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Biomedical subjects

D Ellis

Publications and source records attributed to D Ellis.

At least 19 recordsLinked to original sources
PubMed2007

The energetic consequence of specific dynamic action in southern bluefin tuna Thunnus maccoyii.

The effect of feeding on the rate of oxygen consumption (M(O2)) of four groups of three southern bluefin tuna Thunnus maccoyii (SBT) was examined in a large static respirometer at water temperatures of 18.2-20.3 degrees C. Six feeding events of rations between 2.1-8.5% body mass (%M(b)) of Australian sardines (Sardinops neopilchardus) were recorded (two of the groups were fed twice). Before feeding, fish swam between 0.71 and 1.4 body lengths s(-1) (BL s(-1)) and the routine metabolic rate (RMR) was 366+/-32.5 mg kg(-1) h(-1) (mean +/- s.e.m.). For all trials, M(O2) was elevated post feeding, presumably as a result of specific dynamic action (SDA). Swimming velocity was also elevated post feeding for periods similar to that of M(O2) (between 20-45 h, longest for the largest rations). Post feeding swimming velocity increased to between 0.87-2.6 BL s(-1) and was also dependent on ration consumed. It is suggested that the purpose of increased post-feeding swimming velocity was to increase ventilation volume as a response to the enhanced metabolic demand associated with SDA. Peak post-prandial M(O2) increased linearly with ration size to a maximum of 1290 mg kg(-1) h(-1), corresponding to 2.8 times the RMR. When converted to its energy equivalent, total magnitude of SDA was linearly correlated with ration size to a maximum of 192 kJ kg(-1) h(-1), and as a proportion of gross energy ingested (SDA coefficient), it averaged 35+/-2.2%. These results demonstrate that, although the factorial increase of SDA in SBT is similar to that of other fish species, the absolute energetic cost of SDA is much higher. These results support the contention that tuna are energy speculators, gambling high rates of energy expenditure for potentially higher rates of energy returns. The ration that southern bluefin tuna require to equal the combined metabolic costs of SDA and RMR is estimated in this study to be 3.5%M(b) of Australian sardines per day.

Animals↗
PubMed2006

Psychosocial factors and treatment adherence in paediatric HIV/AIDS.

A social ecological model provides a promising framework for understanding the individual, family, and societal factors contributing to non-adherence to treatment of paediatric HIV. This study explored which factors relevant to this model are associated with caregivers' adherence and child health outcomes. A cross-sectional design was utilized to assess relationships among current individual, familial, extra-familial factors, caregiver adherence, and viral load. Data were collected from 43 caregivers, and viral load data were obtained from the medical records of their HIV+ children. Caregiver drug and alcohol use and HIV+ status were associated with non-adherence and elevated viral load. Negative outcome expectancy was associated with lower adherence but was not significant in the multivariate analyses. Family factors were not significant, but these measures had low reliability in this sample. Extra-familial factors such as dissatisfaction with medical specialty care and more stressful life events were not directly associated with adherence but were related to increased caregiver substance use. Results of this first study to explore multiple predictors of adherence and health outcomes in paediatric HIV require replication with larger samples, but findings suggest caregiver characteristics that place children at risk for disease progression due to poor adherence to treatment.

Adolescent↗
PubMed2005

An assessment of the efficiency of fungal DNA extraction methods for maximizing the detection of medically important fungi using PCR.

To date, no single reported DNA extraction method is suitable for the efficient extraction of DNA from all fungal species. The efficiency of extraction is of particular importance in PCR-based medical diagnostic applications where the quantity of fungus in a tissue biopsy may be limited. We subjected 16 medically relevant fungi to physical, chemical and enzymatic cell wall disruption methods which constitutes the first step in extracting DNA. Examination by light microscopy showed that grinding with mortar and pestle was the most efficient means of disrupting the rigid fungal cell walls of hyphae and conidia. We then trialled several published DNA isolation protocols to ascertain the most efficient method of extraction. Optimal extraction was achieved by incorporating a lyticase and proteinase K enzymatic digestion step and adapting a DNA extraction procedure from a commercial kit (MO BIO) to generate high yields of high quality DNA from all 16 species. DNA quality was confirmed by the successful PCR amplification of the conserved region of the fungal 18S small-subunit rRNA multicopy gene.

Cell Wall↗
PubMed2004

Quality control limits for voriconazole disk susceptibility tests on Mueller-Hinton agar with glucose and methylene blue.

