediction methods constrained by the scattering data.

Induction of apoptosis by norcantharidin in human colorectal carcinoma cell lines: involvement of the CD95 receptor/ligand

PURPOSE

Cantharidin, a natural toxin, is the active substance of mylabris and has antitumor effects in man. Norcantharidin, the demethylated analogue of cantharidin, has been used in the treatment of patients with primary hepatoma and those with leukopenia in China. The present study was designed to investigate whether norcantharidin exerts cytotoxic activity against colorectal cancer cells by inducing apoptosis and to examine the possible mechanism in the phenomenon.

METHODS

Inhibition of proliferation of norcantharidin on Colo205, HT-29, and SW480 colorectal cancer cells was determined by the trypan blue dye exclusion test. Apoptosis of norcantharidin-treated cells was determined by morphological analysis, agarose gel DNA electrophoresis, and quantitated by flow cytometry after staining with propidium iodide. Cell cycle and the cell surface expression of the CD95/CD95 ligand were evaluated by flow cytometry. Caspase 8-like protease and protein phosphatase 1 and 2A activities were also analyzed.

RESULTS

Treatment with norcantharidin of colorectal cancer cells not only inhibited cell proliferation, but also induced apoptosis. Norcantharidin induced apoptosis mainly in two phases: rapid apoptosis in S-phase cells and delayed apoptosis in G2/M arrested cells. Treatment with norcantharidin resulted in an upregulation of the CD95 receptor and CD95 ligand on the cell surface. Furthermore, stimulation with anti-CD95 monoclonal antibody (mAb) resulted in further induction of apoptosis after treatment with norcantharidin. In addition, the apoptosis-inducing effect of norcantharidin was almost completely inhibited by anti-CD95 ligand mAb. Norcantharidin-treated cells showed the activation of caspase 8. Both zVAD-FMK (a broad range caspase inhibitor) and IETD-FMK (a caspase-8 inhibitor) showed apparent inhibition of the apoptosis-inducing effect. Norcantharidin did not show an inhibitory effect on protein phosphatase.

CONCLUSIONS

These results suggest that norcantharidin triggers apoptosis in colorectal cancer cell lines via the activation of the CD95 receptor/ligand system, and that this agent may be useful for developing new therapeutic regimens for the treatment of colorectal carcinoma.

[Primary analysis and sequencing the hemolytic relative gene of Edwardsiella tarda]

Hemolysin is an important pathogenic agent of Edwardsiella tarda (ET). A fragment containing hemolytic gene, of which sequence is 4,264 bp, was cloned from ET-12 chromosome by shutgun method. It has no similarity to the hemolysin genes reported, of which 424 bp of open read frame (ORF) 3 has 68% similarity to the hemolysin regulatory gene of S. typhi (slyA). The subclone which has complete ORF3 was hemolytic, and the other of which Kanamycin gene was inserted in Pvu I of ORF3 was no hemolytic. It proved the gene was in chromosomes of ET-12 and the other ET strains by hybridization in situ and Southern blot. As recombination plasmid with the gene entered nonhemolytic ET by electroporation, no hemolytic phenomenon was observed. Conclusion was that the gene wasn't the hemolysin gene and was hemolytic relative gene.

[Anti-tumor immune response against mouse melanoma to xenogeneic vaccination]

OBJECTIVE

To study the inhibition of melanoma growth in mice by vaccination with xenogeneic melanocytes.

METHODS

Xenogeneic vaccine was prepared from pig eye melanocytes. It was used before or after B16 melanoma challenge in C57 mice. The size of tumor was monitored. Cytotoxic T lymphocyte (CTL) activity of mouse spleen cells was measured by 51Cr release assay. Antibody response against pig melanocytes and B16 melanoma cells were detected by indirect ELISA.

RESULTS

Preventive vaccination resulted in inhibition of tumor growth in 90% of the immunized mice, while therapeutic vaccination inhibited tumor growth in 50% of the treated mice. Specific CTL activity and antibodies in the immunized mice were detected.

CONCLUSION

Anti-tumor immune response capable of inhibiting melanoma growth can be induced by xenogeneic melanocyte vaccination.

