Competence of urban rats as reservoir hosts for Lyme disease spirochetes

To determine whether urban rats serve efficiently as reservoir hosts for the agent of Lyme disease, we recorded the frequency of infection in nymphal Ixodes ricinus (L.) ticks that had fed as larvae on experimentally infected Norway rats, Rattus norvegicus (Berkenhout), or on black rats, R. rattus (L.), and evaluated the nidicolous venue of transmission. Subadult vector ticks attached readily to Norway rats as well as black rats and virtually all became infected in the course of feeding. Larval ticks detached when these nocturnally active hosts were at rest. Rats appeared to be competent reservoir hosts of Lyme disease spirochetes in a transmission cycle in urban sites.     

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.     

Ultrastructural characteristics of Lyme disease spirochetes (Borrelia burgdorferi) isolated from Ixodes persulcatus in China

Diluting composite materials with unfilled resin to facilitate clinical application during direct lamination will result in an alteration of filler loading with possible changes of physical properties. This study compared the surface hardness and abrasion resistance of a visible light-cured microfilled and hybrid resin with and without dilution. Samples were prepared, cured, and stored in distilled water at 37 degrees C for 24 hours before testing. Knoop hardness values were obtained from the upper surface of 10 samples in three dilution and control groups of each material. Three samples of the dilution and control groups were similarly prepared and stored for toothbrush abrasion testing. Data from the hardness and abrasion tests were subjected to analysis of variance and Tukey's test at a 0.05 level of significance. Results showed that dilution had a significant effect on surface hardness of the materials tested, although the diluted materials were not significantly different from the controls. Abrasion tests showed visible evidence of abrasion on all samples, but dilution showed no significant effect on abrasion resistance of the materials tested.     

Genospecies identification and characterization of Lyme disease spirochetes of genospecies Borrelia burgdorferi sensu lato isolated from rodents in Taiwan

Lyme disease spirochetes of the genospecies Borrelia burgdorferi sensu lato were identified and characterized for the first time in Taiwan. Seven isolates, designated TWKM1 to TWKM7, were purified from the ear tissues of three species of rodents captured from seven localities of Taiwan. The immunological characteristics of these Taiwan isolates were compared with those of other genospecies of Lyme disease spirochetes by analyzing the protein profiles and reactivities with B. burgdorferi-specific monoclonal antibodies (MAbs). The genospecies of these Taiwan isolates were also identified by the similarities in their plasmid profiles and differential reactivities with genospecies-specific PCR primers. Although two distinct protein profiles were observed among the seven Taiwan isolates, the MAb reactivities against the outer surface proteins of B. burgdorferi of all of these isolates were consistent with those of B. burgdorferi sensu lato. The similarities of the plasmid profiles also confirmed the identities of these Taiwan isolates. PCR analysis indicated that all of these Taiwan isolates were genetically related to the genospecies B. burgdorferi sensu stricto. These results demonstrate the first identification of Lyme disease spirochetes in Taiwan and also highlight the increasing demand for defining the reservoirs and vector ticks of B. burgdorferi. A serosurvey for Lyme disease infection in the human population of Taiwan may also be required.     

A shuttle vector system for studying ionizing radiation-induced mutagenesis in mammalian cells

In vivo application of red blood cells (RBC) modified with avidin-biotin complex has been suggested recently for various purposes. However, avidin attachment to RBC alters their biocompatibility. Thus, it has been described that avidin-carrying biotinylated RBC were lysed by the complement. In the present work interaction between avidin-carrying RBC and nucleated cells has been examined. It was found that attachment of avidin, but not streptavidin, to RBC led to binding of avidin-carrying RBC to nucleated cells. Adhesiveness of nucleated cells for avidin-carrying RBC varied for different types of nucleated cells. The strongest adhesion was observed with human fibroblasts and rat Kupffer cells, while rat liver endothelial cells were practically non-adhesive for avidin-carrying RBC of corresponding species. In contrast with avidin (streptavidin)-induced lysis by the complement, avidin-induced adhesion was independent of temperature, the presence of divalent ions and mode of avidin attachment. Polyanions (dextran sulphate and heparin) efficiently inhibited the adhesion presumably due to interaction with the membrane-bound avidin. Polyanions to a much lesser extent inhibited lysis of avidin-carrying RBC, which might be a result of their interaction with the complement components. Polycations also blocked adhesion of avidin-carrying RBC to nucleated cells, presumably due to interaction with negatively charged cell-surface components. Therefore, attachment of avidin to RBC alters their biocompatibility, due to both high positive charge of avidin and the cross-linking of biotinylated membrane proteins.     

