Improved beam propagation method equations

Improved beam propagation method (BPM) equations are derived for the general case of arbitrary refractive-index spatial distributions. It is shown that in the paraxial approximation the discrete equations admit an analytical solution for the propagation of a paraxial spherical wave, which converges to the analytical solution of the paraxial Helmholtz equation. The generalized Kirchhoff-Fresnel diffraction integral between the object and the image planes can be derived, with its coefficients expressed in terms of the standard ABCD matrix. This result allows the substitution, in the case of an unaberrated system, of the many numerical steps with a single analytical step. We compared the predictions of the standard and improved BPM equations by considering the cases of a Maxwell fish-eye and of a Luneburg lens.

The joint of Tn916 circular intermediates is a homoduplex in Enterococcus faecalis

Tn916 is a 18-kb conjugative transposon originally identified in Enterococcus faecalis. The first step for Tn916 movement is its excision from the donor replicon with the formation of a nonreplicating covalently closed circular intermediate. Studies on formation of circular intermediates in Escherichia coli have shown that the joint between the Tn916 termini is a 6-bp heteroduplex formed by the two regions flanking the transposon before its excision (coupling sequences). In this work we studied the joint of Tn916 termini in circular intermediates formed in both E. coli and E. faecalis. Our strategy was to use direct sequencing of amplification products obtained from the joint region of single target molecules. In E. coli, 50% of circular intermediates contained a heteroduplex joint, while the remaining 50% displayed a homoduplex joint formed by one of the two coupling sequences. In E. faecalis, we could not demonstrate the presence of any heteroduplex joint. In this case 77.7% of the analyzed joints were formed by the left coupling sequence.

Angiocardiographic digital still images compressed via irreversible methods: concepts and experiments

We defined, implemented and tested two new methods for irreversible compression of angiocardiographic still images: brightness error limitation (BEL) and pseudo-gradient adaptive brightness and contrast error limitation (PABCEL). The scan path used to compress the digital images is based on the Peano-Hilbert plane-filling curve. The compression methods limit, for each pixel, the brightness errors introduced when approximating the original image (i.e. the difference between the values of corresponding pixels as grey levels). Additional limitations are imposed to the contrast error observed when considering along the scan path consecutive pixels of both the original and the reconstructed image. After previous testing on angiocardiographic images selected as clinically significant from 35 mm films, we enlarged our experiment to a set of 38 coronary angiograms digitally acquired. BEL and PABCEL methods were experimented according to several values of the implied thresholds. Up to a compression ratio of 9:1 for the BEL method and 10:1 for the PABCEL method, no deterioration of the reconstructed images were detected by human observers. After a visual evaluation, we performed a quantitative evaluation. The visualization of pseudo-colour difference images showed the capability of BEL and PABCEL for preserving the most significant clinical details of the original images. For comparison, we applied the JPEG (joint photographic experts group) image-compression standard to the same set of images. In this case, pseudo-colour difference images showed a homogeneous distribution of errors on the image surface. Quantitative compression results obtained by testing the different methods are comparable, but, unlike JPEG, BEL and PABCEL methods allow the user to keep under his direct control the maximum error allowed at each single pixel of the original image. These different behaviors are confirmed by the values obtained for the considered numerical quality quantifiers.

Commensal bacteria as vectors for mucosal vaccines against sexually transmitted diseases: vaginal colonization with recombinant streptococci induces local and systemic antibodies in mice

There is a need to develop vaccines to control the spread of sexually transmitted diseases (STDs). Novel immunization strategies that elicit a mucosal immune response in the genital tract, may show improved protection by preventing or at least limiting entry of the pathogenic micro-organism. However, it has proven difficult to obtain a local immune response in the vaginal mucosa. Our approach is based on the use of recombinant bacteria capable of colonizing mucosal surfaces as live vaccine vectors. The human commensal Streptococcus gordonii, engineered to express the E7 protein of human papillomavirus type 16, was used for intravaginal immunization of mice. A single inoculum of recombinant bacteria was sufficient to establish colonization of the murine vagina and therefore induce papillomavirus-specific vaginal IgA and serum IgG. Evidence that mucosal colonization with recombinant commensal bacteria can induce a local immune response in the female genital tract represents a significant step toward the development of new vaccines against STDs.

