Investigation of a combination therapy approach for the treatment of melioidosis

The efficacy of finafloxacin as a component of a layered defense treatment regimen was determined in vitro and in vivo against an infection with Burkholderia pseudomallei. Doxycycline was down-selected from a panel of antibiotics evaluated in vitro and used in combination with finafloxacin in a Balb/c mouse model of inhalational melioidosis. When treatment was initiated at 24 h post-infection with B. pseudomallei, there were no differences in the level of protection offered by finafloxacin or doxycycline (as monotherapies) when compared to the combination therapy. There was evidence for improved bacterial control in the groups treated with finafloxacin (as monotherapies or in combination with doxycycline) when compared to mice treated with doxycycline. Survival comparisons of finafloxacin and doxycycline (as monotherapies) or in combination initiated at 36 h post-infection indicated that finafloxacin was superior to doxycycline. Doxycycline was also unable to control the levels of bacteria within tissues to the extent that doxycycline and finafloxacin used in combination or finafloxacin (as a sole therapy) could. In summary, finafloxacin is a promising therapy for use in the event of exposure to B. pseudomallei.

Finafloxacin, a Novel Fluoroquinolone, Reduces the Clinical Signs of Infection and Pathology in a Mouse Model of Q Fever

Finafloxacin is a novel fluoroquinolone with optimal antibacterial activity in low pH environments, therefore offering a therapeutic advantage over some traditional antibiotics, in treating bacterial infections associated with acidic foci. Coxiella burnetii, the causative agent of Q fever, is a bacterium which resides and replicates in acidic intracellular parasitic vacuoles. The efficacy of finafloxacin was evaluated in vivo using the A/J mouse model of inhalational Q fever and was compared to doxycycline, the standard treatment for this infection and ciprofloxacin, a comparator fluoroquinolone. Finafloxacin reduced the severity of the clinical signs of infection and weight loss associated with Q fever, but did not reduce the level of bacterial colonization in tissues compared to doxycycline or ciprofloxacin. However, histopathological analysis suggested that treatment with finafloxacin reduced tissue damage associated with C. burnetii infection. In addition, we report for the first time, the use of viable counts on axenic media to evaluate antibiotic efficacy in vivo.

The efficacy of HI-6 DMS in a sustained infusion against percutaneous VX poisoning in the guinea-pig

Post-exposure nerve agent treatment usually includes administration of an oxime, which acts to restore function of the enzyme acetylcholinesterase (AChE). For immediate treatment of military personnel, this is usually administered with an autoinjector device, or devices containing the oxime such as pralidoxime, atropine and diazepam. In addition to the autoinjector, it is likely that personnel exposed to nerve agents, particularly by the percutaneous route, will require further treatment at medical facilities. As such, there is a need to understand the relationship between dose rate, plasma concentration, reactivation of AChE activity and efficacy, to provide supporting evidence for oxime infusions in nerve agent poisoning. Here, it has been demonstrated that intravenous infusion of HI-6, in combination with atropine, is efficacious against a percutaneous VX challenge in the conscious male Dunkin-Hartley guinea-pig. Inclusion of HI-6, in addition to atropine in the treatment, improved survival when compared to atropine alone. Additionally, erythrocyte AChE activity following poisoning was found to be dose dependent, with an increased dose rate of HI-6 (0.48mg/kg/min) resulting in increased AChE activity. As far as we are aware, this is the first study to correlate the pharmacokinetic profile of HI-6 with both its pharmacodynamic action of reactivating nerve agent inhibited AChE and with its efficacy against a persistent nerve agent exposure challenge in the same conscious animal.

Inhaled Liposomal Ciprofloxacin Protects against a Lethal Infection in a Murine Model of Pneumonic Plague

Inhalation of Yersinia pestis can lead to pneumonic plague, which without treatment is inevitably fatal. Two novel formulations of liposome-encapsulated ciprofloxacin, ‘ciprofloxacin for inhalation’ (CFI, Lipoquin^®) and ‘dual release ciprofloxacin for inhalation’ (DRCFI, Pulmaquin^®) containing CFI and ciprofloxacin solution, are in development. These were evaluated as potential therapies for infection with Y. pestis. In a murine model of pneumonic plague, human-like doses of aerosolized CFI, aerosolized DRCFI or intraperitoneal (i.p.) ciprofloxacin were administered at 24 h (representing prophylaxis) or 42 h (representing treatment) post-challenge. All three therapies provided a high level of protection when administered 24 h post-challenge. A single dose of CFI, but not DRCFI, significantly improved survival compared to a single dose of ciprofloxacin. Furthermore, single doses of CFI and DRCFI reduced bacterial burden in lungs and spleens to below the detectable limit at 60 h post-challenge. When therapy was delayed until 42 h post-challenge, a single dose of CFI or DRCFI offered minimal protection. However, single doses of CFI or DRCFI were able to significantly reduce the bacterial burden in the spleen compared to empty liposomes. A three-day treatment regimen of ciprofloxacin, CFI, or DRCFI resulted in high levels of protection (90–100% survival). This study suggests that CFI and DRCFI may be useful therapies for Y. pestis infection, both as prophylaxis and for the treatment of plague.

SGO1 but not SGO2 is required for maintenance of centromere cohesion in Arabidopsis thaliana meiosis

Shugoshin is a protein conserved in eukaryotes and protects sister chromatid cohesion at centromeres in meiosis. In our study, we identified the homologs of SGO1 and SGO2 in Arabidopsis thaliana. We show that AtSGO1 is necessary for the maintenance of centromere cohesion in meiosis I since atsgo1 mutants display premature separation of sister chromatids starting from anaphase I. Furthermore, we show that the localization of the specific centromeric cohesin AtSYN1 is not affected in atsgo1, suggesting that SGO1 centromere cohesion maintenance is not mediated by protection of SYN1 from cleavage. Finally, we show that AtSGO2 is dispensable for both meiotic and mitotic cell progression in Arabidopsis.

In vitro and in vivo testing of novel ultrathin PCL and PCL/PLA blend films as peripheral nerve conduit

In an attempt to obviate the drawbacks of nerve autograft, ultrathin microporous biodegradable PCL and PCL/PLA films were tested for their compatibility with motor neuron-like NG108-15 cells and primary Schwann cells. Data obtained from MTS colorimetric and DNA fluorimetric assays showed that both cell lines readily attached and proliferated on these materials. Images taken using scanning electron microscope and fluorescence microscope confirmed these observations. Enhanced cell-surface interaction was achieved by pretreating the films in NaOH solution. Importantly, NG108-15 cells could be induced into differentiated phenotype with long, un-branched neurites growing across the surface of the materials. The bipolar spindle-shaped phenotype of Schwann cells was also retained on these scaffolds. Positive immunochemical staining using antibodies against neurofilament for NG108-15 cells and S100 for Schwann cells indicated the expression of these marker proteins. In a small-scaled pilot testing, the performance of PCL conduits in bridging up a 10 mm gap in rat sciatic nerve model was assessed. Immunohistochemical staining showed that regenerated nerve tissue and penetrated Schwann cells have the potential to span the whole length of the conduit in 2 weeks.

