Biomedical subjects
Publications and source records attributed to R B Davey.
We present a case of fat necrosis in the thigh of a ten year old girl, resulting in unusual multiple, ovoid filling defects seen in the residual cavity following drainage of a subcutaneous haematoma. No similar cases have been found on review of the literature. The appearance is described to aid diagnosis at the time of initial cavity drainage, avoiding the need for further investigation.
Myositis ossificans is a benign, localized, ossifying lesion of soft tissues that is rarely reported in young children. This paper describes two cases found in a search of the surgical biopsy files of the Adelaide Children's Hospital over the 30 yr period from 1962 to 1991, in boys both aged 7 yrs. Diagnosis was assisted by combined clinical, radiological and histopathological information (including an adequate well-orientated biopsy in Case 1 that demonstrated the characteristic growth pattern) enabling differentiation from other possibilities such as fibrodysplasia ossificans progressiva.
When Boophilus microplus and Type-II hybrids (B. microplus females X B. annulatus males) were released simultaneously onto bovine hosts, mating between the two forms appeared not to be at random. There were more contypic and fewer intertypic matings than predicted under an assumption of panmixia. An examination of the patterns of matings revealed that more of the matings on the first two days of detachment were between the two sexes of B. microplus. Engorged females dropping on the last four days of maximum female detachment were predominantly hybrids mated to both B. microplus and hybrid males. The non-random mating pattern does not appear to be caused by assortative mating between B. microplus and Type-II hybrids, but because the B. microplus were competent to mate two days before the hybrids and the B. microplus males compete for males of both types better than the Type-II males.
The survival period for larvae of Boophilus annulatus (Say), Boophilus microplus (Canestrini) and hybridized Boophilus ticks was determined by exposure to various combinations of temperature (20, 25, 30 and 35 degrees C) and relative humidity (32, 63, 75, 84 and 97% RH) in the laboratory. Results indicated that within a given temperature and RH regime, there was no difference (P greater than 0.05) in larval survival among the three species tested, indicating that these ticks respond similarly over a wide range of temperature and RH combinations. Larval survival in all three species was longest (P less than 0.05) at 20 degrees C and either 84 or 97% RH. With each increase in temperature at the 84 and 97% RH treatment levels, there was a corresponding significant (P less than 0.05) decrease in larval survival. When the temperature reached 35 degrees C at all humidities or when the RH was 63% or less at all temperatures, the mean larval survival period was 43 days or less in all cases and little difference (P greater than 0.05) was observed among the treatment regimes included. Results suggest that at a RH of 75% and more, the temperature is the determining factor in larval survival, whereas at a RH of 63% and less the RH is the determining factor in larval survival, regardless of temperature.
With the introduction of silicone gel in 1981, the emphasis in the treatment of burn scar management has changed from pressure to the use of contact media. A range of 'contact media' has been introduced, allowing for therapy to be individualized to the patient and the scar. Over the last few years, the introduction of 'the adhesive technique' has allowed for earlier therapy with the aim of preventing or minimizing scar hypertrophy with better short- and long-term cosmetic results. The mode of action of 'contact media' is discussed, with a suggested hypothesis and further lines of investigation.
Eleven children received patient-controlled analgesia (PCA) for the management of severe burn pain, their ages ranged from 4.75 to 14 years. Periods of PCA ranged from 2 to 131 days. Three patients developed evidence of tolerance as shown by high dose requirements, but the patients weaned themselves rapidly when pain levels fell. We conclude that PCA provides good quality analgesia to school-age children requiring debridement and grafting for burns. Its use simplified one major aspect of the management of these children.
A comprehensive computer model was developed for simulation of the population dynamics of the cattle ticks, Boophilus microplus (Canestrini) and B. annulatus (Say). The model is deterministic and based on a dynamic life table with weekly time steps. The model simulates the effects of major environmental variables, such as ambient temperature, saturation deficit, precipitation, type of pasture, type of cattle, and cattle density on Boophilus cattle tick population dynamics. General validity of the model is established by comparing simulated and observed yearly densities of standard female ticks/host/day. B. microplus population comparisons were made for a series of years using weekly weather data from two locations in Queensland, Australia. The model also produced acceptable values for initial population growth rate, generation time, and 3-yr population density when historical weather at 7 locations in Australia and 23 locations in the Americas were used. This model provides a framework for the study of Babesia transmission by Boophilus ticks, and can be used to study the effects of control technologies and to develop more efficient and environmentally acceptable eradication strategies for Boophilus ticks.
