Roaming of dogs in remote Indigenous communities in northern Australia and potential interaction between community and wild dogs.

OBJECTIVE: To investigate the roaming of Indigenous community dogs and potential interaction with wild dogs and dingoes. DESIGN: Cross-sectional survey and longitudinal follow-up study. METHODS: Six remote Indigenous communities in Cape York Peninsula and Arnhem Land in northern Australia were selected. Hair samples were collected from community dogs and microsatellite DNA analyses were used to determine hybrid (>10% dingo DNA) status. Dogs were fitted with GPS collars and home range (ha) was estimated during monitoring periods of up to 3 days. RESULTS: In Cape York Peninsula, 6% of the 35 dogs sampled were dingo hybrids, whereas in Arnhem Land 41% of the 29 dogs sampled were hybrids. The median extended home range was estimated to be 4.54 ha (interquartile range, 3.40 - 7.71). Seven community dogs were identified with an estimated home range > 20 ha and home ranges included the bushland surrounding communities. No significant difference in home ranges was detected between hybrid and non-hybrid dogs. CONCLUSIONS: Study results provide some evidence (dingo hybridisation, bushland forays) of the potential interaction between domestic and wild dogs in northern Australia. The nature of this interaction needs further investigation to determine its role in disease transmission; for example, in the case of a rabies incursion in this region.

What influences the home range size of free-roaming domestic dogs?

In many regions of the world domestic dogs are free roaming and live in close relationship with humans. These free-roaming domestic dogs (FRDD) can cause public health problems such as dog bites and transmission of infectious diseases. To effectively control diseases transmitted by FRDD, knowledge on the dogs' behaviour is required. To identify predictors of home range (HR) size, we collected global positioning system data from 135 FRDD living in eight Aboriginal and Torres Strait Islander communities in Northern Australia. The core HR size ranged from 0·17 to 2·33 ha and the extended HR size from 0·86 to 40·46 ha. Using a linear mixed effect model with a Restricted Maximum Likelihood approach, the dog's sex and reproductive status were identified as predictors of roaming. Non-castrated males had the largest HRs, followed by neutered females. Also, FRDDs were found to roam further during the pre- than the post-wet season. These findings have implications for infectious disease spread. Identification of risk groups for disease spread within a population allows for more targeted disease response and surveillance. Further investigation of predictors of roaming in other FRDD populations worldwide would increase the external validity of such studies.

TGF-beta inhibits proliferation of and promotes differentiation of human promonocytic leukemia cells.

Transforming growth factor-beta 1 (TGF-beta 1) has been implicated in a variety of responses associated with wound healing and inflammation. Thus, TGF-beta 1 enhances production of several extracellular matrix proteins both in vitro and in vivo, is chemotactic for monocytes, and alters the functioning of lymphocytes. We have examined the ability of TGF-beta 1 to affect the behavior of human THP-1 promonocytic leukemia cells, a cell line with the capacity to differentiate into macrophage-like cells. TGF-beta 1 reduces the growth rate of these cells, induces morphologic changes, and promotes adherence to culture surfaces. In addition, the adherent cell population expresses high levels of esterase activity, acquires the ability to ingest latex beads, and releases elevated levels of interleukin 1. TGF-beta 1-treated cells also express elevated levels of the beta 2 family of integrins. Taken together, these results suggest that TGF-beta 1 is capable of promoting the maturation of promonocytic cells into macrophages. This outcome has implications at wound sites where TGF-beta 1 and a myriad of other factors interact with many cell types to facilitate healing.

Signal transduction events in chicken interleukin-1 production.

The HD11 chicken macrophage cell line was studied for growth characteristics using different culture media, serum concentrations, and incubation temperatures. Growth curves at 37 C revealed that the cells grew best in RPMI 1640 medium supplemented with 10% colostrum-free bovine serum (CFBS). Growth was not supported by RPMI 1640 medium supplemented with the serum replacement Nu Serum nor by PC-1 culture medium alone. However, coating culture plates with either chicken serum or Nu Serum enhanced HD11 cell growth in the PC-1 medium. Growth at 40 C was equivalent to that obtained at 37 C when RPMI 1640 medium with 10% CFBS or PC-1 medium in plates coated with chicken serum were used. Several stimuli were tested for their ability to induce interleukin-1 (IL-1) in HD11 macrophages under serum-free conditions. Lipopolysaccharide (2.5 micrograms/mL) or silica (50 micrograms/mL), increased extracellular IL-1 significantly after a 24-h treatment. In contrast, a superinduction protocol using phorbol 12-myristate 13-acetate, cycloheximide, butyrate, and actinomycin D did not increase extracellular IL-1 significantly. All three stimulants significantly elevated intracellular IL-1 after treatment. Protein kinase C inhibitors (H7 and retinal) as well as calmodulin-dependent kinase inhibitors (W7 and TFP) significantly diminished IL-1 production in the intracellular and extracellular compartments. Elevated cyclic adenosine 5'-monophosphate (cAMP) actuated by dibutyryl cAMP also increased IL-1 significantly. The dat indicate that both protein kinase C and calmodulin-dependent kinase mechanisms are important in signal transduction leading to IL-1 production.