An international collaborative study was performed in order to propose quality control limits for voriconazole disk diffusion tests on Mueller-Hinton agar with 2% glucose and 0.5 micro g of methylene blue per ml. The supplement may be added to the agar before autoclaving, or Mueller-Hinton agar plates may be flooded with a glucose-methylene blue solution. Replicate tests on both types of agar plates with 1- micro g voriconazole disks generated data to propose zone size limits for tests of Candida parapsilosis ATCC 22019 (28 to 37 mm), Candida albicans ATCC 90028 (31 to 42 mm), and Candida krusei ATCC 6258 (16 to 25 mm). Candida tropicalis ATCC 750 was not useful for this purpose.

Agar↗
PubMed2003

Foot pump prophylaxis for deep venous thrombosis-rate of effective usage following knee and hip arthroplasty.

We recorded the usage of foot pumps during the post-operative period in 29 patients undergoing knee or hip arthroplasty and made 621 recordings. Effective utilisation of foot pumps was seen in 37.2% of cases. There was a gradual reduction in correct utilisation with each day that passed post-operatively (day 1, 60.4%; day 2, 48.8%; day 3, 28.8%; day 4, 21.4%; day 5, 23%). This gradual reduction was statistically significant ( P=0.001) and mainly occurred between the second and third post-operative days. Effective usage was 60.2% overall at night and 36.4% during the day. Our results question the efficiency of foot pumps in deep venous thrombosis prophylaxis in the context of a true clinical setting.

Analysis of Variance↗
PubMed2003

Evaluation of a commercial ELISA for detecting Norwalk-like virus antigen in faeces.

A commercially available enzyme immunoassay, the IDEIA Norwalk-like virus (NLV) enzyme linked immunosorbent assay (ELISA; Dako Cytomation, Ely, UK) for detecting NLV antigen in faecal samples and determining the NLV genogroup was evaluated. The performance of the ELISA was compared with that of electron microscopy and the reverse transcription polymerase chain reaction by testing a panel of faecal samples collected from patients involved in outbreaks of gastroenteritis. When compared with reverse transcription-polymerase chain reaction (RT-PCR), the ELISA had a sensitivity and specificity of 55.5 and 98.3%, respectively. This compares with a sensitivity and specificity for EM of 23.9 and 99.2%, respectively. The sensitivity and specificity of the ELISA for determining the aetiology of a Norwalk virus-like outbreak, based on two or more positive samples within an outbreak, were 52.2 and 100% when two samples were collected from an outbreak and 71.4 and 100% when six or more samples were collected. The ELISA correctly identified the NLV genogroups of viruses previously characterised by partial DNA sequencing. The ELISA is a suitable alternative to the preliminary screening by EM for investigating outbreaks of gastroenteritis. Outbreaks, negative by ELISA should be examined by RT-PCR in order to detect strains non-reactive in the assay and virus strains from representative ELISA positive outbreaks should be characterised fully to allow the genetic diversity of NLVs co-circulating in the population to be described.

Antigens, Viral↗
PubMed2003

Quality control limits for fluconazole disk susceptibility tests on Mueller-Hinton agar with glucose and methylene blue.

An international collaborative study was performed in order to propose quality control limits for fluconazole disk diffusion susceptibility tests on Mueller-Hinton agar with 2% glucose and 0.5 micro g of methylene blue per ml. The supplements may be added before autoclaving the agar, or Mueller-Hinton agar plates may be flooded with a glucose-methylene blue solution. Replicate tests on both types of agar plates generated data to propose zone size limits for tests of Candida parapsilosis ATCC 22019 (22 to 33 mm), C. tropicalis ATCC 750 (26 to 37 mm), and C. albicans ATCC 90028 (28 to 39 mm). C. krusei ATCC 6258 was not useful for this purpose.

Agar↗
PubMed2002

Characterization of virulence, colony morphotype and the glycopeptidolipid of Mycobacterium avium strain 104.

SETTING: Members of the Mycobacterium avium complex (MAC) are responsible for mycobacterial disease in children, the aged and in immunocompromised individuals. The complex consists of different species, serovars and morphologic forms that vary in virulence. One isolate of the MAC is currently being sequenced (MAC 104) and was chosen based on its derivation from an AIDS patient and the fact that it could be genetically manipulated. OBJECTIVE: MAC 104 was therefore analyzed for virulence, colony morphotype and expression of the glycopeptidolipid (GPL) responsible for serotying differences and the rough to smooth morphological switch. RESULTS: The isolate was found to be virulent in the murine model of low-dose aerosol infection in that it could colonize the lung, proliferate within the tissue and disseminate to other organs. MAC 104 expressed a variety of colony morphotypes, the most prevalent of which were smooth opaque, smooth transparent and rough. All three morphotypes could persist in the lung; however, the transparent and rough morphotypes grew more rapidlyinvivo. The rough morphotype was unusual in that it expressed an atypical form of the GPL usually absent from rough morphotypes. CONCLUSION: This characterization complements the genome data and confirms that MAC 104 behaves similarly to other MAC isolates.

