Site of transcriptional activation of virB on the large plasmid of Shigella flexneri 2a by VirF, a member of the AraC family of transcriptional activators

VirB plays a central role in the regulation of virulence of Shigella flexneri. It acts as a transcriptional activator and is itself transcriptionally activated by another virulence protein, VirF. Experiments were performed in order to identify the site upstream of virB at which VirF binds in order to activate transcription. Progressive 5' deletions of the DNA upstream of the transcription start point of virB were constructed by subcloning and Bal31 deletion. These deletion derivatives were cloned into the chloramphenicol acetyltransferase (CAT) reporter gene plasmid pKK232-8 and the resulting plasmids were analysed using a CAT activity assay. This allowed identification of minimal regions required for VirB promoter activity and regions required for full enhancement of promoter activity by VirF. A region approximately 100 bp upstream from the transcription start point of virB was identified as being necessary for full activation of this promoter by VirF. This region encompasses at least one inverted repeat which may play a role in transcription repression in the absence of the activator protein, VirF.

Molecular analysis of the hsp (groE) operon of Leptospira interrogans serovar copenhageni

A chromosomal gene library of Leptospira interrogans serovar copenhageni strain Wijnberg was constructed in phage lambda gt11. Plaque immunoassay with R alpha P64 antiserum identified one clone expressing a putative groEL homologue. DNA sequence analysis of the 2.4 kb EcoRI-Bam HI cloned fragment from strain Wijnberg revealed two open reading frames encoding polypeptides of 10.5 kDa (Hsp10) and 58 kDa (Hsp58). Sequence comparison of the deduced amino acid sequences of these ORFs confirmed the operon as the groE equivalent of Leptospira. Transcriptional analysis suggested that this operon is primarily under the control of an E sigma 70 promoter element. However, both Hsp10 and Hsp58 were overexpressed under heat-shock conditions as determined by [35S]-methionine pulse labelling experiments. As no functional heat-shock promoter could be identified, a 9bp inverted repeat, located between the transcription and translation start sites, may play a role in the upregulation of this operon under heat-shock conditions, similar to mechanisms described for several Gram-positive organisms.

High-resolution computed tomography of the chest: current indications

High-resolution computed tomography (HRCT) may show parenchymal abnormalities in patients with normal or questionable findings on the chest radiograph; and because it provides an accurate assessment of the pattern and distribution of lung disease, it also improves the accuracy of the differential diagnosis. HRCT may be able to distinguish areas of potentially reversible disease from irreversible fibrosis and be a helpful guide to the optimal type and site of lung biopsy. This review summarizes the current indications for HRCT of the chest in the assessment of patients with acute lung disease, chronic infiltrative lung disease, pneumoconiosis, bronchiectasis, and emphysema.

Molecular analysis of the aroA gene of Pasteurella multocida and vaccine potential of a constructed aroA mutant

The aroA gene from Pasteurella multocida was cloned by complementation of the Escherichia coli aroA mutant AB2829 with a DNA library constructed in pUC18. The nucleotide sequence of the P. multocida aroA gene indicated an open reading frame encoding a protein of 441 amino acids, which showed a high degree of homology with the amino acid sequences of various other bacterial AroA proteins. The cloned P. multocida aroA gene was inactivated by insertion of a kanamycin-resistance gene and reintroduced by allelic exchange into the chromosome of P. multocida using the suicide vector pJM703.1. The P. multocida aroA mutant was highly attenuated in a mouse model. Mice immunized intraperitoneally with two doses of live P. multocida aroA mutant were completely protected against a lethal parental strain challenge.

A high-risk community study of paternal alcohol consumption and adolescents' psychosocial characteristics

A prospective community study looked at drinking behavior and biopsychosocial correlates of adolescents (in years 9 and 10 and again in years 11 and 12 at 23 high schools) and their parents. Heavy drinkers were compared to nil/low drinkers. Sons were more likely to drink heavily if fathers drank heavily and mothers who drank heavily were more likely to cohabit with heavy drinkers. Differences in psychological characteristics and home environment were defined in regard to heavy drinking fathers and drinking sons. Difficulty in settling disagreements and reduced time spent with family were the main correlates associated with drinking by both boys who did not necessarily have a heavy drinking father and those who did.