Comorbidity of drug dependence and other mental disorders: a two-phase study of prevalence at outpatient treatment centres in Italy

A cross-sectional multicentre study aimed at evaluating the prevalence of DSM III-R Axis I morbidity among drug addicts seeking treatment. Consecutive outpatients of the National Health Service's treatment units (aged 18-60 years, fulfilling criteria for drug dependence and without primary diagnosis of alcohol dependence) were enrolled at intake. In the first phase of the study, professional staff members evaluated current psychiatric morbidity of 317 clients clinically. In the second phase, trained interviewers administered the Composite International Diagnostic Interview and a European adaptation of the Addiction Severity Index to 65 probands. Some current psychiatric morbidity was found in 26.2% of subjects recruited during the first phase and in 22.2% during the second; lifetime comorbidity was ascertained in 32.3% of probands recruited in the second phase. Unfortunately, remarkable rates of undetermined diagnostic assessment during the second phase are due to refusers. The distribution of categorical diagnoses is somewhat different between the two samples, but the most frequent are Anxiety and Mood disorders in both. Primary versus secondary psychiatric diagnoses were also distinguished when evaluated over a lifetime. The rates of psychiatric comorbidity are low in this study as compared with previous investigations, but suffer from a poor compliance with structured diagnostic procedures by unselected probands. Other methodological factors may also affect this kind of research. Prospective studies are needed to evaluate the validity of comorbid diagnostic constructs and their prognostic significance. Also a concurrent assessment of Axis II disorders may be helpful to explain symptomatic polymorphism in case of multiple Axis I comorbidity.

Gram-positive commensal bacteria for mucosal vaccine delivery

To avoid the use of engineered pathogens for vaccine delivery, systems have been developed that allow the expression of heterologous antigens in commensal Gram-positive bacteria. In some cases, both a serum IgG and secretory IgA response are induced to the recombinant protein after vaccination, verifying the validity of the approach. These live recombinant bacteria may be used in the future to introduce a protective immune response to pathogenic microorganisms after mucosal colonization.

Conjugative transposon Tn916: evidence for excision with formation of 5'-protruding termini

Conjugative transposons are genetic elements able to promote their own intracellular transposition and intercellular conjugal transfer. They move by an excision-integration system related to that of lambdoid phages, in which the first step is the excision of the transposon from the donor replicon to form a covalently closed circular intermediate which contains a heteroduplex joint. In this work, sequencing both strands of the circular intermediate heteroduplex joint, it was found that, as during lambda phage excision, Tn916 excises from the host DNA by 5'-protruding staggered endonucleolytic cleavages.

Competence for genetic transformation in encapsulated strains of Streptococcus pneumoniae: two allelic variants of the peptide pheromone

The nucleotide sequence of comC, the gene encoding the 17-residue competence-stimulating peptide (CSP) of Streptococcus pneumoniae (L. S. Havarstein, G. Coomaraswamy, and D. A. Morrison, Proc. Natl. Acad. Sci. USA 92:11140-11144, 1995) was determined with 42 encapsulated strains of different serotypes. A new allele, comC2, was found in 13 strains, including the type 3 Avery strain, A66, while all others carried a gene (now termed comC1) identical to that originally described for strain Rx1. The predicted mature product of comC2 is also a heptadecapeptide but differs from that of comC1 at eight residues. Both CSP-1 and CSP-2 synthetic peptides were used to induce competence in the 42 strains; 48% of the strains became competent after the addition of the synthetic peptide, whereas none were transformable without the added peptides.

Effects of fluoxetine at antidepressant doses on short-term outcome of detoxified alcoholics

Compulsivity in alcohol-dependent patients is a frequent cause of early relapse in the post-detoxification period. The present study is a 2-month trial on detoxified alcoholics undergoing a double-blind placebo-controlled treatment with fluoxetine (20 mg/day). The rating instruments were the Hamilton Depression and Anxiety Scales, a visual analogue scale for alcohol craving and an original scale for evaluating alcohol withdrawal. The abstinence rate for fluoxetine-treated patients was significantly higher than in the placebo group, whereas no difference between treatments was found on the rating scales. Medical problems, additional psychiatric diagnoses, and family alcoholism were negatively correlated with abstinence. Two subgroups of patients having significantly different characteristics were identified as to the outcome, by means of cluster analysis. They are likely to represent two different stages in the evolution of alcoholism. Our results show that, independently from craving, fluoxetine at antidepressant doses is able to prevent relapses in weaned alcoholics. The anticompulsive therapy can positively influence the short-term outcome, while other factors are negatively associated with abstinence.