[Quantification analysis of vascular endothelial cells in human solid tumor]

Angiogenesis is essential for the growth and metastasis of solid tumors. Intratumoral microvessel count, which represents a measure of tumor angiogenesis, has been associated with prognosis of patients with a variety of malignancies. But till now, it is still a problem to quantitate the angiogenesis of tumors exactly. In this study, the endothelial cells in 20 solid tumors were conjugated with anti-CD34 monoclonal antibodies labelled with red-fluorescent substances, and were observed by fluorescence microscopy and quantitated by flow cytometry. The results of flow cytometry were analysed by t-test. The correlation was analysed between percentage of flow cytometry and vessel counts (light microscopy, x 200) in each tumor which was stained with anti-CD34 monoclonal antibodies and anti-VIII factor related antigen polyclonal antibodies by using immunohistochemistry. The results showed there was significant difference between the treatment group and control group in flow cytometry, and a significant correlation between the endothelial cells percentage by flow cytometry and the vessel counts by immunohistochemistry was observed, although the average vessel counts were approximately three times with CD34 staining as much as with VIII factor related antigen staining. These data indicate that flow cytometry as a novel method can quantitate angiogenesis of tumors exactly and quickly.

[The relationship of cellular DNA content with clinical stage and biological features of colorectal cancer]

The purpose of this study was to explore the relationship of cellular DNA content with clinical stage and biological features of cancer. Flow cytometry was performed on fresh specimens from 86 patients from 1997 to 1998. Forty-five (53.3%) specimens were found to contain cells with abnormal DNA (DNA nondiploidy). Although none of the sex, age, site, differentiation variables correlated with flow cytometric DNA ploidy, nondiploidy was associated with Dukes' stage and lymph node metastasis. Duke's A stage tumors were more frequently diploid than were more advanced tumors, but no difference between Duke's B, C and D stages were observed. These findings suggest that ploidy is associated with some pathological factors.

Heme-regulated eIF-2alpha kinase purifies as a hemoprotein

The regulation of protein synthesis by the availability of heme in reticulocytes is well established. However, the mechanism by which heme regulates translational initiation is not clear. In this study, we have examined the heme regulation directly on the homogeneous heme-regulated eIF-2alpha kinase (HRI), which is activated during heme deficiency. We found that HRI purified as a hemoprotein with the characteristic Soret band of hemoprotein at 424 nm. This HRI was an active autokinase and eIF-2alpha kinase, and its kinase activities were inhibited by submicromolar concentrations of hemin with an apparent Ki of 0.5 microM. Homogeneous HRI was a homodimer, and its activities could not be inhibited by incubation with purified inactive K199R HRI in vitro. Our results suggest that there are two distinct types of heme-binding sites in the HRI homodimer. The binding of heme to the first site is stable, while the binding of heme to the second site is responsible for the rapid downregulation of HRI activity by heme. These results indicate that HRI binds heme and serves as a sensor of the availability of heme to coordinate the balanced synthesis of globins and heme in erythroid cells.

[Detecting expression of the multidrug resistance gene product (P170) in human tumor tissues and cells by flow cytometry]

We have detected the human multidrug resistance gene (MDR1) product P170 in 29 solid tumor samples and K562 cell line through indirectimmunoflourence staining by flow cytometry using mouse monoclonal antibody (McAb). The results showed that the expression of P170 was detected in 18 samples, the positive ratio being 62.1%; the expression was not detected in 11 samples, the negative ratio being 37.9%; and 99.9% of K562 cells expressed P170. In 16 of the 18 positive samples, the percent ratio of tumor cells for expression of P170 was less than 30%; in the other 2, more than 30%. This indicated that the positive ratio of P170 of most tumor samples was high, but their percent ratio of P170 was low. Thus it provided a parameter for reference in evaluating the efficacy of clinical antitumor treatments.

