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J O'Callaghan

Publications and source records attributed to J O'Callaghan.

At least 19 recordsLinked to original sources
PubMed2003

A polyketide synthase gene required for ochratoxin A biosynthesis in Aspergillus ochraceus.

Ochratoxin A is an important nephrotoxic and nephrocarcinogenic mycotoxin, produced by Aspergillus ochraceus as a polyketide-derived secondary metabolite. A portion of a putative polyketide synthase gene (pks) involved in the biosynthesis of this mycotoxin was cloned by using a suppression subtractive hybridization PCR-based approach. The predicted amino acid sequence of the 1.4 kb clone shared 28-35 % identity to acyl transferase regions from fungal polyketide synthases found in the databases. Based on reverse transcription PCR studies, the pks gene is expressed only under ochratoxin A permissive conditions and only during the early stages of the mycotoxin synthesis. A mutant in which the pks gene has been interrupted cannot synthesize ochratoxin A. This report is the first of the cloning and characterization of a gene involved in ochratoxin A biosynthesis.

Amino Acid Sequence↗
PubMed2002

Optimisation of the expression of a Trametes versicolor laccase gene in Pichia pastoris.

A cDNA encoding a laccase enzyme was isolated from a Trametes versicolor cDNA library. The gene was subcloned into the Pichia pastoris expression vector pPIC3.5 and transformed into the P. pastoris strains KM71 and GS115. Laccase-secreting transformants were selected by their ability to oxidise the substrate ABTS. No difference in laccase activity was observed between culture supernatants from GS115 (proteolytic) and KM71 (nonproteolytic) strains. The presence of at least 200 microM copper was necessary for optimal laccase activity in the culture supernatants. During growth of P. pastoris on minimal medium the pH of the medium was reduced to <3.0. If alanine was added to the medium the pH reduction was not as pronounced and at alanine concentrations >0.6% w/v the pH was kept constant for >7 days. Cultures in which the pH was maintained by alanine metabolism produced higher levels of laccase activity than those grown in the absence of alanine. This study describes the development of a medium that allows convenient pH control of P. pastoris without the need for continuous neutralisation.

Alanine↗
PubMed2002

Molecular cloning of a laccase isozyme gene from Pleurotus sajor-caju and expression in the heterologous Pichia pastoris host.

The Psc lac4 gene from Pleurotus sajor-caju has been cloned and expressed in the heterologous host Pichia pastoris, under the control of the AOX1 methanol inducible promoter. The native Ple. sajor-caju laccase signal sequence was effective in directing the secretion of lac4 expressed in Pic. pastoris. The control of media pH and temperature was found to be important in obtaining sufficient quantities of the protein to allow purification and subsequent biochemical characterization. The recombinant Psc Lac4 was purified to electrophoretic homogeneity and was shown to be immunologically related to Pleurotus eryngii Lac1. The purified laccase was estimated to have a molecular mass of around 59 kDa, to have a carbohydrate content of approximately 7% and a calculated pI of 4.38. The enzyme oxidized the substrates 2,2-azinobis-(3-ethylbenzthiazoline-6-sulphonate) (ABTS), 2,6-dimethoxyphenol, syringaldazine and guaiacol, exhibiting optimal pHs of 3.3, 6, 6.5 and 7 respectively. With ABTS as substrate the enzyme displayed optimal activity at 35 degrees C and pH 3.5. The enzyme was strongly inhibited by sodium azide and thioglycolic acid but not by EDTA.

Cloning, Molecular↗
PubMed2002

Early cervical cancer rescreening.