Animals↗
PubMed2001

Crystal engineering with heteroboranes. I. 1-Carboxy-1,2-dicarba-closo-dodecaborane(11).

The title compound, C(3)H(12)B(10)O(2) or 1-COOH-1,2-closo-C(2)B(10)H(11), forms centrosymmetric dimers through intermolecular hydrogen bonding between the carboxylic acid groups, resulting in the formation of an eight-membered ring [R(2)(2)(8)]. The C==O bond of the carboxylic acid group almost eclipses the unsubstituted cage C atom, with a C-C-C-O torsion angle of 2.6 (2) degrees.

Journal Article↗
PubMed2001

Subsurface dimerization in III-V semiconductor (001) surfaces.

We present the atomic structure of the c(8 x 2) reconstructions of InSb-, InAs-, and GaAs-(001) surfaces as determined by surface x-ray diffraction using direct methods. Contrary to common belief, group III dimers are not prominent on the surface, instead subsurface dimerization of group III atoms takes place in the second bilayer, accompanied by a major rearrangement of the surface atoms above the dimers to form linear arrays. By varying the occupancies of four surface sites the (001)-c(8 x 2) reconstructions of III-V semiconductors can be described in a unified model.

Journal Article↗
PubMed2001

Sequence analysis of insecticidal genes from Xenorhabdus nematophilus PMFI296.

Three strains of Xenorhabdus nematophilus showed insecticidal activity when fed to Pieris brassicae (cabbage white butterfly) larvae. From one of these strains (X. nematophilus PMFI296) a cosmid genome library was prepared in Escherichia coli and screened for oral insecticidal activity. Two overlapping cosmid clones were shown to encode insecticidal proteins, which had activity when expressed in E. coli (50% lethal concentration [LC(50)] of 2 to 6 microg of total protein/g of diet). The complete sequence of one cosmid (cHRIM1) was obtained. On cHRIM1, five genes (xptA1, -A2, -B1, -C1, and -D1) showed homology with up to 49% identity to insecticidal toxins identified in Photorhabdus luminescens, and also a smaller gene (chi) showed homology to a putative chitinase gene (38% identity). Transposon mutagenesis of the cosmid insert indicated that the genes xptA2, xptD1, and chi were not important for the expression of insecticidal activity toward P. brassicae. One gene (xptA1) was found to be central for the expression of activity, and the genes xptB1 and xptC1 were needed for full activity. The location of these genes together on the chromosome and therefore present on a single cosmid insert probably accounted for the detection of insecticidal activity in this E. coli clone. Although multiple genes may be needed for full activity, E. coli cells expressing the xptA1 gene from the bacteriophage lambda P(L) promoter were shown to have insecticidal activity (LC(50) of 112 microg of total protein/g of diet). This is contrary to the toxin genes identified in P. luminescens, which were not insecticidal when expressed individually in E. coli. High-level gene expression and the use of a sensitive insect may have aided in the detection of insecticidal activity in the E. coli clone expressing xptA1. The location of these toxin genes and the chitinase gene and the presence of mobile elements (insertion sequence) and tRNA genes on cHRIM1 indicates that this region of DNA represents a pathogenicity island on the genome of X. nematophilus PMFI296.

Animals↗
PubMed2001

Pediatric solid-organ transplant recipients carry chronic loads of Epstein-Barr virus exclusively in the immunoglobulin D-negative B-cell compartment.

Solid-organ transplant recipients are at risk for development of lymphoproliferative diseases. The purpose of this study was to examine the distribution of Epstein-Barr virus (EBV) load in the peripheral blood of pediatric transplant recipients who had become chronic viral load carriers (>8 copies/10(5) lymphocytes for >2 months). A total of 19 patients with viral loads ranging from 20 to 5,000 viral genome copies/10(5) lymphocytes were studied. Ten patients had no previous diagnosis of posttransplant lymphoproliferative disease (PT-LPD), while nine had recovered from a diagnosed case of PT-LPD. No portion of the peripheral blood viral load was detected in the cell-free plasma fraction. Viral DNA was found in a population of cells characterized as CD19(hi) and immunoglobulin D negative, a phenotype that is consistent with the virus being carried exclusively in the memory B-cell compartment of the peripheral blood. There was no difference in the compartmentalization based upon either the level of the viral load or the past diagnosis of an episode of PT-LPD. These results have implications for the design of tests to detect EBV infection and for the interpretation and use of positive EBV PCR assays in the management of transplant recipients.