Telomere distribution and dynamics in somatic and meiotic nuclei of Arabidopsis thaliana

The ends of linear eukaryotic chromosomes are protected by the telomere, a specialised nucleoprotein complex. The primary role of the telomere is to protect the chromosome ends from being degraded or recognised and processed as double strand breaks. Additionally, the telomeres are involved in interphase chromosome organisation and also in chromosome pairing, synapsis and movement during meiotic prophase. The main emphasis of this review is concerned with the distribution and dynamics of the telomeres in the somatic cell and meiocytes of plants, focusing on the model plant Arabidopsis thaliana. In Arabidopsis the telomeres are organised around the nucleolus in both the somatic and meiotic interphase. One of the outstanding questions in meiosis is how homologous chromosomes pair (align) and synapse during meiotic prophase. Recent attention has been paid to the bouquet formation, a nearly universal event, during which the telomeres cluster on the nuclear membrane in early prophase. It has been suggested that because the telomeres are in close proximity this would enhance their pairing and subsequent synapsis of the homologues. In Arabidopsis we observe that the telomeres are paired homologously in early meiosis whilst still arranged around the nucleolus. They are moved to the nuclear membrane preceding synapsis and reveal only a loose clustering, which may represent a transient bouquet. On completion of synapsis the paired telomeres are dispersed and remain attached to the nuclear membrane until diplotene when they dissociate from the nuclear membrane. We also discuss the prospects for live imaging of the telomeres in Arabidopsis.

To freeze or not to freeze: a cost-effectiveness analysis of wart treatment

BACKGROUND

Several general practitioner (GP)-prescribed and over-the-counter therapies for warts and verrucae are available. However, the cost-effectiveness of these treatments is unknown.

OBJECTIVES

To compare the cost-effectiveness of different treatments for cutaneous warts.

METHODS

We designed a decision-analytic Markov simulation model based on systematic review evidence to estimate the cost-effectiveness of various treatments. The outcome measures studied are percentage of patients cured, cost of treatment and incremental cost-effectiveness ratio for each treatment, compared with no treatment, after 18 weeks.

RESULTS

Duct tape was most cost-effective but published evidence of its effectiveness is sparse. Salicylic acid was the most cost-effective over-the-counter treatment commonly used. Cryotherapy administered by a GP was less cost-effective than GP-prescribed salicylic acid and less cost-effective than cryotherapy administered by a nurse.

CONCLUSIONS

Duct tape could be adopted as the primary treatment for cutaneous warts if its effectiveness is verified by further rigorous trials. Nurse-administered cryotherapy is likely to be more cost-effective than GP-administered cryotherapy.

Effectiveness and cost-effectiveness of salicylic acid and cryotherapy for cutaneous warts. An economic decision model

OBJECTIVES

To estimate the costs of commonly used treatments for cutaneous warts, as well as their health benefits and risk. To create an economic decision model to evaluate the cost-effectiveness of these treatments, and, as a result, assess whether a randomised controlled trial (RCT) would be feasible and cost-effective.

DATA SOURCES

Focus groups, structured interviews and observation of practice. Postal survey sent to 723 patients. A recently updated Cochrane systematic review and published cost and prescribing data.

REVIEW METHODS

Primary and secondary data collection methods were used to inform the development of an economic decision model. Data from the postal survey provided estimates of the effectiveness of wart treatments in a primary care setting. These estimates were compared with outcomes reported in the Cochrane review of wart treatment, which were largely obtained from RCTs conducted in secondary care. A decision model was developed including a variety of over-the-counter (OTC) and GP-prescribed treatments. The model simulated 10,000 patients and adopted a societal perspective.

RESULTS

OTC treatments were used by a substantial number of patients (57%) before attending the GP surgery. By far the most commonly used OTC preparation was salicylic acid (SA). The results of the economic model suggested that of the treatments prescribed by a GP, the most cost-effective treatment was SA, with an incremental cost-effectiveness ratio (ICER) of 2.20 pound/% cured. The ICERs for cryotherapy varied widely (from 1.95 to 7.06 pound/% cured) depending on the frequency of applications and the mode of delivery. The most cost-effective mode of delivery was through nurse-led cryotherapy clinics (ICER = 1.95 pound/% cured) and this could be a cost-effective alternative to GP-prescribed SA. Overall, the OTC therapies were the most cost-effective treatment options. ICERs ranged from 0.22 pound/% cured for OTC duct tape and 0.76 pound/% cured for OTC cryotherapy to 1.12 pound/% cured for OTC SA. However, evidence in support of OTC duct tape and OTC cryotherapy is very limited. Side-effects were commonly reported for both SA and cryotherapy, particularly a burning sensation, pain and blistering.

CONCLUSIONS

Cryotherapy delivered by a doctor is an expensive option for the treatment of warts in primary care. Alternative options such as GP-prescribed SA and nurse-led cryotherapy clinics provide more cost-effective alternatives, but are still expensive compared with self-treatment. Given the minor nature of most cutaneous warts, coupled with the fact that the majority spontaneously resolve in time, it may be concluded that a shift towards self-treatment is warranted. Although both duct tape and OTC cryotherapy appear promising new self-treatment options from both a cost and an effectiveness perspective, more research is required to confirm the efficacy of these two methods of wart treatment. If these treatments are shown to be as cost-effective as or more cost-effective than conventional treatments, then a shift in service delivery away from primary care towards more OTC treatment is likely. A public awareness campaign would be useful to educate patients about the self-limiting nature of warts and the possible alternative OTC treatment options available. Two future RCTs are recommended for consideration: a trial of SA compared with nurse-led cryotherapy in primary care, and a trial of home treatments. Greater understanding of the efficacy of these home treatments will give doctors a wider choice of treatment options, and may help to reduce the overall demand for cryotherapy in primary care.

Control of meiotic recombination in Arabidopsis: role of the MutL and MutS homologues

Immunocytochemistry reveals that the Arabidopsis mismatch repair proteins AtMSH4, AtMLH3 and AtMLH1 are expressed during prophase I of meiosis. Expression of AtMSH4 precedes AtMLH3 and AtMLH1 which co-localize as foci during pachytene. Co-localization between AtMSH4 and AtMLH3 occurs, but appears transient. AtMLH3 foci are not detected in an Atmsh4 mutant. However, localization of AtMSH4 is unaffected in Atmlh3, suggesting that recombination may proceed to dHj (double Holliday junction) formation. Mean chiasma frequency in Atmsh4 is reduced to 1.55 compared with 9.86 in wild-type. In contrast with wild-type, the distribution of residual crossovers in Atmsh4 closely fits a Poisson distribution. This is consistent with a two-pathway model for meiotic crossing-over whereby most crossovers occur via an AtMSH4-dependent pathway that is subject to interference, with the remaining crossovers arising via an interference-independent pathway. Loss of AtMLH3 results in an approx. 60% reduction in crossovers. Results suggest that dHj resolution can occur, but in contrast with wild-type where most or all dHjs are directed to form crossovers, the outcome is biased in favour of a non-crossover outcome. The results are compatible with a model whereby the MutL complex maintains or imposes a dHj conformation that ensures crossover formation.

