Wolbachia infection and expression of cytoplasmic incompatibility in Armigeres subalbatus (Diptera: Culicidae)

Polymerase chain reaction screening revealed that Armigeres subalbatus (Coquillett), a vector of filariasis, was infected with the intracellular bacteria Wolbachia. Laboratory crosses between infected males and uninfected females resulted in less than half the number of offspring than control crosses between uninfected individuals when young (2- to 3-d-old) males were used in the cross. However, incompatibility was lost when old (14- to 17-d-old) males were used. Field-collected females did not show detectable cytoplasmic incompatibility, and this may be because of the age at which males mate in the field. We used head pigment fluorescence levels to age field males collected from mating swarms, and found that 25-63% of swarming males were older than 13 d. Male age may be one factor influencing the observed low levels of cytoplasmic incompatibility detected in the field.

A stable triple Wolbachia infection in Drosophila with nearly additive incompatibility effects

Drosophila simulans strains infected with three different Wolbachia strains were generated by experimental injection of a third symbiont into a naturally double-infected strain. This transfer led to a substantial increase in total Wolbachia density in the host strain. Each of the three symbionts was stably transmitted in the presence of the other two. Triple-infected males were incompatible with double-infected females. No evidence was obtained for interference between modification effects of the different Wolbachia strains in males. Some incompatibility was observed between triple-infected males and females. However, this incompatibility reaction is not a specific property of triple-infected flies, because it was also observed in double-infected strains.

Integrating infection control into the dental curriculum

The dental profession has possessed traditional standards of cross-infection control but the recent expression of real concerns by both the public and the profession over the transmissibility of infectious diseases in the dental surgery has demanded a formalized and extended approach to teaching cross-infection control in the dental curriculum. Clear curriculum content must be formulated within contemporary Workplace Health and Safety Guidelines and the Strategic Plan of the Dental School or academic health centre. The full integration demands that the area is taught as a discrete entity but recognized as an intrinsic part of each clinical encounter. This paper discusses the structure and integration of cross-infection control into the curriculum at the University of Queensland Dental School.

Modelling fungal growth on surfaces

Fungal growth in time and space at the substrate surface was modelled for a simple system mimicking solid-state fermentation, using a polycarbonate Nucleopore membrane laid over a glucose solution. Biomass production depends on both tip density and the diffusion of glucose within the fungal hyphae. The model predicts early increases in both height and concentration, followed by a period in which the biomass profile moves with a constant wavefront. The rate of increase in height increases as tip diffusivity increases or as the Monod saturation constant for glucose decreases.

Sources of information about HIV/AIDS and perceived risk of infection among heterosexual young adults: 1989 and 1994

This paper reports a study of sources of information about HIV/AIDS and trust of the sources among heterosexuals in 1989 (113 females and 91 males) and 1994 (185 females and 66 males). We also examined whether perceived personal risk of HIV infection was predicted by sources of information about HIV/AIDS, trust of the sources, how informed about AIDS people believed they were, and perceived risk of infection to others, as well as whether there was a relationship between perceived personal risk and safe sex behaviour Participants received most of their information about AIDS/HIV from magazines, newspapers, and television, but placed most trust on sources such as doctors and HIV/AIDS organisations. Perceived personal risk was influenced most by perceived risk to friends and to people with the same sexual practices. In the 1994 sample, perceived personal risk was correlated with the amount of condom use among participants with sexual experience. These results indicate ther has been. relative stability across a five-year period. They also point to the continuing discrepancy among young heterosexuals between the most-used and most-trusted sources of information, as well as to the importance of peer influence on perceptions of personal risk of HIV infection.

Infection of the epaulette shark, Hemiscyllium ocellatum (Bonnaterre), by the nematode parasite Proleptus australis Bayliss (Spirurida : Physalopteridae)

Seventy-two epaulette sharks, Hemiscyllium ocellatum (Bonnaterre), were infected with the nematode parasite Proleptus australis Bayliss, 1933. The parasite population was overdispersed. Infection intensity ranged from 3 to 1002 worms per fish stomach, and there was a positive correlation between shark length and number of parasites present. The majority of worms were attached to the stomach wall, and scanning electron microscopy and histological examination showed that worms penetrated the stomach lining. Worms were observed within the lamina propria of the stomach and occasionally penetrated the muscularis mucosa. Little to no inflammatory or cellular immune reaction to the presence of the parasites was observed, except in one case where a worm was being degraded by a host tissue response. There was a large amount of connective tissue proliferation as a result of nematode attachment,, but no obvious effects on the overall health of the sharks were seen. Three sharks were also found to be infected by the cestode Callitetrarhynchus sp.

Complement-mediated regulation of Trichomonas vaginalis infection in mice

Trichomonas vaginalis is a flagellated protozoan which causes trichomoniasis, a sexually transmitted disease of the human genitourinary tract, The importance of the alternative complement pathway in host defence against T. vaginalis was investigated in vitro. Kinetic studies utilising immunofixation following electrophoresis showed that both a strongly and weakly virulent strain of T, vaginalis activated murine serum C3. In vivo studies with congenic-resistant, C5-deficient, B10.D2/OSn- and C5-sufficient, B10.D2/nSn mice showed that the presence of C5 is a significant factor in the innate host resistance to primary infection with a strongly virulent, but not a weakly virulent trichomonad strain.