High-resolution computed tomography of drug-induced lung disease

In order to determine the potential clinical utility of high-resolution CT (HRCT) in the assessment of drug-induced lung disease, we reviewed the chest radiographs and HRCT scans of 23 patients and five normal controls. The radiographs and HRCT scans were reviewed separately in random order by two independent observers who were not aware of the relative numbers of patients and controls. Abnormal findings were detected in the affected patients in 17/23 radiographs compared to 23/23 HRCT scans. The patients included five cases of bleomycin toxicity, five cases of nitrofurantoin toxicity, two cases each of penicillamine, busulphan, BCNU and amiodarone toxicity, and one case each of cyclophosphamide, procainamide, mitomycin and methotrexate toxicity. The HRCT appearances could be grouped into four categories according to their dominant pattern and distribution of disease. These include fibrosis with or without consolidation (n = 12), ground-glass opacities (n = 7), widespread bilateral consolidation (n = 2), and bronchial wall thickening with areas of decreased attenuation (n = 2). The results of this study indicate that HRCT is more sensitive than the radiograph in the detection of drug-induced lung disease. The appearances demonstrated by HRCT reflect the pathological mechanisms of drug-induced lung disease.

High-resolution CT of bronchioloalveolar carcinoma

Bronchioloalveolar cell carcinoma has a wide spectrum of pathologic and radiologic appearances. Some of the radiologic features are characteristic enough to suggest the underlying pathologic changes. This article illustrates the various manifestations of bronchioloalveolar cell carcinoma on high-resolution CT (1.5-mm collimation reconstructed with a high-spatial-frequency algorithm). Correlations between the CT and pathologic findings are included.

Trypanosoma brucei mitochondrial ribosomal RNA synthesis, processing and developmentally regulated expression

The steady-state levels of the mitochondrial ribosomal RNAs of Trypanosoma brucei are repressed in the early bloodstream developmental stage of the parasite and accumulate approximately 30-fold during differentiation to the stage found in the midgut of the insect vector. In order to determine the mechanism regulating this developmental process, we have examined the transcription and processing of the 9S and 12S mitochondrial rRNAs of T. brucei. A short-lived RNA was detected in pulse labeling experiments which contains the mature 12S and 9S rRNAs and at least 1200 nucleotides of RNA transcribed from upstream of the 12S rRNA gene. This putative processing precursor RNA was identified in both intact cells and in run-on experiments using isolated mitochondria. The transcripts containing the upstream sequences are unstable and reach isotopic equilibrium within 15 min. Mature rRNAs in the insect developmental stage are stable and show no detectable turnover during a 36-h chase. Comparison of rRNA synthesis in bloodstream and insect life-stages indicates that mitochondrial rRNA levels are controlled not at the transcriptional level, but rather by a mechanism which likely modulates the stability of the mature rRNAs. These results suggest that a short-lived rRNA precursor is synthesized and processed at comparable rates in both bloodstream and insect stages of the parasite. Thus, it appears that differential stability of the mature 9S and 12S rRNAs plays a major role in modulating mitochondrial gene expression during the developmental cycle of T. brucei.

Molecular Biology of African Trypanosomes: Development of New Strategies to Combat an Old Disease

African trypanosomes are protozoan parasites that cause a number of diseases of man and domesticated animals in large regions of sub-Saharan Africa. The diseases have proven to be particularly difficult to prevent or to effectively treat due to features of both the trypanosome and the insect vector, the tsetse fly. The habitat of the tsetse and its resistance to insecticides have rendered vector control efforts ineffective. Attempts to develop a vaccine against the African trypanosomes has been dwarfed by the parasite's ability to change the composition of its exposed surface antigens. This process of antigenic variation allows the parasite to avoid the host's immune response and presents the host with a seemingly endless antigenic repertoire. Since conventional approaches to the control of African trypanosomiasis have largely met with failure, there has been a renewed interest in identifying novel aspects of the biology, biochemistry, and molecular biology of trypanosomes that might be exploited to develop new targets for vaccines or chemotherapy. Importantly, this research has opened a virtual Pandora's box of exciting biochemical and molecular surprises, which makes the African trypanosomes not only important medical pathogens but also an exciting experimental system for the basic scientist. In this review, the authors will describe some of the most recent and intriguing developments in the field of molecular parasitology.

