Biomedical subjects

K Vickery

Publications and source records attributed to K Vickery.

68 records · Page 4Linked to original sources

PubMed1996

Evaluation of image quality using 1 : 1 pitch and 1.5 : 1 pitch helical CT in children: a comparative study.

OBJECTIVE: The objective of this study was to compare the quality of 1 : 1 and 1.5 : 1 pitch helical contrast-enhanced thoracic and abdominal CT images in children who cannot cooperate for breath holding. MATERIALS AND METHODS: This is a retrospective study of 33 contrast-enhanced CT examinations in 11 children of 0-4 years of age. All children had an initial CT study using 1 : 1 pitch helical scanning followed over the next 6-36 months by one to four CT examinations with 1.5 : 1 pitch. Radiation dose with the two techniques was measured with a pencil ionization chamber. RESULTS: The two techniques provided comparable overall image quality. There was 33 % less radiation dose with 1.5 : 1 pitch helical scanning. CONCLUSION: The 1.5 : 1 pitch helical CT provides comparable quality images and a smaller radiation dose than 1 : 1 pitch in examining children aged 0-4 years.

Child↗

PubMed1996

DHBV manipulation and prediction of the outcome of infection.

BACKGROUND/AIMS: The immunological response of ducks to acute infection with duck hepatitis B virus (DHBV) has not been fully characterised. In this study the relationship between viral dose and the outcome of infection in immune competent 26-day-old ducks was examined. METHODS: Indirect ELISA assays were developed to detect the presence of antibody to DHB surface antigen and DHB core antigen. A DHBV serum pool was titrated in 1-day-old and 26-day-old ducklings. RESULTS: The ID50 dose of the ducks injected at 26 days of age was found to be 1000 times that of the ducks injected on day of hatch. The antibody responses and serum DHBV DNA were followed in eight ducks inoculated with DHBV positive serum when 26 days of gene and in three ducks infected with DHBV on day of hatch. The three ducks infected on day of hatch were viraemic by day 7 and remained highly viraemic throughout the experimental period. In the older ducks, inoculation with 1000ID50 resulted in the development of chronic carriage, while inoculation with either 100 or 10ID50 doses resulted in acute infection with or without viraemia. These ducks were able to clear the infection from their circulation, but only 50% cleared DHBV from the liver within the experimental period. All infected ducks developed anti-core activity. Only non-viraemic ducks developed anti-surface activity. CONCLUSION: DHBV infection can be established in immune competent adolescent ducks, with variable disease outcomes comparable to HBV infection in humans.

Acute Disease↗

PubMed1996

Establishment of an in-use testing method for evaluating disinfection of surgical instruments using the duck hepatitis B model.

Nosocomial transmission of hepatitis B virus (HBV), associated with interventional procedures, has been attributed to its survival on improperly decontaminated instruments. To date, guidelines for chemical disinfection of potentially contaminated heat-sensitive instruments have been based largely on extrapolation of data from in-vitro disinfectant testing. Direct infectivity testing has not been possible for HBV because of the lack of a practical culture assay or susceptible experimental animal model. In this study the related duck hepadnavirus was used to simulate in-vivo transmission of a HBV during surgery, and to evaluate the effectiveness of 2% glutaraldehyde disinfection of surgical laparoscopes. Multiple laparoscopic liver biopsies were performed on 'biohazardous' duck hepatitis B (DHBV) positive ducks. Laparoscopes were then subjected to different disinfection regimes using 2% glutaraldehyde, and residual infectivity tested by placing their tips into the peritoneal cavities of uninfected four-day-old ducklings. Direct transmission of DHBV occurred in all ducks when laparoscopes were not washed. Rinsing with water lowered the transmission rate to 64% and no infection transmission occurred after 5 min of contact time with the disinfectant. In contrast, previous in-vitro studies had shown complete viral inactivation after a shorter period of disinfection. It is postulated that the longer inactivation time observed in our study may be a result of surface interactions of virus and instrument, interfering with disinfectant access or activity. Tests of instrument surface samples for viral DNA by the polymerase chain reaction (PCR) did not correlate with transmission of virus infection in vivo. PCR is an inappropriate test for evaluating the efficacy of disinfectant action despite its sensitivity. This in use method will allow testing of other decontamination procedures and their effectiveness on more complex surgical instruments.

