Modelling multi-site transmission of the human papillomavirus and its impact on vaccination effectiveness.

OBJECTIVE: Previous HPV models have only included genital transmission, when evidence suggests that transmission between several anatomical sites occurs. We compared model predictions of population-level HPV vaccination effectiveness against genital HPV16 infection in women, using a 1) uni-site (genital site), and a 2) multi-site model (genital and one extragenital site). METHODS: We developed a uni-site and a multi-site deterministic HPV transmission model, assuming natural immunity was either site-specific or systemic. Both models were calibrated to genital HPV16 prevalence (5%-7.5%), whilst the multi-site model was calibrated to HPV16 prevalence representative of oral (0%-1%) and anal (1%-7.5%) sites. For each model, we identified 2500 parameter sets that fit endemic genital and extragenital prevalences within pre-specified target ranges. In the Base-case analysis, vaccination was girls-only with 40% coverage. Vaccine efficacy was 100% for all sites with lifetime protection. The outcome was the relative reduction in genital HPV16 prevalence among women at post-vaccination equilibrium (RRprev). RRprev was stratified by extragenital prevalence pre-vaccination. RESULTS: Under assumptions of site-specific immunity, RRprev with the multi-site model was generally greater than with the uni-site model. Differences between the uni-site and multi-site models were greater when transmission from the extragenital site to the genital site was high. Under assumptions of systemic immunity, the multi-site and uni-site models yielded similar RRprev in the scenario without immunity after extragenital infection. In the scenario with systemic immunity after extragenital infection, the multi-site model yielded lower predictions of RRprev than the uni-site model. CONCLUSIONS: Modelling genital-site only transmission may overestimate vaccination impact if extragenital infections contribute to systemic natural immunity or underestimate vaccination impact if a high proportion of genital infections originate from extragenital infections. Under current understanding of heterosexual HPV transmission and immunity, a substantial bias from using uni-site models in predicting vaccination effectiveness against genital HPV infection is unlikely to occur.

Excitation with effective subcycle laser pulses.

We have used laser pulses with a temporally shaped polarization to demonstrate the multiphoton excitation of the xenon 5g state within a subcycle of a laser pulse. Our polarization gated laser pulses are composed of circularly polarized sections at the leading and trailing edges of the pulse and of an experimentally defined linearly polarized central part. Only the linear part (the gate) of the pulse can excite neutral xenon in the 5g state. The transition cannot be driven with circularly polarized light because the number of photons needed would cause a violation of selection rules for the change of the magnetic quantum number. We show that the linearly polarized central part can be reduced to a subcycle pulse. This allows us to study excitation with an effective pulse as short as 2.3 fs at 800 nm. Electron imaging spectroscopy has been used to visualize the presence of excited states as a function of the pulse duration of the gate.

Wavelength and intensity dependence of short pulse laser xenon double ionization between 500 and 2300 nm.

The wavelength and intensity dependence of xenon ionization with 50 fs laser pulses has been studied using time-of-flight mass spectrometry. We compare the ion yield distribution of singly and doubly charged xenon with the Perelomov-Popov-Terent'ev (PPT) theory, Perelomov, Popov, and Terent'ev, Zh. Eksp. Teor. Fiz. 50, 1393 (1966) [Sov. Phys. JETP 23, 924 (1966)], in the regime between 500 and 2300 nm. The intensity dependence for each wavelength is measured in a range between 1 x 10(13) and 1 x 10(15) W/cm2. The Xe+-ion signal is in good agreement with the PPT theory at all used wavelengths. In addition we demonstrate that ionic 5s5p6 2S state is excited by an electron impact excitation process and contributes to the nonsequential double ionization process.

Initial recovery of vision after early monocular deprivation in kittens is faster when both eyes are open.