The tetracycline resistance gene tet(M) exhibits mosaic structure

Tetracycline resistance genes of the M class, tet(M), are typically found on mobile genetic elements as the conjugative transposons of gram-positive bacteria. By comparing the sequences of eight different tet(M) genes (from Enterococcus faecalis, Streptococcus pneumoniae, Staphylococcus aureus, Ureaplasma urealyticum, and Neisseria), a mosaic structure was detected which could be traced to two distinct alleles. The two alleles displayed a divergence of 8% and a different G/C content. The block structure of these genes provides evidence for the contribution of homologous recombination to the evolution and the heterogeneity of the tet(M) locus. Unlike described cases of chromosomally located mosaic loci, tet(M) is a relatively recently acquired determinant in the species examined and it would appear that mosaic structure within tet(M) has evolved after acquisition of the gene by the mobile genetic elements upon which it is located.

Exercise-induced hypoxaemia in emphysematous type chronic obstructive pulmonary disease

To investigate gas exchange response to exercise, we studied 16 male patients with moderate-to-serve airflow obstruction (forced expiratory volume in one second (FEV1) 39 +/- 10% of predicted value), mild-modest arterial hypoxaemia (arterial oxygen tension (Pa,O2) 9.6 +/- 0.87 kPa) and no arterial hypercapnia (arterial carbon dioxide tension (Pa,CO2) 5.04 +/- 0.45 kPa), referred to as emphysematous-type chronic obstructive pulmonary disease (COPD) clinical pattern. During maximal exercise tests, Pa,O2 increased by more than 0.3 kPa in eight patients (Group A) and fell by more than 0.3 kPa in the other eight patients (Group B). Pulmonary function tests, maximal inspiratory pressure at the mouth, values at maximum cycle incremental exercise and baseline arterial blood gases did not differ significantly between the two groups. We, therefore, showed that common pulmonary function measurements at rest and during exercise were not useful in identifying patients who underwent exercise-induced hypoxaemia. Furthermore, we suggest that patients with the same clinical pattern of chronic obstructive pulmonary disease and the same degree of airflow obstruction and gas exchange impairment could develop a different adaptation to a maximal exercise test, and that the presence of exercise-induced hypoxaemia might be related to pathological features of emphysema more than to different respiratory functional measurements.

A host-vector system for heterologous gene expression in Streptococcus gordonii

We have developed a host-vector system for heterologous expression in Streptococcus gordonii (Sg) Challis (formerly Streptococcus sanguis), a commensal bacterium of the human oral cavity. The system is based on (i) integration of plasmid insertion vectors into the chromosome of specially engineered recipient hosts, and (ii) the use of the M6-protein-encoding gene (emm6) as a partner for construction of translational gene fusions. M6 is a streptococcal surface protein already proven useful as a fusion partner for the delivery of foreign antigens to the surface of Sg [Pozzi et al., Infect. Immun. 60 (1992) 1902-1907]. Insertion vectors carry a drug-resistance marker, different portions of emm6 and a multiple cloning site to allow construction of a variety of emm6-based fusions. Upon transformation of a recipient host with an insertion vector, 100% of transformants acquire both the drug-resistance marker and the capacity of displaying the M6 molecule on the cell surface. Chromosomal integration occurred at high frequency in recipient host GP1221. Transformation with 1 microgram of insertion vector DNA yielded 8.1 X 10(5) transformants per ml of competent cells.