Evidence for the presence of muscarinic M2 and M4 receptors in guinea-pig gallbladder smooth muscle

1. The affinities of 10 selective muscarinic receptor antagonists against [3H]-quinuclidinyl benzilate (QNB) binding were determined to characterize the muscarinic receptors present in guinea-pig gallbladder smooth muscle. The highest correlation was obtained for the comparison between the pKi values for the gallbladder smooth muscle and M2 sites. Pirenzepine revealed two binding sites with affinities indicating the presence of muscarinic M2 receptors in abundance and a minor population of an additional site(s). 2. Carbachol produced gallbladder contractions, stimulated phosphoinositide (PI) hydrolysis and inhibited cAMP formation concentration-dependently with pD2 values of 6.12 +/- 0.11, 5.18 +/- 0.33 and 7.19 +/- 0.15, respectively. 3. Pirenzepine, 4-DAMP, HHSiD, pF-HHSiD, AF-DX 116, methoctramine, AQ-RA 741, guanylpirenzepine and AF-DX 384 showed competitive antagonism against carbachol-induced gallbladder contractions. There was no correlation between the pA2 values for the gallbladder and pKi values for the M2 sites, whereas significant correlations were found for the M1, M3 and M4 sites, the best correlation being between the pA2 values for the gallbladder and M4 subtypes. 4. Finally, the presence of both m2 and m4 receptor proteins were demonstrated by Western blot analysis. It is concluded that guinea-pig gallbladder smooth muscle has both muscarinic M2 and M4 receptors, which are coupled to adenylate cyclase inhibition and PI hydrolysis. 5. Although it seems likely that M2 receptors do not play a primary role in carbachol-induced guinea-pig gallbladder contraction, the characterization of the muscarinic subtypes which mediate these contractile responses needs further evidence.

Detection of circulating antigen by McAb-AST for evaluating the efficacy of anti-Leishmania chemotherapy

We have adapted the simple and sensitive McAb-antigen spot test (AST) for evaluating the efficacy of anti-Leishmania chemotherapy. Serum samples from 37 kala-azar patients were tested by McAb-AST, and all showed definite positive reactions before treatment. After a course of antimony treatment, 20 turned negative, coupled with the disappearance of clinical symptoms; another 12 cases responded with weak positivity accompanied by an improvement of clinical manifestations; and the remaining 5 antimony-resistant patients showed strong positive reactions, with their conditions gradually worsening. Furthermore, all 6 cases in which the diagnosis was missed by the bone marrow smear method turned McAb-AST negative after chemotherapy. These results suggest that McAb-AST can be used to evaluate the efficacy of chemotherapy as well as to avoid missed diagnosis by the bone marrow smear method.

[Studies on protective monoclonal antibodies to Leishmania donovani]

Kala-azar is increasing in incidence in some endemic areas of China, such as provinces of Sichuan and Gansu. Monoclonal antibodies have been shown to interfere with the cutaneous leishmaniasis infection in the experimental animals. We have now raised McAb against membrane antigen of promastigotes of L. donovani canine isolate (the pathogen of visceral leishmaniasis). In this paper we report 3 McAb which inhibit the growth of promastigotes in vitro culture by incorporation of 3H-thymine deoxyriboside, such as McAb 2B12-A8, 2H6-E3, in the presence of complement, showing strong inhibiting effects with a decrease in incorporation of 3H-TdR, 94-99.3% rate of inhibition, whereas the inhibition rate induced by McAb 1B1-C2 fluctuated in a range of 68-95%, which is identical with the results of macrophage infection inhibition test by the same McAb, 61-87%. The results of ultrastructural localization of L. donovani antigen by protective McAb 2H6-E3 with immunogold technique showed the gold particles, in clumps, widely distributed on the outer side of promastigotes membrane. According to the high density of localized gold particles, it is suggested that this antigen is abundant on the plasma membrane.