An animal behavior model for studying the actions of LSD and related hallucinogens

Cats injected with LSD (d-lysergic acid diethylamide) exhibit a group of behaviors that appear to be specific to hallucinogenic drugs. Two of these behaviors, limb flick and abortive grooming, have an extremely low frequency of occurrence in normal cats, but often dominate the behavior of LSD-treated cats. The frequency of occurrence of this group of behaviors is related to the dose of LSD. The behavioral changes are long-lasting following a single injection of LSD, and exhibit tolerance following the repeated administration of LSD. They are not elicited by a variety of control drugs, but are elicited by other indole nucleus hallucinogens. Because the behavioral effects are specific, reliable, easy to score, and quantifiable, they represent an animal model that can be used in studies of the effects of LSD and related hallucinogens.     

A new animal model for maxillary sinus floor augmentation: evaluation parameters

Stress mediators, CRF-41 and vasopressin known to be synthesized in, and released from the parvocellular neurosecretory neurons of the hypothalamic paraventricular nucleus (PVN) are essential to release adrenocorticotropin (ACTH) in response to stress. In addition, suckling-induced prolactin (PRL) release also depends on the integrity of the PVN. In the present study, ether stress-induced adrenocorticotrop hormone (ACTH) and prolactin (PRL) release was studied 2, 5 and 42 days after placing lesions in the hypothalamic paraventricular nucleus (PVN) of male rats. Ether-induced ACTH secretion was strongly inhibited 2 and 5 days after lesions whereas 6 weeks later the lesion induced inhibition was fading. In contrast, PVN lesion failed to inhibit ether-induced PRL release at any time studied. The results suggest that contrary to previous suggestions the peptidergic neurons essential for stress-induced PRL release are outside the PVN.     

Prospects for a vaccine to prevent Lyme disease in humans

Vaccination with recombinant outer-surface protein A (OspA) preparations has been highly successful in protecting laboratory animals against challenge by strains of Borrelia burgdorferi closely related to the one from which the OspA was derived. Humoral immunity is sufficient for protection. Against natural infection introduced by ticks, the vaccine-induced immune response may begin to take effect in the tick itself--i.e., before the spirochete enters the host--and may extend to a broader spectrum of strains of B. burgdorferi than are represented in the vaccine. Single recombinant OspA vaccine preparations are currently being evaluated in two large-scale efficacy trials in adults in the United States. Greater heterogeneity among B. burgdorferi strains in Europe than among those in the United States will likely necessitate the development of a vaccine containing antigens from multiple strains; a multivalent vaccine may or may not be needed in the United States.     

Treponema denticola as a model for polar adhesion and cytopathogenicity of spirochetes

Recent studies suggest that the tip-oriented adhesion of Treponema denticola is a consequence of polar clustering of its adhesins on contact with the substratum and is compatible with viability. Such adhesion to cells stimulates a host of cytoskeletal and volume regulatory changes. These studies may give insight into mechanisms of colonization and cytopathogenicity of other pathogenic spirochetes.     

Ticks, Lyme disease spirochetes, trypanosomes, and antibody to encephalitis viruses in wild birds from coastal Georgia and South Carolina

Ticks and blood samples were collected from wild birds mist-netted on St. Catherine's Island, Georgia, and at the Wedge Plantation in coastal South Carolina in 1994 and 1995. Immature stages of 5 species of ixodid ticks were recovered from 10 of 148 (7%) birds belonging to 6 species in Georgia, whereas 6 ixodid species were recovered from 45 of 259 (17%) birds representing 10 avian species in South Carolina. Borrelia burgdorferi sensu lato was isolated from 27 of 120 (23%) screened ticks (Ixodes scapularis and Ixodes minor) recovered from South Carolina birds, but from none of 16 screened ticks removed from Georgia birds. This spirochete was also isolated from 1 of 97 (1%) birds in South Carolina. In 1995, neither eastern equine encephalitis (EEE) virus nor St. Louis encephalitis (SLE) virus was isolated from any of 218 bird sera screened, but serum neutralizing antibodies were found to EEE virus in 4 of 121 (3%) sera and to SLE virus in 2 of 121 (2%) sera from South Carolina. No antibody to either virus was detected in 51 avian sera screened from Georgia. Trypanosomes (probably Trypanosoma avium) were isolated from 1 of 51 (2%) birds from Georgia and from 13 of 97 (13%) birds from South Carolina. Our data suggest that some wild birds may be reservoir hosts for the Lyme disease spirochete and for encephalitis viruses in coastal Georgia and South Carolina and that migrating birds can disperse immature ticks infected with B. burgdorferi.     