Characterization of conjugative transposon Tn5251 of Streptococcus pneumoniae

Tn5251 belongs to the Tn916-Tn1545 family of conjugative transposons (CT) and was found integrated into CT Tn5252, to form the composite element Tn5253 of Streptococcus pneumoniae. We show that Tn5251 is identical in structure and size to Tn916. DNA sequence analysis of a 4,419-bp segment containing the tet(M) gene showed that only 73 nucleotides out of 4,419 were different in the two CT. Essentially all differences (66/73) were clustered in a 688-bp segment of tet(M), which was 90% identical to Tn916 and 100% identical to the tet(M) genes of Tn1545 from S. pneumoniae and pOZ101 from Neisseria gonorrhoeae. DNA sequence analysis of the Tn5251/Tn5252 junction fragments allowed us (i) to determine Tn5251 termini, (ii) to define the 6-bp coupling sequences flanking the CT, and (iii) to infer the structure of the integration site (attB) of Tn5251 into Tn5252. Conjugal transfer of Tn5251 independent from Tn5253 could not be detected, even if we could show excision and formation of Tn5251 circular intermediates at a level of 5.4 copies per 10(6) chromosomes.

Managing different time granularities of clinical information by an interval-based temporal data model

In the field of databases, time management at different levels of granularity has been an issue for several years, for instance when dealing with clinical information from different databases using different time units, dealing with natural language expressions, or when dealing with temporal uncertainty. A temporal data model is proposed to manage the temporal aspect of data, presented at various and mixed levels of granularity. The concept of temporal assertions shapes the entire temporal information. The model provides a temporal dimension to the data by using intervals that can be specified at different granularities. The model supports a three-valued logic, where True, False and Undefined are the truth values. The temporal data model allows to manage some degrees of uncertainty when establishing temporal relationships between intervals or between temporal assertions, expressed at different granularities. The logical connectives and quantifiers can manage each of the three truth-values. We applied the temporal data model by implementing an object-oriented database system for managing follow-up clinical data from patients who underwent percutaneous transluminal coronary angioplasty.

Identification of Mycobacterium tuberculosis complex, Mycobacterium avium and Mycobacterium intracellulare by selective nested polymerase chain reaction

A nested polymerase chain reaction (PCR) procedure was devised for identification of mycobacteria. The outer reaction exploiting genus-specific sequences on the 16S rRNA gene was able to amplify specifically strains of the genus Mycobacterium. The identification of Mycobacterium tuberculosis complex, Mycobacterium avium and Mycobacterium intracellulare was accomplished by selective reamplification of the outer PCR product in three distinct inner amplifications exploiting species-specific primers mapping to a hypervariable region of mycobacterial 16S rRNA. Detection of mycobacteria, other than those for which species-specific primers were used, was accomplished by adding a supplementary genus-specific upper primer to one of the inner reactions. Specificity of amplification was confirmed for clinical isolates and reference strains of different mycobacterial species with the exception of a M. intracellulare type 7 strain which was recognized as M. avium. The amplification protocol presented thus provides a reliable and cost-effective way for identification of clinically relevant mycobacteria.

[Mental disorders of drug addicts in treatment: a study of prevalence with retrospective evaluation by means of structured diagnostic interviews]

The aim of this research is to evaluate current and lifetime psychiatric morbidity according to ICD-10 criteria of subjects in treatment for psychoactive substance dependence. It is a cross-sectional clinical-epidemiological study also collecting retrospective information by means of structured diagnostic interviews. Ninety-nine outpatients fulfilling criteria of eligibility were recruited by systematic sampling at 8 Italian National Health Service's Drug Dependence Units. Criteria of inclusion were the presence of clinical diagnosis of psychoactive substance dependence according to ICD-10 and age 18-45, while criteria of exclusion were pharmacological distress related to acute withdrawal from street drugs and the presence of severe cognitive impairment, delirium or acute psychoses in order to assure reliability of the interviews. Only 75 patients accepted to participate, were enrolled in the study and interviewed by means of a European adaptation of the Addiction Severity Index. Finally, the Composite International Diagnostic Interview was completed in 65 cases. The prevalence of current psychiatric morbidity for any disorder in addition to substance use disorders was 22.2%, and lifetime prevalence was 35.4% (but, if drop-out cases are excluded from calculation, the prevalence rates grow up to 30-35% and 50-55% respectively). Psychiatric morbidity is more frequent among females and is unrelated to age or lifetime duration of substance use. In almost one-half of the cases mental disorders arose before the beginning of substance use. By order of frequence, anxiety, affective, and schizophrenic syndromes are the most common comorbid diagnoses. Affective disorders are more often secondary, since they mostly develop after the beginning of psychotropic substance use and are uncommon among currently abstinent subjects. Finally, outpatients affected by psychotic disorders are not likely to abstain from psychotropic drugs during the treatment. Psychiatric comorbidity is a considerable point in the clinical management of drug dependence, and for primary and secondary prevention of substance use disorders.