Role of reversing factor in the inhibition of protein synthesis initiation by oxidized glutathione

The inhibitions of protein synthesis initiation in heme-deficient reticulocyte lysates and in GSSG-treated hemin-supplemented lysates are both characterized by the activation of heme-regulated eIF-2 alpha kinase, which phosphorylates the alpha-subunit of eukaryotic initiation factor (eIF-2). In both inhibitions, the accumulation of eIF phosphorylated in alpha-subunit (eIF-2(alpha P)) leads to the sequestration of reversing factor (RF) in a phosphorylated 15 S complex, RF.eIF-2(alpha P), in which RF is nonfunctional. A sensitive assay for the detection of endogenous RF activity in protein-synthesizing lysates indicates that, in GSSG-inhibited (1 mM GSSG) lysates, RF is more profoundly inhibited than in heme-deficient lysates. RF inactivation in GSSG-induced inhibition appears to be due to two separate but additive effects: (i) the formation of the phosphorylated 15 S RF complex, RF.eIF-2(alpha P), and (ii) the formation of disulfide complexes which inhibit RF activity. Both inhibitory effects are overcome by catalytic levels of exogenous RF which permits the resumption of protein synthesis. RF activity and protein synthesis in GSSG-inhibited lysates are efficiently restored by the delayed addition of glucose-6-P or 2-deoxyglucose-6-P (1 mM). The rescue of protein synthesis by hexose phosphate (1 mM) is proportional to the extent of RF recovery and is due in part to NADPH generation; even at levels of hexose phosphate (50 microM) too low to support protein synthesis, partial restoration of RF activity occurs due to increased NADPH/NADP+ ratios. The ability of dithiothreitol (1 mM) to restore RF activity in GSSG-treated but not heme-deficient lysates also provides evidence for a reducing mechanism which functions at the level of RF. The results suggest that NADPH plays a role in the maintenance of sulfhydryl groups essential for RF activity.

High pO2-activated inhibitor of protein synthesis in rabbit reticulocytes: its relationship to glutathione disulfide-induced inhibitor and to a approximately 23,000-Mr sulfhydryl protein

The treatment of reticulocyte post-ribosomal supernatant containing ribosome wash with high pO2 or glutathione disulfide resulted in the activation of an inhibitor of protein synthesis of approximately 23,000-Mr as implicated by its elution from Sephadex G-100. This inhibitor could also be directly activated by exposure of the approximately 23,000-Mr fractions of the control eluate to high pO2 or glutathione disulfide. The high pO2-dependent activation of the inhibitor was blocked by the presence of glucose-6-phosphate or cAMP (2 mM). The inhibitor was stable (and activable) during a 5 minute incubation at 80 degrees C. The analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis of the G-100 (approximately 23,000-Mr) fractions treated with [14C]N-ethylmaleimide revealed the abolishment of the label in a approximately 23,000-Mr protein band in parallel to high pO2-dependent inhibitor activation.

A translational inhibitor activated in rabbit reticulocyte lysates under high pO2

An inhibitor of protein synthesis was activated under high oxygen partial pressure (pO2) in hemin-supplemented and glutathione disulfide-free lysates from rabbit reticulocytes. This inhibitor shared some common features with other translational inhibitors from rabbit reticulocytes; that is, hemin-controlled repressor, glutathione disulfide-activated inhibitor and high pressure-activated inhibitor. It caused biphasic kinetics of inhibition which could be potentiated by ATP. Its activation was prevented by cAMP or glucose 6-phosphate. The high pO2-inhibitor could be partially purified from post-ribosomal supernatant containing ribosomal salt wash by precipitation between 0-50% (NH4)2SO4-saturation, Sephadex G-100, and DEAE-cellulose chromatography.

High salt effect on RNA synthesis in Krebs ascites tumor cells

The incubation of Krebs ascites tumor cells in medium with a high salt concentration resulted in a partial inhibition of nuclear RNA synthesis. The residual RNA polymerase activity in such nuclei was only slightly inhibited by low concentrations (50 nM) of alpha-amanitin. This finding suggested an inhibition of RNA polymerase II activity under conditions of medium hypertonicity. Indeed, RNA polymerase II, isolated from the nuclei of cells exposed to hypertonicity, revealed only half of the control activity. On the other hand, RNA polymerase I was not affected by hypertonicity. Moreover, chromatin fractions isolated from cells incubated in hypertonic or isotonic medium were equally template-active in RNA synthesis.