A comparison was made of the speed of visual recovery in the deprived eye of kittens after a 6-day period of monocular deprivation imposed at 5-9 weeks of age in two postdeprivation conditions. In one condition, binocular recovery (BR), both eyes were open, whereas in the other condition, reverse lid-suture (RLS), the formerly nondeprived eye was closed to force the animal to use the originally deprived eye. In littermate pairs, BR kittens began to recover form vision 12 to 30 h before those subjected to RLS. The vision of the deprived eye of the BR animals remained superior to that of their RLS littermates for 4-8 days. Although this finding is difficult to reconcile with competitive mechanisms of synaptic plasticity, it supports a prediction of an alternative model of synaptic plasticity [Bienenstock, E. L., Cooper, L. N. & Munro, P. W. (1982) J. Neurosci. 2, 32-48] for slower initial recovery with RLS because of the time required to reset the modification threshold.

Evaluation of the health risk associated with exposure to chloroform in indoor swimming pools.

The exposure of swimmers to chloroform (CHCl3) was investigated in indoor swimming pools of the Quebec City region along with the associated carcinogenic risk. Six training sessions involving 52 competition swimmers (11 to 20 yr old) were conducted in 3 different pools, while 12 adult leisure swimmers attended 5 sessions, each held in a different pool. For each session, water and ambient air CHCl3 concentrations were measured and CHCl3 levels in alveolar air samples (CHCl3 ALV) collected from swimmers prior to entering the swimming pool premises and after 15, 35, and 60 min of swimming. Mean water concentrations varied from 18 microg/L to 80 microg/L, while those in air ranged from 78 microg/m3 to 329 microg/m3. Multiple linear regression analyses revealed that CHCl3 ALV values in competition swimmers were strongly correlated to ambient air and water levels, and to a lesser degree to the intensity of training. Only ambient air concentration was positively correlated to CHCl3 ALV in the leisure group. Concentrations of CHCl3 metabolites bound to hepatic and renal macromolecules, estimated using a physiologically based pharmacokinetic (PBPK) model, were 1.6 and 1.9 times higher for the competition swimmers than for the leisure swimmers, respectively. The highest hepatic concentration predicted in competition swimmers, 0.22 microg CHCl3 equivalents/kg of tissue, was at least 10,000 times lower than the smallest no observed effect level for liver tumors in animals. Data indicate that the safety margin is therefore very large, for competitive swimmers as well as for leisure swimmers.

Identification and characterization of the gene for a novel C-type lectin (CLECSF7) that maps near the natural killer gene complex on human chromosome 12.

We report the identification and characterization of a novel C-type lectin gene, named HECL (HGMW-approved symbol CLECSF7), that maps close to the natural killer gene complex on human chromosome 12p13. Sequence analysis revealed a complete open reading frame of 549 bp comprising several putative glycosylation and phosphorylation sites as well as a C-terminal C-type carbohydrate-recognition domain. Homology analysis revealed that HECL exhibits a significant degree of divergence from the natural killer cell receptors that comprise the natural killer gene complex. These natural killer cell receptors all belong to group V of the C-type lectin superfamily. HECL, however, is most closely related to the sole group II C-type lectins reported to map near this region of the genome, the murine Nkcl and Mpcl genes. Like Nkcl, HECL is expressed in a variety of hematopoietic cell types and has a complete Ca(2+)-binding site 2. Despite the presence of critical amino acids for sugar binding in Ca(2+)-binding site 2, HECL does not seem to bind carbohydrate. Moreover, HECL is the first non-receptor-like C-type lectin to map near the natural killer gene complex.

Surgically created neural pathways mediate visual pattern discrimination.

Combined lesions of retinal targets and ascending auditory pathways can induce, in developing animals, permanent retinal projections to auditory thalamic nuclei and to visual thalamic nuclei that normally receive little direct retinal input. Neurons in the auditory cortex of such animals have visual response properties that resemble those of neurons in the primary visual cortex of normal animals. Therefore, we investigated the behavioral function of the surgically induced retino-thalamo-cortical pathways. We showed that both surgically induced pathways can mediate visually guided behaviors whose normal substrate, the pathway from the retina to the primary visual cortex via the primary thalamic visual nucleus, is missing.

Visual recovery after monocular deprivation is driven by absolute, rather than relative, visually evoked activity levels.

