Leptospiral uveitis - there is more to it than meets the eye!

Leptospirosis, caused by pathogenic species of genus Leptospira, is a highly prevalent zoonotic disease throughout many parts of the world, and an important emerging disease within the United States. Uveitis is a common complication of systemic infection in humans. A similar condition in horses is characterized by recurrent bouts of inflammation. In this article, we review advances in our understanding of leptospiral uveitis and its pathogenic mechanisms.

Elimination of arctic variant rabies in red foxes, metropolitan Toronto

To control the arctic variant of rabies virus in red foxes, 332,257 bait doses containing live, attenuated Evelyn-Rokitnicki-Abelseth rabies vaccine were distributed in greater metropolitan Toronto during 1989–1999. Human and pet contact with bait was minimal, and no adverse reactions to the vaccine were noted. Significantly fewer rabid foxes were found during the 17 years after fox baiting (5 cases during 1990–2006) than in the 17 years before (96 cases during 1973–1989). The last report of a rabid fox in metropolitan Toronto was in 1996 (reporting period through September 2006), which confirms that distributing oral rabies vaccine bait is a feasible tactic for the control of rabies in foxes in urban environments.

GABA-benzodiazepine receptor function in alcohol dependence: a combined 11C-flumazenil PET and pharmacodynamic study

RATIONALE

Gamma-aminobutyric acid (GABA)-benzodiazepine receptor function is hypothesised to be reduced in alcohol dependence.

OBJECTIVES

We used positron emission tomography (PET) with [11C]flumazenil, a non-selective tracer for brain GABA-benzodiazepine (GABA-BDZ) receptor binding, to determine in vivo the relationship between BDZ receptor occupancy by an agonist, midazolam, and its functional effects.

METHODS

Abstinent male alcohol dependent subjects underwent [11C]flumazenil PET to measure occupancy of BDZ receptors by midazolam whilst recording its pharmacodynamic effects on behavioural and physiological measures. Rate constants describing the exchange of [11C]flumazenil between the plasma and brain compartments were derived from time activity curves.

RESULTS

A 50% reduction in electroencephalography (EEG)-measured sleep time was seen in the alcohol dependent group despite the same degree of occupancy by midazolam as seen in the control group. The effects of midazolam on other measures of benzodiazepine receptor function, increasing EEG beta1 power and slowing of saccadic eye movements, were similar in the two groups. No differences in midazolam or flumazenil metabolism were found between the groups.

CONCLUSIONS

In summary, our study suggests that alcohol dependence in man is associated with a reduced EEG sleep response to the benzodiazepine agonist, midazolam, which is not explained by reduced BDZ receptor occupancy, and is consistent with reduced sensitivity in this measure of GABA-BDZ receptor function in alcohol dependence. The lack of change in other functional measures may reflect a differential involvement of particular subtypes of the GABA-BDZ receptor.

Borrelia burgdorferi RevA antigen is a surface-exposed outer membrane protein whose expression is regulated in response to environmental temperature and pH

Borrelia burgdorferi, the causative agent of Lyme disease, produces RevA protein during the early stages of mammalian infection. B. burgdorferi apparently uses temperature as a cue to its location, producing proteins required for infection of warm-blooded animals at temperatures corresponding to host body temperature, but does not produce such virulence factors at cooler, ambient temperatures. We have observed that B. burgdorferi regulates expression of RevA in response to temperature, with the protein being synthesized by bacteria cultivated at 34 degrees C but not by those grown at 23 degrees C. Tissues encountered by B. burgdorferi during its infectious cycle vary in their pH values, and the level of RevA expression was also found to be dependent upon pH of the culture medium. The cellular localization of RevA was also analyzed. Borrelial inner and outer membranes were purified by isopycnic centrifugation, and membrane fractions were conclusively identified by immunoblot analysis using antibodies raised against the integral inner membrane protein MotB and outer membrane-associated Erp lipoproteins. Immunoblot analyses indicated that RevA is located in the B. burgdorferi outer membrane. These analyses also demonstrated that an earlier report (H. A. Bledsoe et al., Infect. Immun. 176:7447-7455, 1994) had misidentified such B. burgdorferi membrane fractions. RevA was further demonstrated to be exposed to the external environment, where it could facilitate interactions with host tissues.

Analysis of Borrelia burgdorferi gene expression during life cycle phases of the tick vector Ixodes scapularis

Borrelia burgdorferi exists in nature via an enzootic cycle whereby the organism must adapt to the diverse environmental conditions provided inside the arthropod transmission vector and the mammalian reservoir hosts. B. burgdorferi genes shown to be regulated by temperature, pH and/or cell density during the organism's growth in culture medium were assayed for expression during various stages of the tick feeding cycle by reverse transcription-polymerase chain reaction (RT-PCR). ospA, ospC, flaB, erpA/I/N, erpB/J/O, rev and mlpA, were transcriptionally active following the larval and nymphal stages of feeding as determined by qualitative RT-PCR. During tick resting periods between feedings, ospC, mlpA and rev transcription were undetectable, in contrast to ospA, flaB, erpA/I/N and erpB/J/O. bba64, a gene induced by environmental changes in culture and expressed during mammalian infection, was not detectable during any of the tick life cycle phases. Quantitative PCR to determine B. burgdorferi genome equivalents in these tick samples using DNA co-purified with the RNA allowed an estimation of gene expression relative to the numbers of B. burgdorferi present in the ticks. Although the spirochete totals varied widely between individual tick pools of fed, replete nymphs, the relative expression ratios between individual target genes following a nymphal feed were comparable. Similarly, borrelial gene transcription from the larval feeding and the nymphal feeding were observed and compared. These findings analogize B. burgdorferi gene expression observed by environmental stimuli in vitro with the transcriptional activity occurring during the organism's infectious cycle within the tick.