Physical organization of the major duplication onBrassica oleraceachromosome O6 revealed through fluorescence in situ hybridization withArabidopsisandBrassicaBAC probes

The close relationship between Brassica oleracea and Arabidopsis thaliana has been used to explore the genetic and physical collinearity of the two species, focusing on an inverted segmental chromosome duplication within linkage group O6 of B. oleracea. Genetic evidence suggests that these segments share a common origin with a region of Arabidopsis chromosome 1. Brassica oleracea and Arabidopsis bacterial artificial chromosome probes have been used for fluorescence in situ hybridization analysis of B. oleracea pachytene chromosomes to further characterize the inverted duplication. This has been highly effective in increasing the local resolution of the cytogenetic map. We have shown that the physical order of corresponding genetic markers is highly conserved between the duplicated regions in B. oleracea and the physical lengths of the regions at pachytene are similar, while the genetic distances are considerably different. The physical marker order is also well conserved between Arabidopsis and B. oleracea, with only one short inversion identified. Furthermore, the relative physical distances between the markers in one segment of B. oleracea and Arabidopsis have stayed approximately the same. The efficacy of using fluorescence in situ hybridization, together with other forms of physical and genetic mapping, for elucidating such issues relating to synteny is discussed.Key words: collinearity, cytogenetic map, pachytene chromosomes, Brassica, Arabidopsis.

A strategy to investigate the plant meiotic proteome

The analysis of meiosis in higher plants has benefited considerably in recent years from the completion of the genome sequence of the model plant Arabidopsis thaliana and the development of cytological techniques for this species. A combination of forward and reverse genetics has provided important routes toward the identification of meiotic genes in Arabidopsis. Nevertheless identification of certain meiotic genes remains a challenge due to problems such as limited sequence conservation between species, existence of closely related gene families and in some cases functional redundancy between gene family members. Hence there is a requirement to develop new experimental approaches that can be used in conjunction with existing methods to enable a greater range of plant meiotic genes to be identified. As one potential route towards this goal we have initiated a proteomics-based approach. Unfortunately, the small size of Arabidopsis anthers makes an analysis in this species technically very difficult. Therefore we have initially focussed on Brassica oleracea which is closely related to Arabidopsis, but has the advantage of possessing significantly larger anthers. The basic strategy has been to use peptide mass-finger printing and matrix-assisted laser desorption ionization time of flight mass spectrometry to analyse proteins expressed in meiocytes during prophase I of meiosis. Initial experiments based on the analysis of proteins from staged anther tissue proved disappointing due to the low level of detection of proteins associated with meiosis. However, by extruding meiocytes in early prophase I from individual anthers prior to analysis a significant enrichment of meiotic proteins has been achieved. Analysis suggests that at least 18% of the proteins identified by this route have a putative meiotic function and that this figure could be as high as one-third of the total. Approaches to increase the enrichment of proteins involved in meiotic recombination and chromosome synapsis are also described.

Meiotic chromosome synapsis and recombination in Arabidopsis thaliana; an integration of cytological and molecular approaches

Arabidopsis has emerged as an important model for the analysis of meiosis in Angiosperm plants, creating an interesting and useful parallel to other model organisms. This development has been underpinned by advances in the molecular biology and genetics of Arabidopsis, especially the determination of its entire genome sequence. However, these advances alone would have been insufficient without the development of improved methods for cytological analysis and cytogenetic investigation of meiotic nuclei and chromosomes. A basic descriptive framework of meiosis in Arabidopsis has been established based on these procedures. In addition, molecular cytogenetic and immunocytological techniques have provided supplementary detailed information on some aspects of meiosis. Gene identification and characterization have proceeded in parallel with these developments based on both forward and reverse genetic procedures utilising the considerable range of Arabidopsis genetic and molecular resources, such as T-DNA and transposon tagged lines as well as the genomic DNA database, in combination with cytological analysis. A diverse range of meiotic genes have been identified and analysed by these procedures and in selected cases they have been subjected to detailed functional analysis. This review focuses on genes that are involved in the key meiotic events of chromosome synapsis and recombination.

Partial Diploidization of Meiosis in Autotetraploid Arabidopsis thaliana

Meiosis was analyzed cytogenetically in autotetraploids of Arabidopsis, including both established lines and newly generated autotetraploid plants. Fluorescent in situ hybridization with 5S and 45S rDNA probes was used to identify the different chromosomes at metaphase I of meiosis. Multivalents were observed frequently in all the lines analyzed, but there were significant differences in multivalent frequency not only between the newly generated tetraploids and the established lines but also among the different established lines. The new tetraploids showed high multivalent frequencies, exceeding the theoretical 66.66% predicted by the simple random-end pairing model, in some cases significantly, thus indicating that Arabidopsis autotetraploids have more than two autonomous pairing sites per chromosome, despite their small sizes. The established lines showed fewer multivalents than the new autotetraploids did, but the extent of this reduction was strongly line and chromosome dependent. One line in particular showed a large reduction in multivalents and a concomitant increase in bivalents, while the other lines showed lesser reductions in multivalents. The reduction in multivalents was not uniformly distributed across chromosomes. The smaller chromosomes, especially chromosomes 2 and 4, showed the most marked reductions while the largest chromosome (1) showed virtually no reduction compared to the new tetraploids. It is concluded that the established autotetraploid lines have undergone a partial diploidization of meiosis, but not necessarily genetical diploidization, since their creation. Possible mechanisms for the resulting change in meiotic chromosome behavior are discussed.

Variation in chiasma frequency among eight accessions of Arabidopsis thaliana

Natural variation in meiotic recombination frequency in Arabidopsis thaliana has been assessed by analyzing chiasma frequency variation among a range of geographically and ecologically diverse accessions. Fifty pollen mother cells at metaphase I of meiosis were analyzed from each of eight accessions and fluorescence in situ hybridization was applied to enable identification of all 10 chromosome arms. There was no significant variation in mean chiasma frequency between plants within accessions, but there was significant variation between accessions. Further analysis confirmed this finding and identified two particular accessions, Cvi and Ler, as having chiasma frequencies significantly lower than those of the other accessions. The analysis also revealed that the pattern of chiasma distribution between arms and among chromosomes is not consistent over accessions. Further detailed analyses were conducted on each individual chromosome (1-5) in turn, revealing that chromosome 4, one of the acrocentric chromosomes, is the least variable while the other acrocentric chromosome (2) is the most variable. These findings indicate the existence of recombination regulatory elements in Arabidopsis and we conclude that it may be possible in the future to identify these elements and determine their mode of action. The practical implications of such developments are considerable.