Adolescent↗
PubMed2000

Outcome after steroid withdrawal in pediatric renal transplant patients receiving tacrolimus-based immunosuppression.

BACKGROUND: Corticosteroids have always been an integral part of immunosuppressive regimens in renal transplantation. The primary goal of this analysis was to assess the safety of steroid withdrawal in our pediatric renal transplant recipients receiving tacrolimus-based immunosuppression. METHODS: Between December 1989 and December 1996, 82 renal transplantations were performed in pediatric patients receiving tacrolimus-based immunosuppression. Two of these patients lost their grafts within 3 weeks of transplantation (and were still on steroids at the time of graft loss), and were excluded from further analysis. Seventy-four patients (92.5%) were taken off prednisone a median of 5.7 months after transplantation. Of these 74, 56 (70%) remained off prednisone (OFF), and 18 (22.5%) were restarted on prednisone a median of 14.8 months after discontinuing steroids (OFF --> ON). 6(7.5%) were never taken off prednisone (ON). The mean follow-up was 59 +/- 23 months. RESULTS: The 1-, 3-, and 5-year actuarial patient survival rates in the OFF group were 100%, 98%, and 96%, respectively; in the OFF --> ON group, they were 100%, 100%, and 100%, and in the ON group, they were 100%, 83%, and 83%. The 1-, 3-, and 5- year actuarial graft survival rates in the OFF group were 100%, 95%, and 82%, respectively; in the OFF --> ON group, they were 100%, 89%, and 83%; and in the ON group, they were 100%, 50%, and 33%. Two of the six graft losses in the OFF group, three out of four in the OFF --> ON Group, and two out of five in the ON group, were to chronic rejection. A time-dependent Cox regression analysis showed that the hazard for graft failure for those who came and stayed off prednisone was 0.178 relative to those who were never withdrawn from prednisone (P=0.005). Patients who were 10 years of age or younger were withdrawn from prednisone earlier (median: 5 months) than those older than 10 years (median: 7.3 months, P=0.02). In addition, patients who never had acute rejection were withdrawn from steroids earlier (median: 5 months) than those who had one or more episodes of acute rejection (median: 7.6 months, P=0.001). There was no effect of donor age, race, sex, recipient race, sex, cadaveric versus living donor, 48-hr graft function, panel reactive antibody, and total HLA mismatches or matches on the likelihood of being weaned off steroids. Serum creatinine at most recent follow-up in the OFF group was 1.2 +/- 0.5 mg/dl; in the OFF --> ON group, it was 1.8 +/- 0.9 mg/dl, and in the ON group it was 2.0 mg/dl (P<0.003). The incidence of rejection in the OFF, OFF --> ON, and ON groups was 39%, 77%, and 100%, respectively (P<0.05). CONCLUSION: These data suggest that steroid withdrawal in pediatric renal transplant patients receiving tacrolimus-based immunosuppression is associated with reasonable short- and medium-term patient and graft survival, and acceptable renal function. Patients who discontinue and then resume steroids had patient and graft survival rates comparable with those in patients who discontinue and stay off steroids, but had a higher serum creatinine and a higher incidence of rejection.

Adolescent↗
PubMed2000

Epstein-Barr virus gene expression in the peripheral blood of transplant recipients with persistent circulating virus loads.

Pediatric solid organ transplant recipients are at risk for Epstein-Barr virus (EBV)-driven lymphoproliferative disease. The expression of 5 sentinel EBV genes (EBNA1, EBNA2a, LMP1, LMP2a, and ZEBRA) was examined in solid organ transplant recipients who developed persistent virus loads in their peripheral blood lymphocytes after transplantation. Two distinct groups were identified. LMP2a gene expression alone was detected among 12 of 14 patients carrying EBV loads < or =100 copies/10(5) lymphocytes. The other 2 low-load carriers made LMP2a RNA but also expressed LMP1 RNA. In contrast, LMP2a and LMP1 gene expression was detected among 11 of 13 patients carrying a virus load >100 copies/10(5) lymphocytes. Two high-load carriers made LMP1 RNA but not the RNA for LMP2a or any of the other viral genes. Therefore, persistent low-load carriers appear to maintain an apparently normal state of latent viral infection, whereas high-load carriers display a unique LMP1:LMP2a pattern of viral gene expression that has not been previously described.

Adolescent↗