A new spontaneous animal model of NIDDM without obesity in the musk shrew

The EDS (early-onset diabetes in suncus) colony has been developed as a new closed breeding colony of the musk shrew (Suncus murinus, Insectivora) exhibiting a high incidence of spontaneous diabetes mellitus. We investigated the characteristic features of diabetic shrews in this colony. All diabetic shrews are characterized by glycosuria (Tes-tape value > or = 3+), hyperglycemia (23.3 +/- 0.8 mmol/l) and polyuria, and they were affected by the age of 3 months. Cumulative incidence (64.1% in males and 27.8% in females) was kept intact after the age of 3 months. The growth pattern of diabetic shrews was similar to that of non-diabetic shrews, and obesity was not consistent in diabetic shrews. The intraperioneal glucose tolerance test revealed both impaired glucose tolerance and impaired insulin secretion in diabetic shrews. Insulin sensitivity of diabetic shrews decreased in the intraperioneal insulin tolerance test. Neither severe hypertrophy nor lymphocytic infiltration was observed in pancreatic islets of diabetic shrews. These facts suggested that diabetic shrews in the EDS colony should be classified as early-onset non-insulin dependent diabetes mellitus (NIDDM) without obesity. Early-onset of severe hyperglycemia with impaired glucose tolerance is a distinctive character compared with other non-obese NIDDM models in rodents. We concluded that the diabetic shrews in the EDS colony are a new animal model of human NIDDM without obesity.     

Arabidopsis as a model host for studying plant-pathogen interactions

Because the molecular biology and genetics of Arabidopsis thaliana are so well defined, it is potentially a superb subject for research on plant-pathogen interactions. Viruses, bacteria and fungi that infect Arabidopsis and are representative pathogens of economically important plants have recently been described. The search now is for a pathogenic fungus with tractable genetics to combine with a direct analysis of plant resistance genes.     

Recommendation to include OspA and OspB in the new immunoblotting criteria for serodiagnosis of Lyme disease

In October 1994, the Second National Conference on the Serologic Diagnosis of Lyme Disease recommended a two-step approach to serological testing. The first step was the performance of an enzyme-linked immunosorbent assay (ELISA); the second step was a confirmatory immunoblot. New criteria for the interpretation of a positive immunoblot were also recommended. The committee decided to omit the 31- and 34-kDa bands (OspA and OspB, respectively) from the choice of bands considered diagnostic for a positive immunoblot. Since we had previously included these in our diagnostic criteria for Lyme disease-positive immunoblots, we reviewed data for all patients attending a Lyme disease center with positive ELISAs and immunoblot assays for Lyme disease from 1 September 1992 to 31 December 1993. The criteria for a positive Western blot (immunoblot) were the presence of 5 or 12 bands, including the 10 recommended by the conference, and the presence of the 31- and 34-kDa protein bands. Of the 136 patients evaluated, 50 were considered to have Lyme disease. Of these 50, 4 (8%) would not have met immunoblot criteria for the diagnosis if the new recommendations were used. Had the 31- and 34-kDa bands been included as part of the diagnostic requirements for immunoblot, these patients would have been included. Although overdiagnosis of Lyme disease appears to be the more frequent problem, our concern is that the exclusion of the 31- and 34-kDa protein bands from the diagnostic criteria may result in the underdiagnosis of Lyme disease by those who would rely too heavily on serological confirmation. The addition of the 31- and 34-kDa bands to those recommended for confirmatory immunoblot should be reconsidered.     

Searching for Lyme disease in Colombia: a preliminary study on the vector

Since ageing is accompanied by various alterations of the immune system, the aim of the present study was to investigate the effect of age on the expression of surface markers in peripheral blood monocytes. We studied 28 healthy young subjects and 28 elderly subjects fulfilling the criteria of the SENIEUR protocol. Peripheral blood mononuclear cells were isolated and the expression of various surface markers was analysed by double colour flow cytometry. The mean fluorescence intensity of the intercellular adhesion molecule- (CD54), CD29, CD45RO and CD32 was increased significantly in CD14+ cells of elderly people when compared with the young subjects. No significant differences were found in the expression of CD11a, CD11b, CD15, CD26, CD27, CD33, CD45RA, CD45RB, CD49d, HLA-DR and CD65. In summary, we demonstrated significant increase in four monocyte surface markers in subjects of old age; this finding may be related to certain immune phenomena observed in ageing subjects such as auto-immunity.     

Bacterial pathogenesis: a variation on variation in Lyme disease

The discovery of antigenic variation in Borrelia burgdorferi, the bacterium that causes Lyme disease, provides a potential explanation for the chronic nature of infection as well as new insights into the genetic structure of highly recombinogenic loci responsible for combinatorial genetic diversification.