Distinct regulatory pathways control expression of Borrelia burgdorferi infection-associated OspC and Erp surface proteins

Deciphering the mechanisms by which Borrelia burgdorferi controls the synthesis of proteins associated with mammalian infection will be an important step toward understanding the pathogenic properties of Lyme disease-causing bacteria. We present results of studies indicating that B. burgdorferi senses a wide variety of environmental stimuli, including soluble chemicals, which enables it to independently control synthesis of the Erp and OspC proteins. Regulation of OspC and Erp expression appears to occur at the level of transcription. In this regard, we observed that one or more DNA-binding proteins interact specifically with erp promoter DNA but not with the ospC promoter.

The Arabidopsis HOS1 gene negatively regulates cold signal transduction and encodes a RING finger protein that displays cold-regulated nucleo--cytoplasmic partitioning

Low temperature is one of the most important environmental stimuli that control gene transcription programs and development in plants. In Arabidopsis thaliana, the HOS1 locus is a key negative regulator of low temperature-responsive gene transcription. The recessive hos1 mutation causes enhanced induction of the CBF transcription factors by low temperature as well as of their downstream cold-responsive genes. The hos1 mutant plants flower early, and this correlates with a low level of Flowering Locus C gene expression. The HOS1 gene was isolated through positional cloning. HOS1 encodes a novel protein with a RING finger motif near the amino terminus. HOS1 is ubiquitously expressed in all plant tissues. HOS1--GFP translational fusion studies reveal that HOS1 protein resides in the cytoplasm at normal growth temperatures. However, in response to low temperature treatments, HOS1 accumulates in the nucleus. Ectopic expression of HOS1 in wild-type plants causes cosuppression of HOS1 expression and mimics the hos1 mutant phenotypes.

Temperature-regulated protein synthesis by Leptospira interrogans

Leptospira interrogans is an important mammalian pathogen. Transmission from an environmental source requires adaptations to a range of new environmental conditions in the organs and tissues of the infected host. Since many pathogenic bacteria utilize temperature to discern their environment and regulate the synthesis of appropriate proteins, we investigated the effects of temperature on protein synthesis in L. interrogans. Bacteria were grown for several days after culture temperatures were shifted from 30 to 37 degrees C. Triton X-114 cellular fractionation identified several proteins of the cytoplasm, periplasm, and outer membrane for which synthesis was dependent on the culture temperature. Synthesis of a cytoplasmic protein of 20 kDa was switched off at 37 degrees C, whereas synthesis of a 66-kDa periplasmic protein was increased at the higher temperature. Increased synthesis of a 25-kDa outer membrane protein was observed when the organisms were shifted from 30 to 37 degrees C. A 36-kDa protein synthesized at 30 but not at 37 degrees C was identified as LipL36, an outer membrane lipoprotein. In contrast, expression of another lipoprotein, LipL41, was the same at either temperature. Immunoblotting with convalescent equine sera revealed that some proteins exhibiting thermoregulation of synthesis elicited antibody responses during infection. Our results show that sera from horses which aborted as a result of naturally acquired infection with L. interrogans serovar pomona type kennewicki recognize periplasmic and outer membrane proteins which are differentially synthesized in response to temperature and which therefore may be important in the host-pathogen interaction during infection.

A second allele of eppA in Borrelia burgdorferi strain B31 is located on the previously undetected circular plasmid cp9-2

Although sequence analysis of Borrelia burgdorferi isolate B31 was recently declared "complete," we found that cultures of this strain can contain a novel 9-kb circular plasmid, cp9-2. The newly described plasmid contains both sequence similarities with and differences from the previously identified B31 plasmid cp9-1 (formerly cp9). cp9-1 and cp9-2 each encode a unique allele of EppA, a putative membrane protein synthesized by B. burgdorferi during mammalian infection.

Repetition, conservation, and variation: the multiple cp32 plasmids of Borrelia species

Members of the spirochete genus Borrelia contain large numbers of extrachromosomal DNAs. Sequence analysis of the B. burgdorferi strain B31 genome indicated that its many plasmids contain large quantities of repeated sequences, the most obvious of which are the cp32 plasmid family. Individual spirochetes may carry nine or more different, but homologous, cp32 plasmids. Every other species of Borrelia examined thus far also contains multiple plasmids related to the B. burgdorferi cp32s. These plasmids are arguably the best characterized of all the borrelial plasmids, and epitomize the apparent redundancy evident in the many plasmids carried by these bacteria. Despite their extensive similarities, cp32 plasmids contain some open reading frames whose sequences often vary between plasmids, and which encode proteins synthesized by the bacteria during vertebrate infection. In this review, we analyze the hypervariable and conserved regions of the cp32 plasmid family, and discuss possible reasons why borreliae harbor multiple gene paralogs.