It is now well established that the anatomical and functional development of the central visual pathways of a number of higher mammalian species is activity-dependent [1-3]. This dependence was revealed by the functional effects of an early period of monocular deprivation, where one eye of a young animal was deprived for a time of patterned visual input. Subsequently, most cells in the visual cortex (area 17) could be excited only by visual stimuli delivered to the non deprived eye [4-6] and the animal appeared blind through the deprived eye [7,8]. These effects have been attributed to a competitive activity-dependent mechanism in development, whereby the two eyes compete for control of cortical cells [9,10]. There are, however, suggestions that the substantial recovery that can occur after monocular deprivation may be mediated by a different mechanism. Here, insight into the nature of this mechanism has been provided by monitoring the speed of changes in the vision of the deprived eye of a kitten after 6 days of monocular deprivation. Although both eyes were open during the recovery period, the kitten was able to see with its deprived eye only 2 hours after visual input was restored to this eye. The visual acuity of this eye improved rapidly in the first 24 hours and continued in an orderly way for 6 weeks. In contrast to the effects during monocular deprivation, which depend upon a competitive activity-dependent process, we propose that the events that follow deprivation rely on a mechanism driven by the absolute level of visually evoked activity through the formerly deprived eye.

Box Handling in the Loading and Unloading of Vans.

The handling of 2,306 boxes being loaded or unloaded from vans onto or from 4-wheeled trolleys by 31 handlers in a warehouse were characterized. Handling was videotaped and characterized through an analysis grid completed by three trained observers. The following execution parameters were observed: nature of the exertion applied by the upper limbs, plane and direction of the exertion, resulting displacement of the box, grip, use of the lower limbs and the back. Results show that execution parameters used by handlers vary considerably from those usually recommended or studied. For example, symmetric grips were rarely used (4%). The grip was modified during the handling of half the boxes. Significant knee flexion was rarely observed (3% of exertions). Each box was moved by applying an average of 3.5 different exertions. Exertions were mostly applied in a plane parallel to the shoulders; they were rarely executed in a strict sagittal plane (11%). The implication of these observations are discussed.

Origin of optical activity in the purple bacterial photoreaction center.

The photoreaction center (RC) of purple bacteria contains four bacteriochlorophyll (Bch) and two bacteriopheophytin (Bph) molecules as prosthetic groups. Their optical activity, as measured by circular dichroism (CD) spectroscopy, is largely increased in situ as compared to organic solutions. The all-exciton hypothesis posits that this enhanced optical activity is entirely due to excitonic interactions between the electronic transitions of all six bacteriochlorin molecules. Using the simple exciton theory, this model predicts that the near-infrared CD spectra should be conservative. The fact that they are not, whether the special pair of Bch (SP) that constitutes the primary electron donor is reduced or oxidized, has been explained by hyperchromic effects. The present work tests this hypothesis by successively eliminating the absorption and, therefore, the optical activity of the Bphs and of the non-special-pair (non-SP) Bchs. This was accomplished by trapping these pigments in their reduced state. RC preparations with the four non-SP bacteriochlorins trapped in their reduced state and, therefore, with an intact SP displayed conservative CD spectra. RC preparations with only the electronic transitions of SP and of one non-SP Bch also showed conservative CD spectra. These conservative CD spectra and their corresponding absorption spectra were simulated using simple exciton theory without assuming hyperchromic effects. Bleaching half of the 755-nm absorption band by phototrapping one of the two Bph molecules led to the complete disappearnce of the corresponding CD band. This cannot be explained by the all-exciton hypothesis. These results suggest that the optical activity of the SP alone, or with one non-SP Bch, is due to excitonic interactions.(ABSTRACT TRUNCATED AT 250 WORDS)

A pastoral approach to psychiatric care.

Rev. Gérard Gingras is the chaplain and Lise Savoy-Malenfant, a pastoral care worker at the Centre hospitalier Robert-Giffard in Beauport, Quebec. They provide some insight into the unique techniques needed to minister to those who have a psychiatric illness.

Phototrapping of doubly reduced monomeric bacteriochlorophyll in the photoreaction center of Ectothiorhodospira sp.