Animals↗

PubMed1996

2',3'-dideoxy-3'-fluoroguanosine inhibits duck hepatitis B virus in vivo.

Duck hepatitis B virus (DHBV) belongs to the same virus family as the human hepatitis B virus (HBV). Domestic ducks infected with DHBV can be used as an animal model for chronic hepatitis B virus infection in therapeutic trials. In this study the antiviral effect of the guanosine analogue 2',3'-dideoxy-3'-fluoroguanosine (FLG) was tried in vivo on chronically DHBV-infected ducks. The ducks were either congenitally infected, or inoculated with DHBV immediately post-hatch. FLG was given as intraperitoneal injections twice daily, at different dosages. Serum DHBV levels were determined by DNA dot-blot hybridization. A strong inhibition of serum DHBV DNA was observed with FLG doses down to 1 mg kg-1 day-1, given for 7 to 10 days. With the corresponding thymidine analogue, 2',3'-dideoxy-3'-fluorothymidine; however, no inhibition was obtained. This difference may be due to different phosphorylation mechanisms. Independently of FLG dose, serum DHBV DNA returned to pretreatment levels within a few days after cessation of therapy. After a long-term trial (FLG, 5 mg kg-1 day-1 for 33 days), the same relapse of DHBV production was seen. Thus, FLG is an efficient inhibitor of DHBV replication, and is a candidate for treatment of HBV infections. However, the effect is transient, and therefore combination with other types of anti-HBV drugs should be considered.

Animals↗

PubMed1995

In vitro response to mitogens by duck splenic mononuclear cells.

This study has defined the effects of cell concentration, culture conditions and mitogen concentration on the uptake of 3H-labelled thymidine by mononuclear cells (SMC) purified from the spleens of ducks. The mitogen stimulation of cultures containing from 5 x 10(2) to 2 x 10(6) cells per well or more took up 3H-thymidine without the need for mitogenic stimulation. The response to each mitogen tested--phytohaemagglutinin (PHA), concanavalin A (ConA) and lipopolysaccharide (LPS)--was distinctive, with between duck variation in the time for peak stimulation, the level of stimulation with PHA, the response to ConA was variable and the response to LPS was poor. Supplementation of the media with 20 per cent fetal calf serum instead of autologous duck serum was satisfactory.

Animals↗

PubMed1993

Preparation, characterization, cytotoxicity, and mutagenicity of a pair of enantiomeric platinum(II) complexes with the potential to bind enantioselectively to DNA.

The synthesis of a pair of enantiomeric Pt(II) complexes, [Pt(R,R-eap)Cl2] and [Pt(S,S-eap)Cl2] (eap = N,N-diethyl-2,4-pentanediamine), designed to bind enantioselectively to GpG and ApG sequences of DNA is described. The in vitro cytotoxicity of each of the enantiomers toward murine leukemia and human bladder tumor cells has been measured. The R,R enantiomer was found to be more active in the leukemia cells, but the difference was not as great as expected (IC50; R,R 14 microM, S,S 33 microM). In the bladder tumor cell line, no significant difference in activity was found. The two enantiomers had similar mutagenicity in the Salmonella reversion assay, but the R,R enantiomer was more cytotoxic in the bacterial cells. A structural analysis of the R,R enantiomer revealed that the ligand adopted an unexpected configuration, and a strain energy minimization analysis showed that this was a consequence of interactions between the diamine ligand and the dichloro ligands. The significance of the structural preferences with respect to the lower than expected enantiospecificity is discussed. Crystals of [Pt(R,R-eap)Cl2] are monoclinic; space group, P2(1)2(1)2(1); a = 7.909(5), b = 12.972(9), and c = 13.269(12) A; Z = 4; and the structure was refined to R = 0.025 (1657F).

Animals↗

PubMed1992

Effects of Phyllanthus plant extracts on duck hepatitis B virus in vitro and in vivo.

The effects of extracts of five Australian Phyllanthus species (P. hirtellus, P. gunnii, P. gasstroemii, P. similis and P. tenellus), other plant extracts and the antiviral drug foscarnet on duck hepatitis B virus (DHBV) endogenous DNA polymerase (DNAp) activity were compared. All 5 Phyllanthus species caused 50% inhibition at concentrations of dry weight between 350-800 micrograms/ml, which is comparable with the effect described for P. amarus on the DNAp of human and woodchuck hepatitis B viruses. Incubation of P. hirtellus with 100 ID50 DHBV neutralized infection. However, neither P. gasstroemi extract, given by intraperitoneal injection (i.p.) at a dose of 20 mg/kg 3 times per week to ducklings early in the incubation period, or P. hirtellus extract, given to established DHBV carrier ducklings, prevented or eliminated infection.