Mucosal and systemic immune responses to a recombinant protein expressed on the surface of the oral commensal bacterium Streptococcus gordonii after oral colonization

To circumvent the need to engineer pathogenic microorganisms as live vaccine-delivery vehicles, a system was developed which allowed for the stable expression of a wide range of protein antigens on the surface of Gram-positive commensal bacteria. The human oral commensal Streptococcus gordonii was engineered to surface express a 204-amino acid allergen from hornet venom (Ag5.2) as a fusion with the anchor region of the M6 protein of Streptococcus pyogenes. The immunogenicity of the M6-Ag5.2 fusion protein was assessed in mice inoculated orally and intranasally with a single dose of recombinant bacteria, resulting in the colonization of the oral/pharyngeal mucosa for 10-11 weeks. A significant increase of Ag5.2-specific IgA with relation to the total IgA was detected in saliva and lung lavages when compared with mice colonized with wild-type S. gordonii. A systemic IgG response to Ag5.2 was also induced after oral colonization. Thus, recombinant Gram-positive commensal bacteria may be a safe and effective way of inducing a local and systemic immune response.

Dosage of Tn916 circular intermediates in Enterococcus faecalis

Upon excision, conjugative transposon Tn916 forms a nonreplicating circular intermediate (CI), which is essential both for transposition and conjugal transfer. In this work we developed an assay to quantify the circular forms of Tn916. By this method we defined a new measurable trait of Tn916-carrying strains: the "CI copy number." CI dosage was performed by nested PCR (with primers designed on Tn916 termini) in a limiting dilution assay, where Poisson statistics were used to calculate the number of PCR amplification targets from the proportion of the negative endpoints. The number of CI was normalized to the number of bacterial chromosomes. This method enabled us to study the relationship between CI copy number, presence of tetracycline (the resistance marker of Tn916) in the culture medium, and conjugation frequency. Three isogenic strains of Enterococcus faecalis OG1 with Tn916 inserted at different sites on the chromosome were investigated for CI content. CI copy number varied depending on the strain, ranging between 7.8 and 610 copies per 10(6) chromosomes. Growth in liquid media containing tetracycline provoked an important increase both in CI copy number and conjugation frequency. This effect was more marked in low-frequency donors. While cell-cell contact during filter mating did not produce an increase in CI copy number, Tn916 conjugation frequency was found to be dependent on CI copy number in donor cells. The dose-response curve showed a linear relationship with a slope of 0.74, for the entire range of conjugation frequencies tested (from 5.1 x 10(-8) to 2.8 x 10(-6) transconjugants per donor.

Immunization of mice by oral colonization with live recombinant commensal streptococci

To test the use of recombinant streptococci as live vaccine vectors, colonization/immunization experiments were performed with Streptococcus gordonii expressing heterologous cell-surface antigens. Three isogenic strains of S. gordonii were used: a wild-type, a recombinant expressing the M6 protein of Streptococcus pyogenes, and a recombinant expressing the E7 protein of human papillomavirus type 16 as a fusion with the M6 protein. A single dose of live bacteria was used to inoculate outbred mice, and it was found that: (i) mice were stably colonized by a single intranasal/oral inoculum of S. gordonii; (ii) recombinant strains were equally effective as wild-type in colonizing mice; (iii) two months after the inoculum, oral/pharyngeal swabs of 83.3% of animals were still positive for isolation of S. gordonii; (iv) recombinant S. gordonii isolated from colonized mice were always positive for expression of the heterologous antigens; (v) live bacteria induced a systemic immune response, since sera of mice colonized with recombinant S. gordonii contained IgG specific for the heterologous cell-surface antigens; (vi) this immune response depended upon the effective colonization by live bacteria, since killed bacteria did not induce such a response.