The relapsing fever spirochete Borrelia hermsii contains multiple, antigen-encoding circular plasmids that are homologous to the cp32 plasmids of Lyme disease spirochetes

Borrelia hermsii, an agent of tick-borne relapsing fever, was found to contain multiple circular plasmids approximately 30 kb in size. Sequencing of a DNA library constructed from circular plasmid fragments enabled assembly of a composite DNA sequence that is homologous to the cp32 plasmid family of the Lyme disease spirochete, B. burgdorferi. Analysis of another relapsing fever bacterium, B. parkeri, indicated that it contains linear homologs of the B. hermsii and B. burgdorferi cp32 plasmids. The B. hermsii cp32 plasmids encode homologs of the B. burgdorferi Mlp and Bdr antigenic proteins and BlyA/BlyB putative hemolysins, but homologs of B. burgdorferi erp genes were absent. Immunoblot analyses demonstrated that relapsing fever patients produced antibodies to Mlp proteins, indicating that those proteins are synthesized by the spirochetes during human infection. Conservation of cp32-encoded genes in different Borrelia species suggests that their protein products serve functions essential to both relapsing fever and Lyme disease spirochetes. Relapsing fever borreliae replicate to high levels in the blood of infected animals, permitting direct detection and possible functional studies of Mlp, Bdr, BlyA/BlyB, and other cp32-encoded proteins in vivo.

The introduction of patient process re-engineering in the Peterborough Hospitals NHS Trust

Patient process recognition and re-engineering (PPR) has become a major concern of recent health care development and management. This paper discusses the position of the National Health Service (NHS) in the UK; where it is at present and where it aims to be. It suggests that the work of the current government in developing community care is central to the work of both the Leicester Royal Infirmary and the Peterborough Hospitals NHS Trust, when building relationships between primary (community) and secondary (hospital) health care provision. This paper aims to examine whether and how PPR can improve patient processes in the NHS. It does this through a case study of PPR in Peterborough Hospital.

Efficient targeted mutagenesis in Borrelia burgdorferi

Genetic studies in Borrelia burgdorferi have been hindered by the lack of a nonborrelial selectable marker. Currently, the only selectable marker is gyrB(r), a mutated form of the chromosomal gyrB gene that encodes the B subunit of DNA gyrase and confers resistance to the antibiotic coumermycin A(1). The utility of the coumermycin-resistant gyrB(r) gene for targeted gene disruption is limited by a high frequency of recombination with the endogenous gyrB gene. A kanamycin resistance gene (kan) was introduced into B. burgdorferi, and its use as a selectable marker was explored in an effort to improve the genetic manipulation of this pathogen. B. burgdorferi transformants with the kan gene expressed from its native promoter were susceptible to kanamycin. In striking contrast, transformants with the kan gene expressed from either the B. burgdorferi flaB or flgB promoter were resistant to high levels of kanamycin. The kanamycin resistance marker allows efficient direct selection of mutants in B. burgdorferi and hence is a significant improvement in the ability to construct isogenic mutant strains in this pathogen.

Flutamide-hydroxypropy-beta-chiyclodextrin complex: formulation, physical characterization, and absorption studies using the Caco-2 in vitro model

PURPOSE

The objective of this research was to formulate flutamide (FLT) in hydroxypropyl-beta-cyclodextrin (HPbetaCyD), and to investigate FLT transcellular permeation from the complex using the Caco-2 monolayer in vitro model.

METHODS

Classical solubility data were used to derive thermodynamic parameters which, together with Differential Scanning Calorimetry (DSC), (1)H-NMR and (19)F-NMR, were used to characterize and derive stability constants for the FLT-HPbetaCyD complex. The Caco-2 cell line was used to examine the role of HPbetaCyD on the passage of FLT across cell monolayers in vitro.

RESULTS

The solubility of FLT in water (1.46 mmol/L) increased almost 170 times (to 243.45 mmol/L) in the presence of 50% (w/v) HPbetaCyD. Solubility data for FLT in aqueous HPbetaCyD were used to derive thermodynamic parameters (DeltaG degrees at 298 K = -3.48, DeltaH degrees = 2.85, DeltaS degrees at 298 K = 21.24). The solubility of FLT in HPbetaCyD increased proportionally with an increase in temperature. The FLT-HPbetaCyD complex had an A(L)-type (DSC) isotherm, consistent with a linear increase in FLT solubility and unchanged stoichiometry. The DSC of free FLT and HPbetaCyD showed endothermic peaks at 110 degrees C and 300 degrees C, respectively. FLT-HPbetaCyD did not display a free-FLT endothermic response, but exhibited broadening of the endothermic peak in the HPbetaCyD region. (19)F- and (1)H-NMR chemical shifts of FLT moved upfield as a function of its increased solubility in the presence of HPbetaCyD. The FLT-HPbetaCyD stability constant, K(s) (1:1) was estimated to be 356 M(-1 )and 357 M(-1), from thermodynamic and (19)F NMR data, respectively. The apical-to-basal permeability coefficient (P(eff) = 4.75 x 10(-5) cm.s(-1)) for FLT across Caco-2 cell monolayers at 37; C increased as HPbetaCyD concentrations were reduced, indicative of transepithelial passage via passive diffusion of available free FLT in solution. Studies in the presence and absence of Ca(2+ )ruled out a significant paracellular transport component.

CONCLUSIONS

FLT-HPbetaCyD is a relatively stable, 1:1 inclusion complex. Formation of this complex substantially increases the water solubility of FLT, but HPbetaCyD, except in high dilution, reduces transcellular passage of FLT in the Caco-2 cell in vitro model.