Animals↗

PubMed1991

Duck hepatitis B virus: a model to assess efficacy of disinfectants against hepadnavirus infectivity.

The efficacy of three proprietary glutaraldehyde disinfectants and their component bases was assessed using the duck hepatitis B virus (DHBV) model. Inactivation of infectivity of undiluted serum containing 10(6.8) ID50/ml DHBV was assessed after a mixture with an equal volume of disinfectant had stood at room temperature for 10 min. A dried spill of infectious serum was simulated using sterile filter paper disks, saturated with serum containing DHBV, dried and then exposed to test disinfectant for 10 min. Residual infectivity, and hence the reduction in virus titre, was determined by inoculation of dilutions of the treated samples into 1-day-old ducklings. A greater than 3 log10 reduction in virus titre could be demonstrated for the disinfectants as well as for some of their component bases. Disinfectant activity varied according to the method of viral presentation but a reduction of exposure time from 10 to 2.5 min did not diminish activity. The experimental protocol permits a comparative and quantitative assessment of the efficacy of both established and new disinfectants.

Animals↗

PubMed1990

Postexposure treatment of experimental DHBV infection: a new therapeutic strategy.

The therapeutic efficacy of antiviral agents for postexposure prophylaxis to hepadnavirus infection has been studied using acyclovir and foscarnet in the duck hepatitis B virus (DHBV) model. A total of 112 Pekin-Aylesbury ducks were inoculated with DHBV at 11 days post-hatch. Three days later, groups of these birds were injected intraperitoneally twice daily for 10 days with acyclovir (25 mg/kg) or foscarnet (250 mg/kg) or phosphate-buffered saline. Serum samples were taken before, during, and up to 4 weeks post-treatment and were analysed for DHBV DNA by dot hybridization. Liver tissue obtained at sacrifice was examined for viral DNA and for histological changes. At completion of treatment with acyclovir, 21 of 22 ducks were not viremic, compared with 6 of 26 control birds (P less than 0.001). Four weeks after withdrawal of acyclovir, 12 of 20 ducks remained nonviremic, compared with 2 of 23 controls (P less than 0.01). In liver tissue, viral DNA was detected in 10 of 19 treated ducks, compared with 21/24 controls (P less than 0.01). Histological changes of hepatitis were present in more of the control birds than in the treated group. The results with foscarnet treatment were similar, although a smaller inoculum of DHBV was used and fewer control birds became infected. The administration of antiviral agents soon after exposure prevented productive infection in approximately 50% of birds. Therefore, the use of a safe antiviral agent such as acyclovir, which can be given orally, should be considered in post-exposure prophylaxis against human hepatitis B virus (HBV) infection.

Acyclovir↗

PubMed1989

Immunity in Pekin ducks experimentally and naturally infected with duck hepatitis B virus.

The immune response to duck hepatitis B virus (DHBV) had not been elucidated. An assay was therefore established to detect the presence of antibody to DHB surface antigen (anti-DHBs) in serum of experimentally inoculated and naturally infected ducks. Anti-DHBs in serum was detected by indirect RIA from the percentage inhibition of binding of rabbit anti-DHBs to purified DHBsAg. Specificity was confirmed by positive and negative controls, infected and noninfected sera, and a mouse monoclonal antibody to DHB core antigen (anti-DHBc). Serum and liver samples were tested for DHBV DNA by dot-blot hybridization assay. Adult ducks repeatedly inoculated with DHBV remained non-viraemic but developed anti-DHBs. This antibody activity neutralized the infectivity of DHBV, which was experimentally inoculated into 1-day-old ducklings. In naturally infected flocks anti-DHBs was detected in a proportion of noninfected adult ducks as well as 1-day-old hatchlings. Anti-DHBs activity in hatchlings neutralized the infectivity of experimentally inoculated DHBV. Pekin ducks can therefore mount a neutralizing antibody response to DHBV, and immunity may be transferred in ovo from dam to off-spring.

Aging↗

PubMed1979