The photoreaction center from the purple sulfur bacterium Ectothiorhodospira sp. was illuminated in the presence of reduced cytochrome c or dithionite under anaerobic conditions. This treatment first caused the monoelectronic reduction of both molecules of bacteriopheophytin (Bph), phi A and phi B, as witnessed by the appearance of EPR and optical signals typical of singly-reduced bacteriochlorins. Continued illumination under the same reducing conditions caused both of these signals to disappear. Such disappearance was accompanied by a complete bleaching of the Qx and Qy absorption bands of Bph but not of the corresponding transitions of bacteriochlorophyll (Bchl). These phenomena are interpreted by a double reduction of phi A and phi B. As long as the medium remained reducing and anaerobic, these changes were stable. Prolonged illumination under the same reducing conditions finally led to the bleaching of the Qx (600 nm) and Qy (800 nm) bands of Bchl but not of the 880-nm band. This generated no EPR or 645-nm absorption signals due to singly-reduced Bchl. The bleaching kinetics of the 800-nm band was biphasic and paralleled a shift of the peak wavelength. This is interpreted by a double reduction of both molecules of monomeric Bchl BA and BB in an undetermined order. After bleaching of the 800-nm band has reached saturation, the absorbance ratio of the 800/880-nm absorption bands remains constant, as would be expected if the ultimate spectrum was that of the primary electron donor. These experiments demonstrate the photoreduction of Bchl and allow the absorption spectrum of the primary donor to be measured for the first time.(ABSTRACT TRUNCATED AT 250 WORDS)

The puh structural gene coding for the H subunit of the Rhodospirillum rubrum photoreaction center.

The Rhodospirillum rubrum structural gene puh, coding for the photoreaction center H polypeptide, and three other putative genes that surround puh were cloned and sequenced. The deduced 257 amino acid H polypeptide has a molecular weight of 27,909, in close agreement with polyacrylamide gel electrophoresis determination. Hydropathy plots predict a single hydrophobic alpha helix. The H polypeptide of Rhodospirillum rubrum shares only 23% of its residues with all three of the H polypeptides from Rhodopseudomonas viridis, Rhodobacter capsulatus, and Rhodobacter sphaeroides. Despite this apparent low degree of similarity, statistical analysis leaves no doubt about their close relatedness. Interspecies evolutionary distance, assessed by this analysis, confirms the closeness of the two Rhodobacter species, Rhodospirillum rubrum and Rhodopseudomonas viridis being approximately equidistant from them. Three regions of the H polypeptide are highly conserved in all four species. They correspond to known contact points of H with the complex of the other two (L and M) subunits on the cytoplasmic side of the membrane. A glutamic acid residue (H polypeptide residue 177), conserved in the other bacteria and suggested to be involved in the binding of secondary quinone QB, is replaced by serine in Rhodospirillum rubrum. The open reading frames G115, I2372, and I3087 are predicted to, respectively, encode polypeptides of 480, 224, and 155 residues coiled in 10, 2, and 1 transmembrane helices. Open reading frame G115 shares 56% identical residues with F1696, a sequence arranged in the genome of Rhodobacter capsulatus. The gene product of ORF I3087 is predicted to share highly similar sequences with nitrogenase reductase (encoded by nifH) of 11 different bacterial species and is suggested to have a regulatory function.

Supramolecular arrangement of Rhodospirillum rubrum B880 holochrome as studied by radiation inactivation and electron paramagnetic resonance.

Oxidation of the B880 antenna holochrome gives rise to a 3.8-G linewidth electron paramagnetic resonance (EPR) signal that is considerably narrower than the 13-G signal of monomeric bacteriochlorophyll (Bchl) cation. Radiation inactivation was used to verify a model according to which this linewidth narrowing is due to delocalization over several Bchl molecules. Chromatophores of the photoreaction centerless mutant F24 of Rhodospirillum rubrum were subjected to different doses of gamma-radiation. This induced not only a decay of the EPR signal amplitude but also its linewidth broadening. According to target theory, the induced amplitude decay of the EPR signal had a target size of 10.5 kDa. This is attributed to an elementary structure (alpha1beta1Bchl2), whose number in the membrane would limit the rate of encounter with ferricyanide and thus the formation of unpaired spins. We applied Bernoulli statistics to predict, for a given survival probability of the signal, the number of surviving elementary structures in aggregates of (alpha1beta1Bchl2)n where n was varied from 4 to 7. Using an equation that predicted the Bchl special pair in the photo-reaction center, we were able to simulate the observed relationship between the EPR linewidth and the dose of radiation. The best fit was obtained with a hexameric structure alpha1beta1Bchl2)6.