The competitiveness of hybridized Boophilus males, which are 100% sterile, was compared to B. microplus (Canestrini). Hybrid larvae used in the study were the offspring derived by cross-mating B. annulatus (Say) males with B. microplus females. Cattle were infested with a total of 2,500 larvae at ratios of 5:1 and 10:1 (hybrid to pure strain). The reduction in egg hatch resulting from the hybrid males was 68 and 77.5% at the 5:1 and 10:1 ratios, respectively. Both treatment ratios produced egg sterility that were lower than expected, assuming purely random mating, suggesting that hybrid ticks were not as competitive as B. microplus males. At the 5:1 treatment level, genotypic determinations based on isoenzyme analysis indicated that mate pairings involving hybrid males occurred 20-40% less frequently than expected, whereas matings involving pure-strain B. microplus males occurred twice as frequently as expected. At the 10:1 treatment level, mate pairings involving hybrid males occurred 10-20% less frequently than expected, whereas pairings involving pure strain B. microplus occurred 2-4 times more frequently than expected. The results indicated that in a sterile hybrid male program, it would be necessary to increase the ratios of hybrids by approximately 2-fold over the 5:1 or 10:1 ratios to achieve the 80-90% sterility expected, because of the decreased competitiveness of hybrid males.
Explore the source record for details and available documents.
Cattle ticks, Boophilus annulatus (Say), previously reared only on cattle, were placed on 3 white-tailed deer, Odocoileus virginianus L. Ticks were maintained through successive generations solely on the same deer as they aged (3, 6, and 9 mo of age) and received repeated challenges (0, 1, and 2 previous challenges). Cattle were infested simultaneously to assess tick viability and provide a comparison of tick numbers, female weight, egg mass weight, and egg hatch. The initial infestation (3,000 larvae/animal) produced a mean of 12.7 and 506.7 females from deer and cattle, respectively. Ticks recovered from deer weighed less, laid smaller egg masses, and had lower egg hatchability than cattle-reared ticks. A second infestation (3,000 larvae/animal) produced a 6.3-fold reduction in tick numbers on deer (means = 2.0 females/deer), whereas the number on cattle increased (means = 578.0 females/calf). Ticks reared on the deer were again smaller, laid fewer eggs, and had lower egg hatch, although differences were not significant. A third infestation of deer (1,900 larvae/deer) produced only 1 engorged female tick and no viable eggs, thus eliminating the population of deer-reared ticks within 3 generations. Results of the study suggest that a population of B. annulatus will not be sustained indefinitely through time solely on deer; thus, efforts to reduce deer populations severely as a means of eradicating ticks are unnecessary.
Ovicidal activity of coumaphos, diazinon, dioxathion, chlorpyrifos, and crotoxyphos applied topically at 0.125, 0.25, and 0.5% (AI) to 1-d-old, 10-d-old, and 20-d-old eggs of southern cattle tick, Boophilus microplus (Canestrini), was determined. All acaricides produced some disruption of hatching of eggs in all age classes. Coumaphos, diazinon, dioxathion, and chlorpyrifos were most effective in reducing egg hatch of 1-d-old eggs but had little effect against 10- or 20-d-old eggs. Although crotoxyphos was comparable with other acaricides in reducing hatch in 1-d-old eggs, it caused significantly greater mortality (greater than or equal to 94.6%) in 20-d-old eggs than other compounds tested. Crotoxyphos applied at 0.5% (AI) is the only acaricide tested that provided sufficient ovicidal activity in all three egg age classes (greater than or equal to 85% reduction of hatch).
A study was done at the USDA-ARS, Cattle Fever Tick Research Laboratory, Mission, Tex., to determine the efficacy of a 50% wettable powder (WP) amitraz formulation applied as a whole-body spray in a standard dip vat, and in a laboratory bioassay against Boophilus annulatus (Say) on cattle. A study also was done at the King Ranch in Kleberg County, Tex., to determine the stability of 50% WP amitraz in a dip vat under South Texas conditions Cattle were infested with all parasitic life stages of B. annulatus and were sprayed or dipped with a concentration of 0.025% amitraz. As determined by calculations of the index of reproduction, the whole-body spray treatment provided 86% control of the ticks and the dip treatment provided 99.8% control. Laboratory bioassay results compared favorably with those obtained with the dip vat treatment. Amitraz WP settled very rapidly in the freshly charged ranch vat. However, as more cattle were dipped and the vat became polluted with dirt and excrement, settling occurred much more slowly. Overall, amitraz remained stable in the vat during the test period.