Chromosome instability in Spodoptera frugiperda Sf-9 cell line

Homogeneous cell lines are essential in industry and research if reliable and reproducible data are to be obtained. The Spodoptera frugiperda (Sf-9) cell line routinely used for the production of recombinant proteins was found to be heterogeneous, containing a mixture of diploid and tetraploid cells. Using dilution-cloning techniques, diploid and tetraploid subpopulations were isolated from a Sf-9 parental cell line, and their cytogenetic state was monitored using Vinblastine to arrest cells in mitosis. Flow cytometry was used to obtain a snapshot of the predominant subpopulations present to verify the karyological results. The rate at which clonal populations digress into the heterogeneous state was found to be more rapid for the diploid subpopulation, with the emergence of tetraploid cells after only 11 passages, than for the tetraploid subpopulation, where diploid clones appeared after 18 passages. The chromosomes in both diploid and tetraploid subpopulations as well as the parental cell line were found to spontaneously fragment during growth and expansion processes, giving rise to variable chromosome numbers. DNA analysis of cell lines obtained from laboratories worldwide have shown that the Sf-9 cell line used for the production of many recombinant proteins is cytologically unstable, leading to varying degrees of polyploidal state depending on its culture history and supplier.

Nucleolus-associated telomere clustering and pairing precede meiotic chromosome synapsis in Arabidopsis thaliana

The intranuclear arrangements of centromeres and telomeres during meiotic interphase and early prophase I of meiosis in Arabidopsis thaliana were analysed by fluorescent in situ hybridisation to spread pollen mother cells and embryo-sac mother cells. Meiocyte identification, staging and progression were established by spreading and sectioning techniques, including various staining procedures and bromodeoxyuridine labeling of replicating DNA.

Centromere regions of Arabidopsis are unpaired, widely dispersed and peripherally located in nuclei during meiotic interphase, and they remain unpaired and unassociated throughout leptotene. Eventually they associate pairwise during zygotene, as part of the nucleus-wide synapsis of homologous chromosomes.

Telomeres, by contrast, show a persistent association with the nucleolus throughout meiotic interphase. Variation in telomere signal number indicates that telomeres undergo pairing during this interval, preceding the onset of general chromosome synapsis. During leptotene the paired telomeres lose their association with the nucleolus and become widely dispersed. As the chromosomes synapse during zygotene, the telomeres reveal a loose clustering within one hemisphere, which may represent a degenerate or relic bouquet configuration. We propose that in Arabidopsis the classical leptotene/zygotene bouquet is absent and is replaced functionally by nucleolus-associated telomere clustering.

Chiasma formation in Arabidopsis thaliana accession Wassileskija and in two meiotic mutants

Meiotic chiasmata were analysed in metaphase I pollen mother cells (PMCs) of wild-type Arabidopsis thaliana and in two meiotic mutants. Fluorescence in situ hybridisation (FISH) with 45S rDNA and 5S rDNA as probes was used to identify the five chromosome pairs. A wild-type chiasma frequency of 9.24 per cell was found, consistent with estimated genetic recombination values. Individual bivalent chiasma frequencies varied according to chromosome size; chromosome 1 had the highest mean chiasma frequency (2.14) while the short acrocentric chromosomes had the lowest frequencies (1.54 and 1.56). FISH analysis was extended to two meiotic mutants (asy1 and dsy1) having low residual bivalent and chiasma frequencies. Mutant dsy1 gave no indication of chromosome preference for residual bivalent formation; instead it showed a general reduction in bivalent and chiasma frequencies. In asy1, the longest chromosome (1) had the lowest bivalent frequency and chiasma frequency while the short acrocentric chromosome 2 had the highest frequencies. This chromosome pair may be preferentially involved in synapsis and chiasma formation because of their association with the nucleolus. However, other factors may be operating since the other acrocentric chromosome (4), with similar size and structure to chromosome 2, did not share these chiasma properties.

hMRE11: genomic structure and a null mutation identified in a transcript protected from nonsense-mediated mRNA decay

We showed recently that mutation of the hMRE11 gene identified a new ataxia telangiectasia-like disorder (ATLD). In this report we describe the genomic organization of the hMRE11 gene and the analysis of a promoter region that appears to direct the divergent transcription of hMRE11 and the adjacent gene. The characterization of the genomic organization of the hMRE11 gene allowed us to determine the basis of an apparent null hMRE11 allele present in the mother and two patients in one of our two ATLD families. Polymorphic markers in the hMRE11 gene, including the promoter region, provided evidence that the mutated maternal allele was not deleted. An exon by exon search revealed the presence of a missense mutation in exon 15, the effect of which was to create a premature termination codon. Transcripts derived from the mutant allele were found to be subject to nonsense-mediated mRNA decay (NMD). Therefore, this allele was effectively null, because little if any mRNA from it was available for translation. The ATLD patients carrying this protein-truncating hMRE11 mutation have survived because the null allele they inherited from their mother is present with a missense mutation inherited from their father, which is expressed as normal levels of partially functional MRE11 protein. The mutation in the maternal hMRE11 allele of family 2 was also identified in a further unrelated Italian family with ATLD and also found to be subject to NMD.

Meiotic studies of a human male carrier of the common translocation, t(11;22), suggests postzygotic selection rather than preferential 3:1 MI segregation as the cause of liveborn offspring with an unbalanced translocation

The t(11;22)(q23;q11) translocation is the only non-Robertsonian rearrangement for which there are a large number of unrelated families, apparently with the same breakpoints. These families most often have been ascertained through an abnormal child with the karyotype 47,XX or XY, +der(22) t(11;22)(q23;q11). To explain the high incidence of 3:1 segregants, rarely seen in offspring of carriers of other reciprocal translocations, a number of theoretical models have been suggested. We have used both electron microscope analysis of the synaptonemal complex (SC) and dual-color FISH to investigate the meiotic chromosome behavior in a male carrier of the translocation who has the karyotype 46,XY, t(11;22)(q23;q11). Chromosome synapsis, first-meiotic chiasma configuration, and segregation behavior of this translocation have been analyzed directly. Examination of SCs by electron microscopy showed pachytene-cross formation in 49/50 nuclei. Approximately 50% (26/50) revealed a classical fully synapsed quadrivalent. A proportion of these (10/26), however, showed some central asymmetry, suggesting heterologous synapsis. The remaining cells appeared to have incomplete synapsis. FISH analysis showed only quadrivalents in all 100 metaphase I nuclei. The chiasma frequency was increased within the interstitial segments, in comparison with the same region in normal bivalents. All types of segregation category were found in metaphase II nuclei. There was no indication of preferential 3:1 anaphase I segregation. We conclude that the +der(22) constitution in offspring of carriers of t(11;22)(q23;q11) is not likely to be due to meiotic 3:1 segregation being especially common. Rather, the +der(22) constitution is more likely to be the result of postzygotic selection against other unbalanced karyotypes.

A homologue of the yeast HOP1 gene is inactivated in the Arabidopsis meiotic mutant asy1

Synapsis of homologous chromosomes is a key event in meiosis as it is essential for normal chromosome segregation and is implicated in the regulation of crossover frequency. We have previously reported the identification and cytological characterisation of a T-DNA-tagged asynaptic mutant of Arabidopsis thaliana. We have demonstrated that this mutant, asy1, is defective in meiosis in both males and females. Cloning and nucleotide sequencing of the ASY1 gene has revealed that it encodes a polypeptide of 596 amino acids that exhibits similarity to the HOP1 gene of Saccharomyces cerevisiae, which is known to encode a protein essential for synaptonemal complex assembly and normal synapsis. Expression studies indicate that, in common with a number of other Arabidopsis meiotic genes, ASY1 exhibits low-level expression in a range of plant tissues. Southern analysis coupled with database searching has resulted in the identification of an ASY1 homologue, ASY2. Although asy1 exhibits a strong asynaptic phenotype, a residual low level of synapsis indicates that ASY1 and ASY2 may exhibit a low degree of functional redundancy.