Comparison of diagnostic procedures for porcine leptospirosis

Kidneys and matched serum samples were obtained from 368 pigs slaughtered at three Victorian abattoirs, and originating from 42 farms. Macroscopic lesions (white spots) were observed on 102 of the kidneys. Serum samples were tested by the microscopic agglutination test (MAT) and by an IgM enzyme immunoassay (EIA). Kidneys were cultured for leptospires, examined histologically after Warthin-Starry silver staining and after immunogold silver staining (IGSS), and tested for leptospiral DNA by DNA hybridization. Forty-four infected pigs were identified by culture or immunogold silver staining of kidneys or by high MAT titres (greater than or equal to 1024). Infection was demonstrated in 7.5% of visibly normal kidneys, in 23.5% of kidneys with white spots, and in 48% of kidneys with large white spots, of 1 cm diameter or greater. The apparent (maximum) sensitivities of diagnostic procedures for detecting infection were as follows: MAT (at a titre of either 64 or 1024) 95%; IgM EIA 82%; culture 61%; presence of white spots 55%; IGSS 52%; presence of large white spots 30%; Warthin-Starry silver staining 20%. IGSS, Warthin-Starry staining and DNA hybridization all appeared to be highly specific. Of 22 kidney sections identified as positive by IGSS, 13 showed intact leptospires, and these kidneys were all culture-positive. Nine others showed leptospiral antigen in the kidney tubules but no intact leptospires. Only five of these kidneys were culture-positive.

A purified stage-specific 31 kDa antigen as a potential protective antigen against Ostertagia circumcincta infection in lambs

The 31 kDa antigen of third-stage (L3) Ostertagia circumcincta larvae was evaluated as a potential prophylactic antigen by an analysis of the protective, humoral and cell-mediated responses of lambs immunized with this antigen. Six lambs were immunized by subcutaneous injection with a total of 400 micrograms of the purified 31 kDa antigen in 250 micrograms ml-1 Quil A adjuvant. Five sheep given identical injections but without the 31 kDa antigen were used as controls. All animals were challenged with 4.2 x 10(4) infective L3 O. circumcincta larvae 1 week after the last booster injection. The protection afforded by the 31 kDa antigen was demonstrated by a significant reduction in faecal egg counts (p less than 0.05) and total worm counts (p less than 0.005) in vaccinated animals. Elevated ELISA antibody levels specific to the 31 kDa antigen were detected in the sera of vaccinated animals as early as 3 weeks after immunization. Specific antibodies were further demonstrated by Western blot 4 days after the first booster immunization at 3 weeks. In control animals no antibodies to the 31 kDa antigen were detected in Western blots throughout the course of the experiment. Immunized lambs had significantly higher in vitro lymphocyte stimulation indices (p less than 0.05) than control animals. In haematoxylin and eosin stained sections taken at necropsy from vaccinated sheep, compared with control lambs, there were more larvae present in the crypts of the abomasal epithelium and these larvae were surrounded by lymphocytes and eosinophils. In vaccinated lambs a marked infiltration of lymphocytes in the lamina propria and oedema in the submucosa were also observed.(ABSTRACT TRUNCATED AT 250 WORDS)

Time trends of haemoglobin levels and anaemia prevalence in infancy in a total community

In order to determine the trends in haemoglobin (Hb) levels and the prevalence of anaemia in infancy in an entire community, 3,147 infants aged 9-11 months attending the Mother and Child Health Clinics of the teaching and research Health Center in Kiryat Hayovel, Jerusalem, were examined. From 1971 to 1979 infants diagnosed as anaemic were given treatment. From 1980 to 1988 supplement was given to all infants from the age of 3 to 12 months. There was a mean increase of 0.6 g/dlHb between the two periods, with a larger increase in the Hb levels in 1980-88 as compared to 1971-79 (P = .0001). The prevalence of anaemia less than 11 g/dlHb decreased from 36% in 1971 to 27% in 1979 and to 19% in 1988. The prevalence of anaemia less than 10 g/dlHb decreased from 13.7% in 1971 to 8.7% in 1979 and to 3.6% in 1988. The time trend is probably due to changes in the socio-demographic characteristics of the population, an overall change in infant feeding practices in relation to iron source and the supplementation programme.