Borrelia burgdorferi B31 Erp proteins that are dominant immunoblot antigens of animals infected with isolate B31 are recognized by only a subset of human lyme disease patient sera

Sera from animals infected with Borrelia burgdorferi isolates yield intense immunoblot signals from the B31 ErpA/I/N and ErpB/J/O proteins, which have apparent molecular masses of 19 and 60 kDa, respectively. Since B. burgdorferi proteins with those molecular masses are of immunodiagnostic importance, Lyme disease patient sera were used in studies of B31 lysates and recombinant B31 ErpA/I/N and ErpB/J/O proteins. Immunoblot analyses indicated that only a minority of the patients produced antibodies that recognized the tested B31 Erp proteins. Southern blot analyses of Lyme disease spirochetes cultured from 16 of the patients indicated that all these bacteria contain genes related to the B31 erpA/I/N and erpB/J/O genes, although signal strengths indicated only weak similarities in many cases, suggestive of genetic variability of erp genes among these bacteria. These data indicate that Erp proteins are generally not the 19- and 60-kDa antigens observed on serodiagnostic immunoblots.

A bacterial genome in flux: the twelve linear and nine circular extrachromosomal DNAs in an infectious isolate of the Lyme disease spirochete Borrelia burgdorferi

We have determined that Borrelia burgdorferi strain B31 MI carries 21 extrachromosomal DNA elements, the largest number known for any bacterium. Among these are 12 linear and nine circular plasmids, whose sequences total 610 694 bp. We report here the nucleotide sequence of three linear and seven circular plasmids (comprising 290 546 bp) in this infectious isolate. This completes the genome sequencing project for this organism; its genome size is 1 521 419 bp (plus about 2000 bp of undetermined telomeric sequences). Analysis of the sequence implies that there has been extensive and sometimes rather recent DNA rearrangement among a number of the linear plasmids. Many of these events appear to have been mediated by recombinational processes that formed duplications. These many regions of similarity are reflected in the fact that most plasmid genes are members of one of the genome's 161 paralogous gene families; 107 of these gene families, which vary in size from two to 41 members, contain at least one plasmid gene. These rearrangements appear to have contributed to a surprisingly large number of apparently non-functional pseudogenes, a very unusual feature for a prokaryotic genome. The presence of these damaged genes suggests that some of the plasmids may be in a period of rapid evolution. The sequence predicts 535 plasmid genes >/=300 bp in length that may be intact and 167 apparently mutationally damaged and/or unexpressed genes (pseudogenes). The large majority, over 90%, of genes on these plasmids have no convincing similarity to genes outside Borrelia, suggesting that they perform specialized functions.

pSURF-2, a modified BAC vector for selective YAC cloning and functional analysis

A modified bacterial artificial chromosome (BAC) vector, pSURF-2, adapted for the selective subcloning of yeast artificial chromosome (YAC) sequences was constructed. DH10B-U, a pyrF derivative of the highly transformable E. coli strain DH10B was also constructed and used for the detection of Ura+ recombinants carrying DNA linked to YAC right arms. The vector's properties were illustrated in two main ways. (i) An intact 25-kb YAC containing a mouse tyrosinase minigene was cloned into pSURF-2. Appropriately spliced tyrosinase RNA was detected by reverse transcription (RT)-PCR in extracts of cells transiently lipofected with the cloned YAC. (ii) Cells expressing human cystic fibrosis transmembrane conductance regulator (CFTR) from an integrated pSURF-2 recombinant containing a cDNA expression cassette were selected using the hygromycin-resistance (HyTK) marker of the vector and characterized by RT-PCR and immunoprecipitation. The unique I-SceI site and HyTK marker of pSURF-2 are designed to facilitate subsequent functional studies of cloned DNA.

Stability of erp loci during Borrelia burgdorferi infection: recombination is not required for chronic infection of immunocompetent mice

Borrelia burgdorferi can persistently infect mammals despite their production of antibodies directed against bacterial proteins, including the Erp lipoproteins. We sequenced erp loci of bacteria reisolated from laboratory mice after 1 year of infection and found them to be identical to those of the inoculant bacteria. We conclude that recombination of erp genes is not essential for chronic mammalian infection.

Elimination of contaminant Escherichia coli chromosomal DNA from preparations of P1 artificial chromosome recombinants facilitates directed subcloning

The subcloning of large inserts (>50 kbp) from P1-derived artificial chromosomes (PACs) was found to be hindered by the presence of contaminating Escherichia coli chromosomal fragments which, because of their smaller median size, are recovered preferentially as unwanted subclones. A significant fraction of contaminating DNA was seen to persist after conventional plasmid purification methods. We describe a rigorous protocol for eliminating the bulk of contamination that involves plasmid isolation on commercially available silica-based columns followed by three pulsed field gel electrophoresis steps. Using this, we were able to subclone 55, 85 and 90 kbp PAC inserts but failed to subclone a 195 kbp PAC insert. After surveying a range of DNA purification methods, we devised an optimised protocol that allowed us to subclone the 195 kbp insert. The optimised protocol, which reliably yields DNA with essentially no contaminating material, consists of plasmid isolation on silica-based columns followed by treatment with highly purified DNaseI and retrieval by electroelution of restriction-digested DNA electrophoresed on a single pulsed field gel. By inference it is applicable to the purification of large inserts from other single-copy plasmid vectors such as bacterial artificial chromosomes (BACs).

Cold-regulated gene expression and freezing tolerance in an Arabidopsis thaliana mutant

Low temperature is an important environmental factor influencing plant growth and development. In this study, we report the characterization of a genetic locus, HOS2, which is defined by three Arabidopsis thaliana mutants. The hos2-1, hos2-2 and hos2-3 mutations result in enhanced expression of RD29A and other stress genes under low temperature treatment. Gene expression in response to osmotic stress or ABA is not affected in the hos2 mutants. Genetic analysis indicates that the hos2 mutations are recessive and in a nuclear gene. Compared with the wild-type plants, the hos2-1 mutant plants are less capable of developing freezing tolerance when treated with low non-freezing temperatures. However, the hos2-1 mutation does not impair the vernalization response. These results indicate that HOS2 is a negative regulator of low temperature signal transduction important for plant cold acclimation.