Endotoxin induction of nitric oxide synthase and cyclooxygenase-2 in equine alveolar macrophages

OBJECTIVE

To determine the amount of cyclooxygenase-2 (COX-2) and inducible nitric oxide synthase (iNOS) enzymes induced in vitro in equine alveolar macrophages in response to lipopolysaccharide (LPS). Sample Population-Alveolar macrophages obtained from 12 horses.

PROCEDURE

Alveolar macrophages were collected by bronchoalveolar lavage from 12 horses and incubated for 6 hours with LPS (0.001 to 10 microg/ml) or vehicle. Total RNA was extracted and purified. After first-strand cDNA synthesis, mRNA induction was measured, using a polymerase chain reaction (PCR) technique for COX-2, iNOS, and glyceraldehyde 3-phosphate dehydrogenase. In a second study, cells were incubated with LPS or vehicle for 24 hours. Culture medium was assayed for COX-2 and iNOS activity by determining prostaglandin E2 (PGE2) and total nitrite concentrations, respectively.

RESULTS

Lipopolysaccharide induces COX-2 and iNOS mRNA in equine alveolar macrophages. Sequencing revealed that PCR products for COX-2 and iNOS had a high degree of nucleotide homology with the human sequences (91% COX-2, 93% iNOS). Production of mRNA for COX-2 and iNOS was accompanied by induction of enzyme activity. Comparing PCR fragment production, expression of mRNA for iNOS appeared to be less than that for COX-2. Induction of COX-2, but not iNOS, was LPS-concentration dependent. Conclusion-Lipopolysaccharide induces COX-2 and iNOS in equine macrophages.

CLINICAL RELEVANCE

The induction of iNOS and COX-2 by LPS in equine macrophages suggests these enzymes may be important in the pathophysiology of sepsis. Pharmacologic modulation of iNOS and COX-2 activity may represent a novel therapeutic target in the management of endotoxemia in horses.

Comparative analysis of crossover exchanges and chiasmata in Allium cepa x fistulosum after genomic in situ hybridization (GISH)

Genomic in situ hybridization (GISH) successfully differentiated homoeologous genomes in the inter-specific hybrid Allium cepa x fistulosum, thus allowing the detection of reciprocal crossover events as label exchanges in separating anaphase I chromosomes. Three of the eight chromosome pairs were positively identified by fluorescence in situ hybridization (FISH) to rDNA sequences. There was a general similarity of the GISH-based label exchange frequencies and metaphase I chiasma frequencies, but with a 20% deficit of chiasmata. Reasons for this apparent deficit are discussed. The locations of chiasmata and label exchanges are in broad agreement.

Morphometry of paranasal sinus anatomy in chronic rhinosinusitis: a pilot study

OBJECTIVES

To test the null hypothesis that there is no relationship between anatomical variations around the ostiomeatal complex and a predisposition to chronic rhinosinusitis and to define such variations with increased precision.

DESIGN

Case-control study of anatomical variations in diseased and normal sinuses. Eight homologous landmarks defining the ostiomeatal complex were located on coronal computed tomographic scans, and their x and y coordinates were digitized using image analysis.

SUBJECTS

Ten patients with unilateral sinus disease and 10 subjects without sinus disease (scanned for facial pain) who were selected retrospectively by case-note analysis.

RESULTS

Logistic regression showed that the only significant spatial change predictive of a person with rhinosinusitis was the vertical position of the middle turbinate (P=.04), although this was not confirmed by Wilcoxon testing (P>.10). When examined by sinus, however, the horizontal position of the uncinate process was more laterally placed in persons with rhinosinusitis (P=.01), confirmed on Wilcoxon testing (P=.04), but there was no significant difference when compared with sinuses in persons without rhinosinusitis.

CONCLUSIONS

Our findings suggest that there are no anatomical differences within the ostiomeatal complex between patients with and without rhinosinusitis. Patients with rhinosinusitis, however, are more likely to develop it in the side with a more laterally positioned uncinate process. Further studies, with more patients and more advanced techniques, including thin-plate spline analysis, are indicated.

Substance abuse and the emergency room: programmatic implications

A literature review (1984 to 1995) was conducted to identify cost effective policy implications regarding substance use in the emergency room (ER) and trauma unit. Prevalence rates, ranging from 9% to 47%, vary according to where, when and who is tested. Other drugs, most commonly marijuana, benzodiazepines and cocaine, follow a similar pattern to alcohol. The optimal method of measuring substance use depends on the goal of the assessment and a combination of clinical, self-report and biochemical markers is recommended. Simple screening questions such as the TWEAK or AUDIT should be routinely used with all attendants and further assessment provided only when high risk factors have been identified. These include: males, younger patients, metropolitan centres, after midnight and on weekends, injury from violence, accidents including MVAs, high acuity and psychiatric morbidity. Further, this screening should be complimented by an intervention, referral and treatment resource for those in need.

Cytological characterization of four meiotic mutants of Arabidopsis isolated from T-DNA-transformed lines

A secondary screen of the Feldmann collection of T-DNA transformed Arabidopsis lines identified several meiotic mutants. We used a spreading technique combined with DAPI staining in a detailed cytogenetic analysis of meiotic chromosome behaviour in four of these mutants, all of which are putatively T-DNA tagged and therefore candidates for molecular and functional analysis of the mutated genes. Two of them are defined as 'synaptic' mutants, showing greatly reduced association of homologous chromosomes at metaphase I: one is asynaptic, showing failure of synapsis during prophase I, whereas the other is desynaptic and is characterized by normal but non-maintained synapsis. Another mutant is defective in meiotic cell cycle control and undergoes a third meiotic division, resembling a second division but without an additional round of chromosome duplication. A further mutant shows meiosis-limited chromosome disruption, resulting in extensive chromosome fragmentation combined with other defects. All four mutants experience very irregular chromosome distribution during the meiotic divisions, resulting in abnormal numbers and/or sizes of microspores, with resulting reduced fertility.

Neutralization titres of HIV-1-specific monoclonal antibodies vary according to the batch of primary human peripheral blood lymphocytes, but do not vary coordinately

Human peripheral blood lymphocytes (PBL) were collected from five healthy adults under standard conditions and on a number of different occasions, and used in neutralization assays of human immunodeficiency virus type 1 (HIV-1) strain IIIB with three monoclonal antibodies (mAbs). Variations in neutralization titre were observed with different batches of PBLs with, for example, titres of ICR39.3b ranging from 1/10 to over 1/40000. However titres were as high, or higher, in PBLs than in C8166 cells (a human CD4+ T lymphoblastoid cell line) in 82% (28/34) of tests made. Most surprising was that neutralization by the three mAbs did not vary coordinately. In one batch of PBLs the neutralization titre of one of the mAbs might be increased while that of another mAb did not increase, or decrease. Thus PBLs could not be described as giving high or low levels of neutralization without reference to a specific mAb. This was not an assay problem as infectivity titres were relatively constant (varying by 1 to 1.4 fold with respect to C8166 cells), and neutralization titres were reproducible with the same batch of frozen PBLs over a three month period. Only one donor gave consistently low neutralization titres (defined here as 1/200; 2/2 batches tested) with all three mAbs, but all other donors gave similarly low titres with one of their batches of PBLs. The non-coordinate variation in neutralization titre indicates the advisability of using antibodies of several different specificities in any kind of preventive or therapeutic immunity.