Antigens recognized by the human immune response to severe leptospirosis in Barbados

Serum samples obtained from patients hospitalized in Barbados with severe leptospirosis were tested by the microscopic agglutination test (MAT), enzyme immunoassay (EIA) and immunoblotting with leptospires that had been isolated from these patients. While serum samples taken a few days after onset of symptoms often showed no apparent correlation between MAT and EIA, later sequential serum samples produced similar profiles in both tests during the course of infection. Immunoblotting sonicate from Leptospira interrogans serovars arborea, copenhageni and bim with patients' sera, revealed reactions with a number of bands that corresponded with outer envelope components. These components included lipopolysaccharide (LPS), flagella and other outer membrane proteins, in addition to a low-molecular-weight (MW) carbohydrate cross-reactive with members of the Leptospiraceae. IgM antibodies elicited in the first to second week after infection reacted mainly with LPS and the low-MW cross-reactive carbohydrate. Comparative analysis of isolates of the same serovar by sodium dodecyl sulphate polyacrylamide gel electrophoresis and immunoblotting showed that while two serovar arborea isolates were identical, serovar bim isolates differed significantly from each other. This difference was also observed in comparative MAT testing.

Effect of otitis media on development: a community-based study

Otitis media history until age 3 years were recorded for 233 children as part of the surveillance in a Community Program for Promotion of Growth and Development (PROD) conducted in a western neighborhood of Jerusalem. Recurrent otitis media (6 or more episodes) occurred more frequently among children who were of North African or Asian origin, of lower social class and maternal education, and whose duration of breast feeding was less than 26 weeks. Children with recurrent otitis media also failed the 7-month hearing test more frequently than other children. The mean Developmental Quotient score at 2 years and the mean Stanford Binet score at 3 years were statistically significantly lower among children with recurrent otitis media, even after controlling for maternal origin and length of breast feeding. These findings underscore the importance of early identification and early intervention for otitis media.

Molecular analysis of a Leptospira borgpetersenii gene encoding an endoflagellar subunit protein

A flagellin gene, flaB, from Leptospira borgpetersenii (formerly L. interrogans) serovar hardjo was cloned and expressed in Escherichia coli. Expression of the 32 kDa FlaB protein was dependent upon the lacZ promoter from pUC18. Nucleotide sequence data showed an open reading frame encoding 283 amino acid residues, corresponding to a protein of molecular mass 31.3 kDa. The G + C content of the flaB gene was 54.7 mol%. Comparison of the deduced FlaB amino acid sequence with flagellins from other bacteria revealed a high level of identity with the Treponema pallidum FlaB proteins.

Evidence of phenotypic dichotomy within an individual Pasteurella multocida type strain and among some haemorrhagic septicaemia-causing field isolates

Haemorrhagic septicaemia-causing strains of Pasteurella multocida were identified by a disease-specific ELISA. Some strains, however, were of the same serotype as those which cause haemorrhagic septicaemia (HS) but were negative when tested in the disease specific ELISA. The suspect false negative isolates were passaged in mice and retested in the HS ELISA with the same result. Immunoelectron microscopy was used to examine further these suspect HS-causing strains. Monoclonal antibodies and protein A-gold showed that the suspect negative organisms were a mixture of phenotypes with less than 10 per cent, and usually less than 2 per cent, of the population expressing HS-associated epitopes. The degree of staining on the organisms expressing the HS-epitopes was of the same intensity as the positive control organism. Expression of the HS-associated epitopes is presumably too low to allow detection in the current HS ELISA.

Proteins and antigens of Pasteurella multocida serotype 1 from fowl cholera

The protein profiles of Pasteurella multocida serotype 1 isolates and the response of chickens to serotype 1 antigens were investigated using SDS-PAGE. Patterns obtained with Coomassie blue staining of soluble protein extracts were similar. The major difference between isolates was the position of one of the major proteins in the 34-38 kDa region. When chickens were experimentally infected with a clinical isolate of P. multocida serotype 1 various proteins were recognised by immunoblotting, including one with a relative molecular weight of 34 kDa; however, no reactions were observed in the region where LPS is known to migrate. When these infection sera were used in an EIA with purified LPS obtained from Heddleston serotype 1 type strain (X-73) they reacted strongly. Serum used for serotyping isolates in the gel diffusion precipitin test recognised many antigens in common with sera from infected birds, but some antigens were specific to typing sera.