Genetic studies in Borrelia burgdorferi

Borrelia burgdorferi, the agent of Lyme disease, has recently joined a growing number of micro-organisms for which the entire genomic sequence is known. Despite this wealth of information, little is known about the contribution of specific spirochetal components to the pathogenesis of Lyme disease or their function in the normal life cycle of the organism. This discrepancy is due in part to the lack of a well-developed genetic system in B. burgdorferi, which in turn can be attributed to its relatively recent isolation and the dissimilarity of Borrelia from other genetically tractable bacteria. We are interested in several plasmid-encoded gene products in B. burgdorferi that may play a role in sensing and adaptation to the different environments the spirochete encounters as it completes an infectious cycle between the tick vector and the mammalian host. We are developing genetic tools with which to test the roles of specific B. burgdorferi gene products in the transmission cycle in an animal model of Lyme disease. We have demonstrated targeted gene inactivation by allelic exchange, using the gyrBr gene encoding coumermycin-resistant topoisomerase as a selectable marker. Spirochetes are transformed by electroporation and coumermycin-resistant colonies are screened by PCR for allelic exchange at the targeted locus. We have successfully inactivated several genes of interest in the type strain B31. We are investigating the utility of additional antibiotic resistance genes as selectable markers in B. burgdorferi. Targeted gene inactivation is a powerful tool with which to investigate the role of particular proteins in the basic biology and virulence of a pathogenic microorganism. We have made significant advances in our ability to genetically manipulate B. burgdorferi in order to address these issues. However, the available methods are incomplete and far from routine. We are currently improving existing methods as well as developing additional genetic tools with which to augment genetic studies in B. burgdorferi.

Falls risk factors in an acute-care setting: a retrospective study

Research findings have been contradictory regarding risk factors for falls in the acute-care setting. Identification of factors that place individuals at risk of falling in this setting are a priority because falls result in high morbidity and mortality and thus increased healthcare costs. The purpose of this study was to extend knowledge beyond the known risk factors of age and medical diagnosis by comparing the characteristics of 301 adults who fell while hospitalized with a matched sample of adults who did not fall while hospitalized. A descriptive, retrospective, comparative design was used. The fall and non-fall group were matched on age and primary medical diagnosis at the time of discharge. Data were collected from hospital incident reports and medical records. Logistic regression for matched groups identified 5 risk factors, as follows. Incontinence. The odds of falling were 11.3 (CI = 3.85, 33.05) times greater for those who were incontinent than for those who were not incontinent. Long hospital stay. The odds of falling were 9.9 (CI = 4.89, 19.88) times greater for those hospitalized 19 days or longer than for those hospitalized less than 19 days. Dependency for ambulation. The odds of falling were 6 (CI = 2.83, 12.84) times greater for those who were dependent for ambulation than for those who were independent. Independency for hygiene. The odds of falling were 2.5 (CI = 1.23, 4.88) times greater for those who were independent for hygiene than for those who were dependent. Lack of regular exercise. The odds of falling were twice as high (CI = 1.00, 3.82) for those who did not exercise regularly as for those who exercised regularly. These findings suggest that ongoing assessment may be more important than the admission assessment in identifying risk factors for falls in the acute-care setting. No 2 studies have found exactly the same set of risk factors, although some findings are consistent across studies. This suggests that those risk factors that are consistent across studies may identify persons who are at the greatest risk for falls and that other risk factors for falls are specific to a patient population.

Transformation of the Lyme disease spirochete Borrelia burgdorferi with heterologous DNA

Studies of the spirochete Borrelia burgdorferi have been hindered by the scarcity of genetic tools that can be used in these bacteria. For the first time, a method has been developed by which heterologous DNA (DNA without a naturally occurring B. burgdorferi homolog) can be introduced into and persistently maintained by B. burgdorferi. This technique uses integration of circular DNA into the bacterial genome via a single-crossover event. The ability to transform B. burgdorferi with heterologous DNA will now permit a wide range of experiments on the biology of these bacteria and their involvement in the many facets of Lyme disease.

HOS1, a genetic locus involved in cold-responsive gene expression in arabidopsis

Low-temperature stress induces the expression of a variety of genes in plants. However, the signal transduction pathway(s) that activates gene expression under cold stress is poorly understood. Mutants defective in cold signaling should facilitate molecular analysis of plant responses to low temperature and eventually lead to the identification and cloning of a cold stress receptor(s) and intracellular signaling components. In this study, we characterize a plant mutant affected in its response to low temperatures. The Arabidopsis hos1-1 mutation identified by luciferase imaging causes superinduction of cold-responsive genes, such as RD29A, COR47, COR15A, KIN1, and ADH. Although these genes are also induced by abscisic acid, high salt, or polyethylene glycol in addition to cold, the hos1-1 mutation only enhances their expression under cold stress. Genetic analysis revealed that hos1-1 is a single recessive mutation in a nuclear gene. Our studies using the firefly luciferase reporter gene under the control of the cold-responsive RD29A promoter have indicated that cold-responsive genes can be induced by temperatures as high as 19 degrees C in hos1-1 plants. In contrast, wild-type plants do not express the luciferase reporter at 10 degrees C or higher. Compared with the wild type, hos1-1 plants are l ess cold hardy. Nonetheless, after 2 days of cold acclimation, hos1-1 plants acquired the same degree of freezing tolerance as did the wild type. The hos1-1 plants flowered earlier than did the wild-type plants and appeared constitutively vernalized. Taken together, our findings show that the HOS1 locus is an important negative regulator of cold signal transduction in plant cells and that it plays critical roles in controlling gene expression under cold stress, freezing tolerance, and flowering time.