A human IgG1 (b12) specific for the CD4 binding site of HIV-1 neutralizes by inhibiting the virus fusion entry process, but b12 Fab neutralizes by inhibiting a postfusion event

The human b12 IgG1, specific for the CD4 binding site of the gp120 of HIV-1, was prepared by recombinant DNA technology. It had a high neutralization rate constant (-3.5 x 10(5) M(-1) sec(-1)), although this is about 10-fold less than the values for the best poliovirus or influenza A virus MAbs. The recombinant b12 Fab neutralized well, with about one-tenth of the activity of b12 IgG. The mechanisms by which b12 IgG1 and its Fab neutralize HIV-1 IIIB on C8166 cells have been investigated. Neither inhibited attachment of virus to the target cell as judged by FACS, immunofluorescence, and ELISA data. This was controlled using MAb F105, another human IgG1, that did neutralize by inhibiting attachment under our conditions. The interactions of b12 IgG- and Fab-neutralized virions with target cells were compared with those of nonneutralized virus using a number of different techniques (fluorescence dequenching of R18-labeled virions, immunofluorescence of virion gp41 and p24 antigens, and acquisition of resistance to removal of virions from the cell by protease). These and the inhibition of HIV-1-mediated cell-cell fusion all demonstrated that b12 IgG neutralized by inhibiting the primary fusion-uncoating mechanism. However, the interactions of b12 Fab-neutralized and nonneutralized virions with C8166 cells were indistinguishable. Thus b12 Fab did not inhibit fusion uncoating, and by inference inhibited a stage of infection that occurs after the entry of the virion core into the cytoplasm. It is therefore possible that b12 IgG kills HIV-1 twice over, by fusion-inhibition and by inhibiting the postentry event proposed for the Fab. The mechanism of neutralization of b12 Fab and of other MAbs that neutralize in a similar way and why b12 Fab and IgG neutralize by different mechanisms are discussed.

Different strategies of X-inactivation in germinal and somatic cells: histone H4 underacetylation does not mark the inactive X chromosome in the mouse male germline

It has previously been shown by immunocytochemistry that the inactive X chromosome (Xi) in somatic cells of human and mouse females is marked by underacetylation of histone H4. It has been suggested that this may be important for transcriptional silencing of genes on Xi. We have now investigated X-inactivation in meiotic cells of the male germline. In these cells the single X chromosome is transcriptionally inactive and expresses XIST, a gene that in somatic cells is transcribed only from Xi. By immunostaining with antibodies to H4 acetylated at lysines 5, 8, 12, or 16, we demonstrate that histone H4 on the male X is not underacetylated. We conclude that there is a differential germline strategy for maintenance of X-inactivation and that H4 underacetylation, though associated with the long-term marking of inactive X chromosomes in the female soma, is not always essential for the transcriptional down-regulation of X-linked genes.

Two neutralizing anti-V3 monoclonal antibodies act by affecting different functions of human immunodeficiency virus type 1

Monoclonal antibody (MAb) ICR41.1i (rat IgG2a) is specific for a conformation-dependent epitope of human immunodeficiency virus type 1 (HIV-1) V3 , and MAb F58 (mouse IgG1) recognizes the peptide IXXGPGR, at the tip of the V3 loop. Both MAbs neutralized HIV-1 strain IIIB in C8166 and HeLa-T4(CD4) cells. Neutralization by either MAb did not inhibit attachment of virus to target cells as determined by FACS analysis, ELISA or immunofluorescence, and such attachment was absolutely dependent on the availability of CD4 molecules. F58 inhibited virus-induced cell-cell fusion, and reduced internalization of virions in direct proportion to neutralization. In contrast, ICR41.li had no effect on HIV-1-mediated cell fusion or on internalization of virus. It was concluded that MAb F58 neutralized infectivity by inhibiting fusion of the virus with the cell and internalization of the viral core, and that ICR41.1i neutralized by inhibiting a post-fusion-internalization event. The possible mechanism by which a neutralizing antibody binds to the V3 loop and affects the function(s) of structures inside the virion is discussed. Lastly, postattachment neutralization (PAN) was investigated. F58 mediated PAN at 21 degrees C and 35 degrees C. However, ICR41.1i gave PAN at 21 degrees C but not at 35 degrees C, suggesting that a temperature-dependent event affecting the V3 loop had abrogated neutralization. Overall, it appears that antibodies to different epitopes within the V3 loop neutralize by affecting very different functions of the virus.

Relationship between physical signs of elbow dysplasia and radiographic score in growing Rottweilers

OBJECTIVE

To examine the relationship between physical signs of elbow dysplasia and radiographic appearance of the elbow joints in growing dogs.

DESIGN

Prospective study.

ANIMALS

55 Rottweiler pups.

PROCEDURE

Owners of clinically normal Rottweiler pups were contacted through breed clubs in 3 Australian states and asked to participate in the study. All those offering to participate were included.

PROCEDURE

The first physical examination was performed when pups were 3 months old and included a lameness evaluation and palpation of the elbow joints. Physical examinations were repeated when pups were 5, 6, 9, and 12 months old. Radiographs of the elbows were obtained at 6 and 12 months. Relationships among lameness, decreased range of movement, signs of pain, and radiographic data related to elbow dysplasia were examined.

RESULTS

Elbow dysplasia caused clinical lameness in only 3 dogs but 57% of dogs developed radiographic signs of elbow dysplasia by 12 months of age. A grade-2 radiographic score at 12 months of age was significantly associated with clinical elbow dysplasia.

CLINICAL IMPLICATIONS

Elbow dysplasia has a prevalence of > 50% in certain breed populations. This study supports radiographic screening at 12 months of age, accompanied by physical examination to detect clinical elbow dysplasia.

Varying temperature-dependence of post-attachment neutralization of human immunodeficiency virus type 1 by monoclonal antibodies to gp 120: identification of a very early fusion-independent event as a neutralization target

Neutralization of human immunodeficiency virus type 1 by adding antibody after the virus has attached to the host cell (post-attachment neutralization:PAN) was investigated using three rat monoclonal antibodies (MAbs) directed against the outer domain of the membrane protein, gp 120. Two of the MAbs are specific for the CD4-binding site region and one for the V3 loop. MAb ICR39.13g (CD4-binding site region-specific; IgG2b) effected PAN efficiently at temperatures from 4 to 35 degree C. MAb ICR41.1i (V3 loop-specific; IgG2c) effected PAN only at temperatures of 24 degree C and below. This suggests that its V3 epitope is masked by a change in gp 120 which occurs at temperatures > or = 26 degree C, or that the virion function which is inhibited by ICR41.1i and is responsible for neutralization has already operated at > or = 26 degree C. Resistance to neutralization by ICR41.1i occurred within 20 min of shifting the temperature up to 35 degree C. Finally, MAb ICR39.3b (CD4-binding site region-specific; IgG2b) did not give PAN at any temperature, indicating that neutralization can only occur if this MAb binds virus before it attaches to the cell. Thus, these studies identify at least one novel fusion-independent event, the neutralization target of a V3 MAb, which occurs very early in the initial stages of virus-cell interaction.