Temperature-regulated expression of invasion genes in Shigella flexneri is controlled through the transcriptional activation of the virB gene on the large plasmid

The invasion phenotype of shigellae is subject to thermoregulation that is known to be expressed through activation of some invasion (inv) genes such as ipaB, ipaC, and ipaD encoded by the large virulence plasmid of Shigella flexneri. The expression of ipa genes is regulated positively by virF through the activation of virB on the plasmid. To identify the mediator for the thermoregulation of the large plasmid, we have studied the effect of temperature on the transcription of virF and virB genes and ipa and the other two inv operons. The results showed that transcription of virB was affected by temperature more strictly than that of virF. Analysis of the mRNA level of virB at different levels of virF transcription indicated that virB transcription depended upon both temperature and virF. On the other hand, transcriptions of ipa and the other two inv operons depended on the activation of virB transcription but not on temperature. By inducing virB transcription from a tac promoter fused with the virB region, invasion ability was restored to a virF-deletion mutant at 30 degrees C as well as at 37 degrees C. By using conditions in which the temperature-dependent expression of the invasion phenotype was circumvented by the induction of virB transcription, intercellular spreading ability in a virF+, virB::Tn5 strain was shown to be expressed even at 30 degrees C. These results suggest that the virB transcription stage is the main target for the thermoregulation.

Opsonic monoclonal antibodies against lipopolysaccharide (LPS) antigens of Pasteurella multocida and the role of LPS in immunity

A panel of six monoclonal antibodies (MAbs) produced from mice immunized with Pasteurella multocida (M1404) (Heddleston serotype 2) reacted with homologous lipopolysaccharide, as indicated by enzyme immunoassay and immunoblotting. All six MAbs reacted with serotypes 2 and 5 of the 16 Heddleston serotypes. The reactive epitopes were localized on the bacterial cell surface by immunogold labelling. The antibodies could agglutinate P. multocida only if cells were first treated with 1 N HCl. All six MAbs opsonized P. multocida for phagocytosis by mouse macrophages but were not bactericidal in the presence of complement. They afforded only partial protection against infection in mice. The results, together with those of active immunization experiments with LPS, suggest a subordinate role for LPS in protection from experimental infection in mice.

Vaccination of mice with lipopolysaccharide (LPS) and LPS-derived immuno-conjugates from Leptospira interrogans

Mice were vaccinated with lipopolysaccharide (LPS) from Leptospira interrogans serovar pomona or hardjo, or with the polysaccharide (PS) fraction of the LPS, or with an immunoconjugate of PS and diphtheria toxoid (DT). Maximum agglutinin titres were found 6-10 weeks after vaccination with LPS or PS-DT conjugate; the latter elicited antibody titres at least 10 times higher than those produced in response to LPS. Animals failed to react significantly to PS. Titres elicited by antigens of serovar pomona were higher than those elicited by serovar hardjo.

Purification and characterization of a protein antigen from Leptospira interrogans serovar hardjo, common to a wide range of bacteria

A protein with a molecular mass of 64 kDa (P64) from Leptospira interrogans serovar hardjo was partially purified by using successively, phase partitioning with Triton X-114, ion-exchange chromatography and sucrose gradient centrifugation. Purification to homogeneity was obtained by electroelution of P64 from SDS-polyacrylamide gels. Monospecific rabbit antiserum (R alpha P64) was prepared using the purified protein preparation. P64 had a native molecular mass of greater than 670 kDa and was recognized by R alpha P64 as well as by human antisera. Western blotting of leptospiral serovars and 18 other bacterial species with R alpha P64 showed that P64 was cross-reactive with an equivalent antigen in a wide range of bacteria, indicating that it belongs to a family of antigens previously designated 'common antigen'. This putative common antigen from Leptospira appears to have a sub-surface location, but its function is not yet known.

Antigens recognized by the human immune response to vaccination with a bivalent hardjo/pomona leptospiral vaccine

Serum from volunteer subjects vaccinated with a bivalent whole cell vaccine of Leptospira interrogans serovar hardjo/serovar pomona grown in protein-free medium, was tested by the microscopic agglutination test (MAT), enzyme-immunoassay (EIA) and immunoblotting. Specific IgM antibodies to either serovars hardjo or pomona were detected in some subjects as early as 6 days after vaccination with peak antibody levels occurring 13-68 days after vaccination. Whereas all subjects produced specific IgM to both serovars, not all produced specific IgG to both serovars. Immunoblotting with hardjo sonicate revealed that all subjects produced IgM antibodies reacting with the 15, 23 and 28 kDa components of hardjo lipopolysaccharide (LPS), and most produced IgM antibodies that reacted with the 34.5 kDa flagellar doublet. In contrast, not all sera immunoblotted against pomona sonicate reacted with the 29 and 35 kDa components of pomona LPS. However all subjects produced antibodies reacting with a diffuse 14.4-27 kDa band. These antibodies appeared early in the immune response. Serum from the one vaccinated subject tested protected hamsters from acute lethal infection with serovar pomona.