Plasmid from photosynthetic bacterium Ectothiorhodospira Sp. carries a transposable streptomycin resistance gene.

Centrifugation through a cesium chloride density gradient and agarose gel electrophoresis of the DNA from the purple non-sulfur photosynthetic bacterium Ectothiorhodospira sp. resolved a single extrachromosomal element, plasmid pDG1. Its size was estimated to be 13.2 kilobases by restriction endonuclease mapping. Plasmid pDG1 and two restriction fragments thereof were cloned in Escherichia coli C600 with plasmid pBR327 as a vector to form mixed plasmids pDGBR1, pDGBR2, and pDGBR3. The resistance to streptomycin and mercury found in Ectothiorhodospira sp. was transferred to E. coli C600 after transformation with pDGBR1 but not with pDGBR2 and pDGBR3. The replication origin of pDG1 was estimated to be within a 2-kilobase restriction fragment of pDG1 by monitoring its replication in E. coli HB101, using a kanamycin resistance reporter gene. High stringency molecular hybridization with 32P-labeled pDG1 identified specific fragments of genomic DNA, suggesting the integration of some plasmid sequences. In accordance with the hypothesis that this integration is due to a transposon, we tested the transfer of streptomycin resistance from pDG1 into plasmid pVK100 used as a target. For this test, we regrouped in the same cells of E. coli HB101, pDGBR1 and mobilizable plasmid pVK100 (tetr,kmr). We used the conjugation capacity of the pVK100/pRK2013 system to rescue the target plasmid pVK100 into nalidixic acid-resistant E. coli DH1. The transfer frequency of streptomycin resistance into pVK100 was 10(-5), compatible with a transposition event. In line with the existence of a transposon on pDG1, heteroduplex mapping indicated the presence of inverted repeats approximately 7.5 kb from one another.

Mapping of the puh messenger RNAs from Rhodospirillum rubrum. Evidence for tandem promoters.

The mRNA transcripts of Rhodospirillum rubrum gene puh, coding for the H subunit of the photoreaction center, and of genes flanking puh were analyzed by blot hybridization. Open reading frame G115, upstream of structural gene puh, is transcribed as a 2.25-kilobase mRNA. Gene puh itself is transcribed as two mRNAs of 1118 and 1032 nucleotides. Mung bean nuclease protection analysis shows that the puh transcripts have different 5' termini within open reading frame G115 and a unique rho-independent termination signal within open reading frame I2372. The lifetimes of the puh messages, as determined by an oxygen blockade of transcription, were 10 and 12 min for the large and small puh mRNAs, respectively. An expression vector carrying a chloramphenicol acetyltransferase gene was used to select promoters in DNA stretches upstream of the startpoints of each of these transcripts. Chloramphenicol resistance was expressed in Escherichia coli, using as a promoter a 179-nucleotide stretch upstream of the small mRNA startpoint but not from a 124-nucleotide stretch upstream of the large mRNA startpoint. The promoter for the small mRNA, designated Ppuh2, is thought to encompass in its -10 and -35 regions a sigma 70-like RNA polymerase recognition sequence. The region upstream of the large message startpoint contains a sequence similar in its -12 and -24 regions to promoter sequences recognized by the sigma 60 RNA polymerase holoenzyme. This is designated as promoter Ppuh1.Ppuh1 is proposed to be strictly regulated by light intensity and by oxygen tension while Ppuh2 would be less sensitive to these parameters.

The structural genes coding for the L and M subunits of Rhodospirillum rubrum photoreaction center.