Topographical variation within the articular cartilage and subchondral bone of the normal ovine knee joint: a histological approach

Topographical variation in the articular cartilage and subchondral bone of the normal ovine knee was examined using histological techniques. The articular cartilage was examined grossly, then histological sections were cut and the cartilage thickness and chondrocyte density were measured. Bone mineral density, thickness of the subchondral bone plate (SBP) and volume and surface histomorphometrical parameters and mineral apposition rate were calculated for the subchondral bone. It was found that the articular cartilage on the tibial plateaux was thicker, less cellular, and overlay a thicker SBP than that on the femoral condyles. Similarly, the cartilage in the medial joint compartments was thicker, less cellular and overlying a thicker less dense SBP than that in the lateral joint compartments. There was no variation in bone histomorphometric parameters or mineral apposition rate between regions. Biomechanical testing has shown that loading is not uniform throughout the normal human knee joint. The present results suggest that loading within the ovine knee is also nonuniform, with the central regions of the tibial plateaux bearing greater loads than the femoral condyles, and the medial joint compartment being loaded more than the lateral one. The articular cartilage and subchondral bone have adapted in order to best withstand these variations in loading. These histological findings, plus the topographical variations in cartilage biochemistry reported by Read et al. (Topographical variation in composition, PG-biosynthesis and swelling pressure of cartilages of loaded tibio-femoral joints (Abstract). Proceedings of the Combined Meeting of the Orthopaedic Research Societies of USA, Japan and Canada.(ABSTRACT TRUNCATED AT 250 WORDS)

XY chromosome behaviour in the germ-line of the human male: a FISH analysis of spatial orientation, chromatin condensation and pairing

We have used multicolour fluorescence in situ hybridization to study the behaviour of the X and Y chromosomes in relation to a representative autosome, chromosome 1, on air-dried testicular preparations from normal fertile human males. In a proportion of Sertoli cells at interphase as well as spermatogonial metaphases there is an apparent selective undercondensation of the heterochromatic block of the long arm of the Y, which may be of functional significance with respect to Y-specific gene activity, initiating and maintaining spermatogenesis; we suggest that this may involve a mechanism similar to heterochromatin position-effect variegation in Drosophila. In the supporting Sertoli as well as pre-meiotic and leptotene cells the X and Y occupy relatively restricted domains at opposite poles of the nuclear membrane, while the chromosome 1 centromere regions are located interstitially and appear prealigned. The XY pairing and 'sex vesicle' formation comprises a complex series of spatial movement and differential condensation patterns. On the basis of these observations we propose that: the XIST/Xist gene, known to be involved in somatic X inactivation, imposes a chromatin reorganization leading to bending at the X-inactivation centre both at first meiotic prophase in males and in the soma in females; and the differential X and Y segments are protected from potentially deleterious meiotic exchanges by their separate spatial orientation. In addition, there is an indication that the timing of pairing and first meiotic segregation of the sex chromosomes is different, and precocious in comparison to the pairing and segregation of the autosomes, which may explain the high incidence of sex chromosome aneuploidy in sperm.

Moderate exercise exacerbates the osteoarthritic lesions produced in cartilage by meniscectomy: a morphological study

Unilateral medial meniscectomy was performed on two groups of sheep. At 1 week post-operatively, one group (N = 5) underwent a regimen of moderate walking exercise (24 km/week), while the other group (N = 5) received no exercise. Two groups (N = 6 and 8) of unoperated sheep were used as exercised and unexercised controls for the respective meniscectomized groups. Six months post-surgery all groups were sacrificed and their knee joints were examined macroscopically using established scoring systems. In both groups, meniscectomy induced cartilage and bone changes typical of early hypertrophic osteoarthritis. However, meniscectomized animals subjected to the exercise program developed more severe cartilage lesions and osteophytes than their unexercised counterparts. While the cell density in femoral cartilage of the meniscectomized and exercised group was similar to controls, that of the meniscectomized but unexercised animals was higher. We conclude form these data that in this animal model exercise exacerbated the lesions induced in articular cartilage by meniscectomy.

Review of the use of MRI in soft tissue lesions

The MR images of 34 patients with soft tissue lesions were retrospectively evaluated to assess the accuracy of the technique in distinguishing benign from malignant lesions, and to assess the usefulness of various criteria in making this distinction. The overall sensitivity for the detection of malignancy was 75% with a specificity of 94%. Size of lesion was found to be a good criterion in predicting malignancy, lesion margin and signal intensity were less useful. The tissue type was determined in a few instances where signal characteristics were typical, notably lipomas and neural tumours, but this was not reliable and in most lesions the tissue of origin cannot be determined on MR imaging and biopsy is necessary.

Mechanisms of neutralization of a nairovirus (Dugbe virus) by polyclonal IgG and IgM

Dugbe virus is a member of the nairovirus genus of the Bunyaviridae. Purified polyclonal anti-Dugbe virus IgG, which neutralized greater than 99.5% of virus, reduced attachment of virus to BSC-1 cell monolayers by only 36%. A 100-fold lower concentration neutralized virus by 88%, and had no effect upon attachment. Neutralizing IgG did not affect the ability of Dugbe virus to be internalized by or to fuse with BSC-1 cells. This suggests that IgG neutralization occurs largely at a stage subsequent to primary uncoating. Purified polyclonal anti-Dugbe virus IgM neutralized infectivity and had no effect on the attachment of virus to cells, but inhibited internalization of virus by about 50%. Thus IgM neutralizes partly by interfering with entry of virus and partly by a post-entry event. Neutralization by intermediate concentrations of IgM was enhanced 20-fold in the presence of complement. At high concentrations of IgM, complement-dependent neutralization declined. This is probably due to IgM binding in a planar rather than crab conformation, which does not expose the complement binding sites. Aggregation occurred only at relatively low concentrations of immunoglobulin. Electron microscopy and reactivation of infectivity by vortexing suggested that aggregation makes only a minor contribution to neutralization by IgG or IgM.

Incidence and clinical significance of sesamoid disease in rottweilers

A group of 55 rottweiler pups was studied from three to 12 months old to assess the incidence and clinical significance of disease involving the palmar metacarpal sesamoid bones. The results of physical examination were correlated with clinical signs of lameness and the results of radiographic examination of the forefeet. Twenty-one dogs became lame during the study and in 12 of them the lameness was attributable to sesamoid disease. However by 12 months of age, the incidence of sesamoid disease as assessed by radiographic changes in the sesamoid bones was 73 per cent (30 of 41 dogs). Six of the 12 dogs which were lame owing to sesamoid disease got better without specific treatment. It was concluded that sesamoid disease can result in clinical lameness in young rottweilers, but that subclinical disease is common.