White-tailed deer (Odocoileus virginianus L.) were evaluated as an alternate host for the cattle fever tick, Boophilus annulatus (Say). The total of adult female ticks recovered and associated reproductive parameters were compared between deer and bovine hosts. Significantly fewer ticks were recovered from deer than from cattle; this was attributed to the grooming behavior of the deer. The mean weight of ticks taken from deer (243.5 mg) was significantly less than that of ticks recovered from cattle (344.5 mg) with about 15% of the ticks from deer prematurely detached. Egg mass weight from the ticks recovered from deer (129.4 mg) was significantly less than that of ticks from cattle (172.1 mg). A significant difference was observed between the percentage hatch of the eggs of ticks from deer (63.1%) and ticks from cattle (76.7%). The index of reproduction was about 20 times greater for the ticks from the cattle than for the ticks from the deer. When the larval progeny of the ticks recovered from deer were reared on cattle, significantly fewer adult females were recovered than when larvae of ticks recovered from cattle were reared on cattle. This indicates a possible reduction in viability. All other parameters were comparable between the two groups. Thus, deer are biologically suitable hosts for B. annulatus, but significantly fewer ticks complete engorgement and those that complete engorgement have reduced fecundity.
The effects of prolonged exposure at 12 degrees C on oviposition were determined for Boophilus microplus (Canestrini) females. The percentage of females ovipositing remained high (greater than or equal to 80%) for exposure times of less than or equal to 30 d, but declined to 0.0 and 6.7% when females were held for 90 and 105 d, respectively. Duration had no effect on the preoviposition period after females were returned to optimum temperature (25 degrees C). The number of eggs laid per female declined at each exposure interval between 15 d, where no significant adverse effect on egg deposition was noted, and 90 d, where no eggs were laid. The hatch of eggs derived from exposed females showed a similar decline as the exposure time increased. A strong negative relationship between exposure time and egg viability was observed for eggs deposited at optimum temperature and then exposed to low temperature at intervals of 0 to 105 d. Larval longevity also showed a substantial negative relationship to exposure time. Results of the investigation and differences noted to results with B. annulatus (Say) also are discussed.
A new technique for split skin graft fixation using 'Hypafix' adhesive dressing is described. Ninety-three patients with burns involving less than 20% body surface area grafted at the Adelaide Children's Hospital during February 1985-May 1987 were reviewed. Comparisons were made between the results of standard fixation and Hypafix methods. The Hypafix technique showed itself to be simple and reliable, affording considerable versatility and allowing early mobilization without splintage or sedation. The adhesive is readily loosened with Ungvita ointment allowing the dressing to be removed painlessly. In this study its use has shortened both the length of inpatient stay and outpatient follow-up in the Scar Management Programme.
The effect of temperature on the ovipositional biology of Boophilus annulatus (Say) was determined under laboratory conditions. Engorged females subjected to constant temperatures of 12 and 45 degrees C died without ovipositing, while females held at 15 and 40 degrees C laid eggs which did not hatch. The preoviposition period at 25-40 degrees C was 2-3 days; however, significant increases occurred at 20 degrees C (5.2 days) and at 15 degrees C (16.3 days). The number of eggs laid per female was ca. 2700 at temperatures of 25-35 degrees C, but decreased significantly at 20 degrees C (ca. 2300 eggs/female), 15 degrees C (ca. 1800 eggs/female), and at 40 degrees C (ca. 300 eggs/female). No differences were observed in the Conversion Efficiency Index (CEI) values at temperatures of 20-30 degrees C (ca. 50%), while temperatures of 15 and 40 degrees C produced the lowest CEI values at 35.6 and 4.9%, respectively. Hatch-ability of eggs was ca. 80% at temperatures of 20-35 degrees C. Incubation period of eggs ranged from 52.2 days at 20 degrees C to 16.2 days at 35 degrees C. The thermal threshold for egg development determined by linear regression was 12.9 degrees C. Females subjected to four fluctuating temperature regimens produced no differences in number of eggs/female (ca. 2400), CEI (ca. 50%), or hatchability of eggs (ca. 75%). Preoviposition period and incubation were significantly affected by a change in the thermoperiod, becoming longer in duration as the temperatures were decreased. From studying females exposed for various intervals from 0 to 105 days at 12 degrees C, indications were that the longer the exposure period the more adverse the effects were on oviposition and egg-hatch. Correspondingly, exposure of eggs to a temperature of 15 degrees C for up to 105 days gave indications that the longer the eggs remained at 15 degrees C, the lower the hatch would be after transfer back to a temperature of 25 degrees C.
Explore the source record for details and available documents.
Explore the source record for details and available documents.