Both CD4(+) and CD8(+) lymphocytes reduce the severity of tissue lesions in murine systemic candidiasis, and CD4(+) cells also demonstrate strain-specific immunopathological effects

The role of T lymphocytes in host responses to sublethal systemic infection with Candida albicans was evaluated by mAb depletion of CD4(+) and CD8(+) cells from BALB/c and CBA/CaH mice, which develop mild and severe tissue damage, respectively. Depletion of CD4(+) lymphocytes from BALB/c mice markedly increased tissue damage, but did not alter the course of infection. In CBA/CaH mice, depletion of CD4+ cells abrogated tissue destruction in both brain and kidney at day 4 after infection, and significantly decreased fungal colonization in the brain. However, the severity of tissue lesions increased relative to controls from day 8 onwards. A small increase in tissue damage was evident in both mouse strains after depletion of CD8(+) cells. There were no major differences between days 4 end 8 after infection in cDNA cytokine profiles of CD4(+) lymphocytes from either BALB/c or CBA/CaH mice. After passive transfer into infected syngeneic recipients, spleen cells from infected CBA/CaH mice markedly increased tissue damage when compared to controls, and also caused a significant increase in fungal colonization in the brain. A similar transfer in BALB/c mice increased the number of inflammatory cells in and around the lesions, but had no effect on the fungal burden in brain and kidney. The data demonstrate that both CD4(+) and CD8(+) lymphocytes contribute to the reduction of tissue damage after systemic infection with C. albicans, and that the development and expression of CD4(+) lymphocyte effector function is influenced by the genetic background of the mouse.

HIV infection among women admitted to the gynaecology service of a district hospital in South Africa

Our objective was to determine the prevalence of HIV infection and disease-specific HIV prevalence among women admitted to the gynaecology service of a district hospital in South Africa over a 3-month period in 1997. This was done with the goal of developing HIV education and counselling services in this setting. HIV status was determined among 196 (96%) of 205 consecutive admissions; 82 (42%) tested HIV positive. The HIV-infected women were younger than the HIV uninfected women (mean age 27 vs 33 years, P=0.001). The disease-specific HIV prevalence was greater than or equal to 40% among women who had had abortions, pelvic inflammatory disease, or ectopic pregnancy. The length of hospital stay (mean 5.4 days) and mortality (1%) were similar in the 2 groups. Inpatient gynaecology services may be act important setting in Africa, within which to provide HIV education, counselling and care.

Insect peptides with improved protease-resistance protect mice against bacterial infection

At a time of the emergence of drug-resistant bacterial strains, the development of antimicrobial compounds with novel mechanisms of action is of considerable interest. Perhaps the most promising among these is a family of antibacterial peptides originally isolated from insects. These were shown to act in a stereospecific manner on an as-yet unidentified target bacterial protein. One of these peptides, drosocin, is inactive in vivo due to the rapid decomposition in mammalian sera. However, another family member, pyrrhocoricin, is significantly more stable, has increased in vitro efficacy against Gram-negative bacterial strains, and if administered alone, as we show here, is devoid of in vitro or in vivo toxicity. At low doses, pyrrhocoricin protected mice against Escherichia call infection, but at a higher dose augmented the infection of compromised animals. Analogs of pyrrhocoricin were, therefore, synthesized to further improve protease resistance and reduce toxicity. A linear derivative containing unnatural amino acids at both termini showed high potency and lack of toxicity in vivo and an expanded cyclic analog displayed broad activity spectrum in vitro. The bioactive conformation of native pyrrhocoricin was determined by nuclear magnetic resonance spectroscopy, and similar to drosocin, reverse turns were identified as pharmacologically important elements at the termini, bridged by an extended peptide domain. Knowledge of the primary and secondary structural requirements for in vivo activity of these peptides allows the design of novel antibacterial drug leads.

Cell death and immunohistochemistry of p53, c-Fos and c-Jun after spermine infection into the rat striatum

Administration of polyamines into the central nervous system results in tissue damage, possibly through the excitotoxic actions of the NMDA receptor. Direct injection of 100 nmol of spermine into the rat striatum produced a lesion equivalent to approximately 50% of the striatum. Analysis of the DNA in this region revealed the distinct ladder-like pattern of degradation often associated with apoptosis. This DNA fragmentation was confirmed in vivo using terminal deoxynucleotidyl-transferase-mediated biotinylated deoxyuridine triphosphate nick end labelling (TUNEL). The morphology of the TUNEL-positive cells showed marked differences at the needle tract when compared with cells in damaged areas away from the needle tract, suggesting a differential mechanism of cell death in these two regions. The patterns of p53, c-Fos and c-Jun protein expression were determined using immunohistochemistry. The number of p53-immunoreactive cells increased up to 14 h and returned to basal levels by 24 h. c-Fos protein expression transiently increased, peaking at 8 h after injection, c-Jun exhibited a protracted pattern of expression, remaining elevated up to 24 h. p53 protein expression was colocalised with TUNEL staining in areas away from the needle tract, but not in cells at the needle tract, suggesting once again a differential mechanism of cell death. At 14 h, c-Fos and c-Jun were not colocalised with TUNEL staining, suggesting that they are either not involved with the cell death process or that the time course of protein expression and the onset of DNA fragmentation do not overlap. This work represents the first characterisation of processes associated with cell death induced by spermine in vivo.

Osmolarity effects on observed insect cell size after baculovirus infection are avoided using growth medium for sample dilution

Rates of cell size increase are an important measure of success during the baculovirus infection process. Batch and fed batch cultures sustain large fluctuations in osmolarity that can affect the measured cell volume if this parameter is not considered during the sizing protocol. Where osmolarity differences between the sizing diluent and the culture broth exist, biased measurements of size are obtained as a result of the cell osmometer response. Spodoptera frugiperda (Sf9) cells are highly sensitive to volume change when subjected to a change in osmolarity. Use of the modified protocol with culture supernatants for sample dilution prior to sizing removed the observed error during measurement.