Neutralization of influenza virus by low concentrations of hemagglutinin-specific polymeric immunoglobulin A inhibits viral fusion activity, but activation of the ribonucleoprotein is also inhibited

High concentrations of hemagglutinin-specific neutralizing polymeric monoclonal immunoglobulin A (IgA) inhibit attachment of the majority of type A influenza virus virions to cell monolayers and tracheal epithelium (H. P. Taylor and N. J. Dimmock, J. Exp. Med. 161:198-209, 1985; M. C. Outlaw and N. J. Dimmock, J. Gen. Virol. 71:69-76, 1990). A minority of virions attaches but is not infectious. Here, we report that a different mechanism operates when influenza virus A/Puerto Rico/8/34 (H1N1) is neutralized by low concentrations of monoclonal polymeric IgA or when A/fowl plague virus/Rostock/34 (H7N1) is neutralized by low concentrations of polyclonal rat secretory IgA. Under these conditions, neutralized virus attaches to cells and is taken up by them. However, upon entering the cell, the nucleoprotein (NP) of neutralized virus is found in the perinuclear cytoplasm, whereas NP from nonneutralized virus is concentrated in the nucleus itself. Further data show that the low-pH-mediated cell fusion activity of virions is inhibited by IgA in proportion to loss of infectivity. The possibilities that neutralization by low amounts of polymeric IgA is caused by inhibition of the virion fusion activity and that the aberrant distribution of NP from neutralized virus results from its failure to escape from the endosomal system were investigated by using A/PR/8/34 and the fusogenic agent polyethylene glycol (PEG) at pH 5.4. A/PR/8/34 attached to cells at 4 degrees C, with minimal internalization of the virus; treatment with PEG at pH 5.4 and 4 degrees C for 1 min led to infectious fusion of nonneutralized virus with the plasma membrane and, under these conditions, was more efficient than PEG at pH 7 or medium at pH 5.4. Neutralized virus which was attached to cells and treated with acidified PEG appeared to undergo primary and secondary uncoating, with its NP protein becoming concentrated in the nucleus and M1 becoming concentrated in the perinuclear cytoplasm. Although the distribution of NP and M1 was indistinguishable from infectious virus, infectivity was not restored. Thus, even when IgA-induced inhibition of fusion is reversed, virus is still neutralized. We suggest that infectious influenza virus undergoes an activation stage which may be the relaxation of the ribonucleoprotein structure needed to permit transcription or may be the removal of M1 bound to the ribonucleoprotein.(ABSTRACT TRUNCATED AT 400 WORDS)

Rat peritoneal neutrophils selectively relax vascular smooth muscle

A vascular relaxing factor from oyster glycogen-elicited rat peritoneal neutrophils has been shown previously to possess a pharmacologic profile similar to that described for endothelium-derived-relaxing factor. The present experiments were designed to determine the in vitro tissue and species selectivity effects of the neutrophil-derived nitric oxide. Neutrophils (1 x 10(5) to 1 x 10(8) cells/10-ml organ chamber) were added to organ chambers filled with a physiological salt solution (37 degrees C; pH 7.4; 21% O2; 100 U/ml of superoxide dismutase) containing a ring or strip of an isolated tissue contracted with an appropriate contractile agent. Neutrophils caused relaxations in all vascular tissues tested, with the dog coronary artery being the most sensitive (IC50 approximately 1 x 10(5) cells), followed by the dog femoral artery, rabbit aorta and dog saphenous vein, respectively. In the rabbit fundic strip, approximately 1 x 10(7) cells were required to induce 50% relaxation, with 1 x 10(8) cells producing less than 35% relaxation in the dog, guinea pig and rat tracheas. In contrast, nitroprusside- and cromakalim-induced relaxations in all the smooth muscle tissues tested. The response to cromakalim was similar in all tissues with nitroprusside being more active in the vascular tissues. Methylene blue (1 x 10(-5) M) abolished the neutrophil induced relaxations in the rabbit aorta and dog femoral artery but had no effect on the responses to nitroprusside or cromakalim in the rabbit aorta, dog femoral artery or guinea pig trachea. Neutrophils, nitroprusside and cromakalim had limited effects on the spontaneously beating guinea pig right atria.(ABSTRACT TRUNCATED AT 250 WORDS)

Rhabdomyosarcoma associated with familial adenomatous polyposis

We report a case of a 16 year old girl with orbital rhabdomyosarcoma who during chemotherapy developed bloody diarrhoea. On investigation she was found to have multiple colonic polyps. Cytogenetic analysis has shown a pattern typical of familial adenomatous polyposis. We present a review of the literature concerning the associations of familial adenomatous polyposis. The association of familial adenomatous polyposis with rhabdomyosarcoma has not been previously reported.

Mechanisms of neutralization of influenza virus in tracheal epithelial and BHK cells vary according to IgG concentration

The interaction of IgG-neutralized type A influenza virus with differentiated epithelial cells of mouse trachea, BHK cells, and chicken erythrocytes was studied using three mouse monoclonal antibodies (IgG2a) each directed against a different antigenic site on the hemagglutinin. At high HIU:HAU ratios virus was neutralized greater than 99%, monodisperse, and attached to tracheal epithelial and BHK cells in normal amounts. The majority (70-80%) of neutralized virus failed to attach to erythrocytes. At low HIU:HAU ratios the virus was aggregated by each of the antibodies, and attachment to tracheal epithelial and BHK cells was inhibited by up to 75%. Combined aggregation and inhibition of attachment could theoretically account for up to 96% loss of infectivity but this corresponded with the observed degree of neutralization with only one of the antibodies. With increasing antibody:virus ratios, aggregation and inhibition of attachment contributed ever diminishingly to the observed neutralization and eventually not at all. Both neutralized and infectious virus attached to neuraminidase-sensitive receptors. After attachment neutralized virus became increasingly resistant to removal by neuraminidase suggesting that it had been internalized by the cell.

Morphological studies of the neutralization of influenza virus by IgM

Quantitative relationships between neutralization, aggregation and attachment to monolayers of chick embryo fibroblast (CEF) cells have been studied using a constant amount of influenza A/fowl plague virus/Rostock/34 (H7N1) and varying amounts of purified mouse polyclonal IgM directed against the haemagglutinin, the major viral neutralization antigen. There are two major types of interaction. (i) At low concentrations of IgM there is aggregation of virus, but no neutralization provided that the aggregates are dispersed by vortexing and dilution. Maximum aggregation occurs at less than seven molecules of IgM per virion and the IgM is probably bound in the 'staple' or 'crab' conformation at these concentrations. (ii) At higher concentrations there is neutralization and this coincides with inhibition of attachment of virus to CEF cells. Neutralization of 50% infectivity requires about 35 molecules of IgM per virion. The maximum neutralization observed was only 87%. Quantitative data and electron microscopy observations suggest that molecules of IgM at the higher concentrations adopt a planar stance approximately perpendicular to the viral surface. It appears that IgM neutralizes fowl plague virus in vitro primarily by interfering with its attachment to cells; the fraction of neutralized virus that does attach is known not be internalized.