Humoral immunity to Borrelia burgdorferi N40 decorin binding proteins during infection of laboratory mice

A Borrelia burgdorferi N40 genomic expression library was screened with serum from actively infected mice to identify gene products that elicit protective immunity. A clone that contained a putative bicistronic operon containing two genes that encoded 20- and 22-kDa lipoproteins was identified and sequenced. These genes showed homology with the genes encoding decorin binding proteins DbpB and DbpA, respectively, of B. burgdorferi 297 and B31. N40-dbpA DNA hybridized with B. burgdorferi N40 DNA on a single 48-kb linear plasmid. Homologous genes could be amplified under various degrees of stringency by PCR or hybridized by Southern blotting from B. burgdorferi sensu stricto N40 and B31, and from B. burgdorferi sensu lato PBi and 25015, but not PKo. Recombinant N40-DbpB and N40-DbpA were reactive with antibody in serum from infected mice, and serum was more reactive against N40-DbpA than against B. burgdorferi N40 recombinant P39, OspC, or OspA. Sera from mice infected with B. burgdorferi sensu lato strains PKo and PBi were weakly reactive against N40-DbpB and N40-DbpA, and sera from mice infected with 25015 were moderately reactive, compared to sera from mice infected with B. burgdorferi N40. Hyperimmunization of mice with N40-DbpA, but not N40-DbpB, induced protective immunity against syringe challenge with cultured B. burgdorferi N40. DbpA may therefore be one of the antigens responsible for eliciting protective antibody known to exist in serum from infected mice. DNA amplification and serology suggest that DbpB and DbpA are likely to have homologs throughout the B. burgdorferi sensu lato family, but they are likely to be heterogeneous.

Borrelia burgdorferi erp proteins are immunogenic in mammals infected by tick bite, and their synthesis is inducible in cultured bacteria

Borrelia burgdorferi, the causative agent of Lyme disease, can contain multiple genes encoding different members of the Erp lipoprotein family. Some arthropod-borne bacteria increase the synthesis of proteins required for transmission or mammalian infection when cultures are shifted from cool, ambient air temperature to a warmer, blood temperature. We found that all of the erp genes known to be encoded by infectious isolate B31 were differentially expressed in culture after a change in temperature, with greater amounts of message being produced by bacteria shifted from 23 to 35 degrees C than in those maintained at 23 degrees C. Mice infected with B31 by tick bite produced antibodies that recognized each of the Erp proteins within 4 weeks of infection, suggesting that the Erp proteins are produced by the bacteria during the early stages of mammalian infection and may play roles in transmission from ticks to mammals. Several of the B31 Erp proteins were also recognized by antibodies from patients with Lyme disease and may prove to be useful antigens for diagnostic testing or as components of a protective vaccine.

Genetic analysis of osmotic and cold stress signal transduction in Arabidopsis: interactions and convergence of abscisic acid-dependent and abscisic acid-independent pathways

To dissect genetically the complex network of osmotic and cold stress signaling, we constructed lines of Arabidopsis plants displaying bioluminescence in response to low temperature, drought, salinity, and the phytohormone abscisic acid (ABA). This was achieved by introducing into Arabidopsis plants a chimeric gene construct consisting of the firefly luciferase coding sequence (LUC) under the control of the stress-responsive RD29A promoter. LUC activity in the transgenic plants, as assessed by using in vivo luminescence imaging, faithfully reports the expression of the endogenous RD29A gene. A large number of cos (for constitutive expression of osmotically responsive genes), los (for low expression of osmotically responsive genes), and hos (for high expression of osmotically responsive genes) mutants were identified by using a high-throughput luminescence imaging system. The los and hos mutants were grouped into 14 classes according to defects in their responses to one or a combination of stress and ABA signals. Based on the classes of mutants recovered, we propose a model for stress signaling in higher plants. Contrary to the current belief that ABA-dependent and ABA-independent stress signaling pathways act in a parallel manner, our data reveal that these pathways cross-talk and converge to activate stress gene expression.

Characterization of cp18, a naturally truncated member of the cp32 family of Borrelia burgdorferi plasmids

We have mapped the genes encoding the antigenic lipoproteins OspE and OspF to an approximately 18-kb circular plasmid in Borrelia burgdorferi N40. Sequencing and restriction mapping have revealed that this plasmid, cp18, is homologous to an 18-kb region of the cp32 circular plasmids found in the Lyme disease spirochetes. Our data show that cp18 may have arisen from an ancestral cp32 plasmid by deletion of a 14-kb region of DNA, indicating that a significant portion of the cp32 plasmid is not essential in cis for plasmid maintenance. These findings suggest that a relatively small recombinant plasmid capable of being stably maintained in B. burgdorferi could be constructed from a cp32 plasmid.