In Rhodospirillum rubrum, pufL, and pufM, the structural genes coding for the photoreaction center L and M polypeptides, are comprised respectively of 831 and 921 nucleotides. They are separated by a stretch of 12 nucleotides between the TAA stop codon of pufL and the first base of the ATG initiation codon of pufM. The predicted amino acid sequence of the L and M polypeptides, respectively, contain 275 and 305 residues with corresponding molecular weights of 30,473 and 33,978. Their sequences are highly homologous to those of Rhodobacter sphaeroides, Rhodobacter capsulatus, and Rhodopseudomonas viridis. As can be deduced from the crystallographic structure of other photoreaction centers, the regions of greatest similarity are the binding sites of the cofactors involved in the photochemical reaction rather than the protein secondary structure. L and M contain, at conserved positions of their sequences, three main clusters of positively charged residues on the cytoplasmic side of the membrane. This arrangement may be involved in protein orientation during membrane assembly. Evolutionary distance of pufL and pufM, as assessed by substitution frequency analysis, confirms the closeness of the two Rhodobacter species, the other two species being equidistant from one another. Interspecies evolutionary distance is greater for pufL than for pufM.

Structure and expression of the puf operon messenger RNA in rhodospirillum rubrum.

In Rhodospirillum rubrum, the genes coding for the alpha and beta polypeptides of the B880 antenna (pufA,B) and the L and M polypeptides of the photoreaction center (pufL,M) are clustered on operon puf. In oxygen-limited cells, the puf mRNA is present as species of 2561, 640, and 617 nucleotides. Aerated cells contain only traces of these mRNAs. The large mRNA encodes the alpha,beta, L, and M polypeptides, whereas the small mRNAs encode only alpha and beta. S1 nuclease protection mapping showed these transcripts to have a common 5' end, immediately downstream of a region of dyad symmetry and at 166 nucleotides upstream of the initiation codon of pufB. The 3' termini of the small transcripts are located in the intercistronic region between pufA and pufL, downstream of another region of dyad symmetry. This region is highly conserved in Rhodospirillum rubrum, Rhodobacter capsulatus, and Rhodobacter sphaeroides and shares 61% sequence similarity with the repetitive extragenic palindromic sequences of Escherichia coli. The slightly heterogeneous 3' termini of the large transcript are downstream of a region of dyad symmetry characteristic of rho-independent transcription termination. Following a shift from oxygen-limited to aerated conditions, the pufL,M and the pufA,B mRNAs decayed with respective half-lives of 9 and 20 min. These high relative stabilities, attributed to secondary structure, are in accord with the mole ratio (2:1) of the pufA,B/pufL,M messages. While the differential expression of alpha,beta/L,M congruent to 15 is thought to be due, in part, to this relative stability, the main factor may be a more efficient translation initiation for pufA,B than for pufL,M.

Effects of sucralfate on gastric prostaglandin and leukotriene synthesis: relationship to protective actions.

The mechanism of the protective actions of sucralfate against ethanol-induced gastric mucosal damage in the rat has been investigated. In particular, the role of prostaglandins as mediators of such protection was assessed. Oral administration of sucralfate at a dose causing a significant reduction of ethanol-induced gastric damage (500 mg/kg) did not significantly alter gastric 6-ketoprostaglandin F1 alpha synthesis. Pretreatment with indomethacin at a dose that inhibited gastric cyclooxygenase activity by an average of 88% did not affect the protective actions of sucralfate. To further investigate the mechanism of action of sucralfate, an ex vivo gastric chamber model was used in which sucralfate could be applied to only one side of the mucosa. Sucralfate did not affect gastric prostaglandin synthesis, but did cause a significant increase in leukotriene C4 synthesis, a fall in transmucosal potential difference, and a significant decrease in gastric myeloperoxidase activity on the side exposed to sucralfate. These observations suggest that sucralfate has an irritant action on the mucosa. The release of mediators in response to such irritation may play an important role in the protective action of sucralfate. The present study supports the hypothesis that prostaglandins do not mediate the protection afforded by exposure to sucralfate.