Central venous catheters in patients with AIDS

Central venous catheters (CVCs) for patients with AIDS are at risk of a number of complications including bacterial infections. A 6-year retrospective review was undertaken of the records of the 33 patients (42% infected by injection drug use (IDU)) who received intravenous therapy both in hospital and at home via CVCs. Twenty-eight per cent of 53 insertions suffered a complication, the commonest of which was a pneumothorax (8%). The post insertion complication rate was 0.98/100 catheter days (cd). Thrombotic occlusion (0.15/100 cd) was the commonest non septic event while sepsis was overall the commonest event (0.69/ 100 cd) of which half were considered serious (0.33/100 cd). The most frequently isolated organisms were Staphylococci spp. (71%). The median time to an exit site infection was 59 days and to serious catheter sepsis 86 days. Infection did not differ significantly with age, gender, transmission risk activity or catheter type although Portacaths had the lowest rate of infection (0.33/100 cd). The median survival of the 53 CVCs was 88 days although if the temporary catheters were excluded it was 118 days. Kaplan-Meier estimates of survival analysis revealed 55%, 32% and 19% of all the CVCs surviving 3, 6 and 12 months respectively. Our experience suggests that home intravenous therapy and previous IDU does not preclude the use of CVCs although further research is needed on reducing the infection-related complications of such therapy.

The Borrelia burgdorferi circular plasmid cp26: conservation of plasmid structure and targeted inactivation of the ospC gene

The 26 to 28kb circular plasmid of B. burgdorferi sensu lato (cp26) is ubiquitous among bacteria of this group and contains loci implicated in the mouse-tick transmission cycle. Restriction mapping and Southern hybridization indicated that the structure of cp26 is conserved among isolates from different origins and culture passage histories. The cp26 ospC gene encodes an outer surface protein whose synthesis within infected ticks increases when the ticks feed, and whose synthesis in culture increases after a temperature upshift. Previous studies of ospC coding sequences showed them to have stretches of sequence apparently derived from the ospC genes of distantly related isolates by homologous recombination after DNA transfer. We found conservation of the promoter regions of the ospC and guaA genes, which are divergently transcribed. We also demonstrated that the increase in OspC protein after a temperature upshift parallels increases in mRNA levels, as expected if regulatory regions adjoin the conserved sequences in the promoter regions. Finally, we used directed insertion to inactivate the ospC gene of a non-infectious isolate. This first example of directed gene inactivation in B. burgdorferi shows that the OspC protein is not required for stable maintenance of cp26 or growth in culture.

Homology throughout the multiple 32-kilobase circular plasmids present in Lyme disease spirochetes

We have characterized seven different 32-kb circular plasmids carried by Borrelia burgdorferi isolate B31. Restriction endonuclease recognition site mapping and partial sequencing of these plasmids indicated that all seven are probably closely related to each other throughout their lengths and have substantial relationships to cp8.3, an 8.3-kb circular plasmid of B. burgdorferi sensu lato isolate Ip21. With the addition of the seven 32-kb plasmids, this bacterial strain is known to carry at least 10 linear and 9 circular plasmids. Variant cultures of B. burgdorferi B31 lacking one or more of the 32-kb circular plasmids are viable and, at least in some cases, infectious. We have examined a number of different natural isolates of Lyme disease borreliae and found that all of the B. burgdorferi sensu stricto isolates and most of the B. burgdorferi sensu lato isolates tested appear to carry multiple 32-kb circular plasmids related to those of B. burgdorferi B31. The ubiquity of these plasmids suggests that they may be important in the natural life cycle of these organisms. They may be highly conjugative plasmids or prophage genomes, which could prove to be useful in genetically manipulating B. burgdorferi.

Directed insertion of a selectable marker into a circular plasmid of Borrelia burgdorferi

Studies of the biology of Borrelia burgdorferi and the pathogenesis of Lyme disease are severely limited by the current lack of genetic tools. As an initial step toward facile genetic manipulation of this pathogenic spirochete, we have investigated gene inactivation by allelic exchange using a mutated borrelial gyrB gene that confers resistance to the antibiotic coumermycin A1 as a selectable marker. We have transformed B. burgdorferi by electroporation with a linear fragment of DNA in which this selectable marker was flanked by sequences from a native borrelial 26-kb circular plasmid. We have identified coumermycin A1-resistant transformants in which gyrB had interrupted the targeted site on the 26-kb plasmid via homologous recombination with the flanking sequences. Antibiotic resistance conferred by the mutated gyrB gene on the plasmid is dominant, and transformed spirochetes carrying this plasmid do not contain any unaltered copies of the plasmid. Coumermycin A1 resistance can be transferred to naive B. burgdorferi by transformation with borrelial plasmid DNA from the initial transformants. This work represents the first example of a directed mutation in B. burgdorferi whereby a large segment of heterologous DNA (gyrB) has been inserted via homologous recombination with flanking sequences, thus demonstrating the feasibility of specific gene inactivation by allelic exchange.

A family of genes located on four separate 32-kilobase circular plasmids in Borrelia burgdorferi B31

We have identified four loci in Borrelia burgdorferi B31 that contain open reading frames capable of encoding six proteins that are related to the antigenic proteins OspE and OspF. We have designated these proteins Erp, for OspEF-related protein, and named their respective genes erp. The erpA and erpB genes are linked, as are erpC and erpD, and the pairs probably constitute two operons. The erpG and erpH genes appear to be monocistronic. The ErpA and ErpC proteins are expressed by B. burgdorferi B31 in culture and are recognized by a polyclonal antiserum raised against the OspE protein of B. burgdorferi N40. The four erp loci are each located on different 32-kb circular plasmids that contain additional DNA sequences that are homologous to each other and to an 8.3-kb circular plasmid of B. burgdorferi sensu lato Ip2l. All four 32-kb plasmids can be maintained within a single bacterium, which may provide a model for the study of plasmid replication and segregation in B. burgdorferi.

Temperature-related differential expression of antigens in the Lyme disease spirochete, Borrelia burgdorferi

Previous studies have demonstrated that Borrelia burgdorferi in the midguts of infected ticks shows increased expression of the antigenic outer surface protein OspC after the ticks have ingested a blood meal. This differential expression is at least partly due to a change in temperature, as an increase in OspC levels is also observed when cultures are shifted from 23 to 35 degrees C. Immunoblotting of bacterial lysates with sera from infected mice indicated that the levels of several additional antigens were also increased in bacterial cultures shifted to 35 degrees C; we have identified one antigen as OspE. We have also observed differential expression of OspF, which has been proposed to be coexpressed in an operon with the gene encoding OspE.

The preceptor experience: a qualitative study of perceptions of nurse preceptors regarding the preceptor role

This qualitative, exploratory, and descriptive survey was undertaken to identify benefits and disadvantages of the preceptor role as perceived by nurse preceptors. Information regarding rewards preceptors perceived as desirable also was obtained. Findings from this study can be used to develop preceptor programs that increase job satisfaction for preceptors and improve the learning environment for orientees.

Periodic acid-Schiff (PAS)-positive deposits in brain following kainic acid-induced seizures: relationships to fos induction, neuronal necrosis, reactive gliosis, and blood-brain barrier breakdown

Periodic acid-Schiff (PAS)-positive deposits have been demonstrated in the central nervous system (CNS) of patients suffering from a wide variety of neurodegenerative disorders including Alzheimer's disease, presenile dementia, Parkinson's disease, diabetes mellitus, myoclonic epilepsy, and cerebral palsy. The etiology of these deposits and their relationship to mechanisms of progressive neurodegeneration is unknown. In the present study, we demonstrate that the kainic acid model of limbic status epilepticus provides a useful system for the study of PAS-positive staining. The relationship between PAS-positive deposition, induction of fos-like immunoreactivity (FLI), neuronal necrosis, reactive gliosis, and blood-brain barrier breakdown following the kainic acid induction of status epilepticus was investigated. Epileptiform activity was elicited in rats by intraperitoneal administration of 10 mg/kg kainic acid and brains were examined 3, 5, 12, 24, 72, and 168 h after drug injection. Four distinct types of PAS-positive staining in rat brain were observed: type 1, extracellular matrix (ECM) or blood vessel associated-material; type 2, granular deposits; type 3, glial labelling; and type 4, neuronal labelling. Results demonstrated that the four types of PAS-positive staining were differentially associated with specific markers of neuropathology: (1) type 1 ECM staining and type 3 glia were preferentially localized to edematous tissue; (2) the majority of type 3 glia were identified as reactive astrocytes, while a minority of appeared to be proliferating microglia; (3) type 1 blood vessels labelled hemorrhaging vasculature; (4) early deposition of type 2 granules was predictive of subsequent cell loss; (5) chronic type 2 granular deposits and type 4 neuronal labelling not associated with cell death could be predicted by early changes in FLI; and (6) chronic deposition of all four forms of PAS-positive material was correlated with earlier, transient blood-brain barrier compromise. The results support the growing literature that local carbohydrate metabolism may be one of a constellation of parameters important to the development of progressive neurodegeneration.

Direct microdissection and microcloning of a translocation breakpoint region, t(1;11)(q42.2;q21), associated with schizophrenia

We describe the generation of large-fragment microclone libraries from the chromosomal breakpoint of a reciprocal balanced translocation linked to schizophrenia. The abnormality was visible under the phase-contrast microscope, allowing direct dissection from unstained, unbanded metaphases. Two separate microdissection experiments yielded 443 and 672 recombinants, respectively. Following complete EcoRI digestion, inserts with an average size of 0.3 kb (range, 0.2-3 kb) were obtained in the first experiment and 1.5 kb (range, 0.15-6.5 kb) in the second. FISH analysis of pooled clones "painted" back onto the derivative chromosome and assignment of microclones to somatic cell hybrids confirmed the fidelity of the method. Microdissection of chromosome regions identified by karyotype rearrangements in unstained, unbanded metaphases is a potentially powerful tool for positional cloning.

Expression and sequence of outer surface protein C among North American isolates of Borrelia burgdorferi

The expression of outer surface protein C (OspC) was determined for North American Borrelia burgdorferi isolates HB19, DN127cl9-2, 25015 and both low and high culture passage B31. A monoclonal antibody detected the presence of OspC protein in only two isolates, while polyclonal antiserum identified this protein in all five isolates. The ospC gene was cloned and sequenced for isolates HB19, DN127cl9-2 and 25015, and compared with the published ospC sequences of other Lyme disease spirochetes. Both the nucleotide and amino acid sequences were found to vary as much among isolates from the same geographic area as between isolates of different species.

Partial sequencing and mapping of clones from two maize cDNA libraries

As one component of a maize genome project, we report the analysis of a number of randomly selected cDNAs, by a combination of measuring mRNA expression, 'single-pass' sequencing (SPS), and genome mapping. Etiolated seedling (490) and membrane-free polysomal endosperm cDNA clones (576) were evaluated for their transcription levels by hybridizing with a probe prepared from total mRNA and categorized as corresponding to abundantly or rarely expressed mRNAs and as either constitutive or tissue-specific. A total 313 clones from the two libraries were submitted to 'single-pass' sequencing from the presumed 5' end of the mRNA and the nucleotide sequence compared with the GenBank database. About 61% of the clones showed no significant similarities within GenBank, 14% of the clones exhibited a high degree of similarity, while the remaining 25% exhibited a lesser degree of similarity. The chromosomal location of more than 300 clones was determined by RFLP mapping using standard populations. The results demonstrate that a combination of analyses provides synergistic information in eventually deducing the actual function of these types of clones.