INTRODUCTION: The extent of early cervical rescreening, defined as rescreening earlier than the recommended interval for a given initial test result, is difficult to determine mainly because the testing history of women is incomplete, especially with newer population based screening registers. METHODS: Estimation of early rescreening is based on analysis of a 1 month cohort of women (February 1997) recorded on the New South Wales Pap Test Register (PTR) who initially tested negative and who had no recorded history of a positive test result. For the purposes of estimating early rescreening rates and sources of multiple screening occurring within the recommended 2 yearly screening interval for New South Wales, the cohort excluded the estimated proportion of women with an unrecorded history of a positive result. Approaches to exclusion were different for women with a history of a high grade result (CIN2 or higher) or a low grade result (CIN1 or lower). RESULTS: Characteristic rescreening peaks occurred at 6, 12, 18, 24 and 27 months according to negative result category. The rescreening peak at 27 months illustrates the effect of the PTR late reminder system. After adjusting the cohort for estimated proportions of women with a history of a lesion, the number of women estimated to have rescreened early was approximately 156 000 over 1997-8, and the early rescreening rate was estimated as 15.3% of women who have a Pap test. A feasible target for reducing rescreening through service provider interventions was estimated to be a reduction of 7.4%, based on reducing the overscreening proportion from 15.3% to 7.9% through truncating characteristic rescreening peaks to background levels of rescreening. This represents just under 200 000 screens that could be performed over 2 years on New South Wales women who are underscreened or unscreened without incurring additional costs due to screening. CONCLUSIONS: Reasonable estimates of early cervical rescreening can be derived but some assumptions in estimating the proportion of women with a positive test result history may be needed particularly if a screening programme is new and universal recording of screening data is only recent. Characteristic peaks, as departures from a background of random noise in time plots of rescreening indicate that a component of early rescreening is systemic and the chief source of such variation in screening behaviour would be service providers.

Adult↗
PubMed2001

Primary angiosarcoma of the femur: a diagnostic dilemma with a rare bone tumour.

We describe a rare case of high-grade primary angiosarcoma of the proximal femur in a 66-year-old man that proved fatal secondary to pulmonary metastases. The difficulties experienced in histological and immunohistochemical diagnosis of these tumours, and the resultant need for a high index of suspicion by surgeons in general and orthopaedists dealing with bone tumours in particular, is emphasized, as is the need for multidisciplinary management.

Aged↗
PubMed2001

Judging the accuracy of children's recall: a statement-level analysis.

Three experiments were conducted to examine fact finders' judgments of children's answers to cued recall questions about a recent dental visit. Participants performed better than chance at judging the correctness of the children's answers in all 3 experiments, and judgment accuracy was consistently better when the children's answers were correct. Judgment performance did not decline when confidence information was removed, and when all confidence information was removed, the best performance was obtained by parents and by professionals who work with children. The findings of these experiments provide support for the use of written transcripts in presentations of child testimony and highlight the importance of child- and event-related knowledge in judgments of children's testimony.

Adolescent↗
PubMed2000

Growth of Lactococcus lactis strains at low water activity: correlation with the ability to accumulate glycine betaine.

Lactococcus lactis strains were divided into two groups based on their ability to grow in the presence of an upper limit of either 2% w/v NaCl (sensitive) or 4% w/v NaCl (tolerant). Growth inhibition of NaCl tolerant strains was substantially relieved by glycine betaine which was accumulated in significant amounts when growing at low water activities (a(w)). Very little accumulation of glycine betaine occurred during growth of the NaCl sensitive strains. The NaCl tolerant strains had substantial levels of glycine betaine transport activity in vitro, whereas the NaCl sensitive strains had little or no such activity. A low a(w) sensitive mutant of L. lactis subsp. cremoris MG1363 (NaCl tolerant) was isolated following ISS1 insertional mutagenesis. This mutant was inhibited at an a(w) of 0.988 produced by addition of 2% w/v NaCl or the equivalent glucose concentration (0.58 M). The mutant did not accumulate glycine betaine when growing at low a(w), and did not transport glycine betaine when assayed in vitro.

Betaine↗
PubMed2000

The treatment of tetanus with intrathecal baclofen.

The treatment of severe tetanus generally requires prolonged mechanical ventilation. We describe two cases managed with continuous intrathecal infusion of baclofen via a subcutaneous tunnelled spinal catheter and an abdominal injection port. Baclofen, by diminishing spasms and spasticity, allowed reduced sedation and paralysis requirements. This potentially decreases the time and resources required for intensive care management. Complications include sedation, hypotension and CSF infection. After appropriate dose adjustment, baclofen improves the management of severe tetanus.

Aged↗
PubMed1999

Comparison of digital subtraction angiography with gadolinium-enhanced magnetic resonance angiography in the diagnosis of renal artery stenosis.

Renal artery stenosis (RAS) is a treatable cause of hypertension and renal failure for which no ideal screening technique is currently available. We evaluated the use of dynamic gadolinium-enhanced magnetic resonance angiography (MRA) for the diagnosis of RAS. Sixty-two patients with secondary hypertension were enrolled in the study. All patients had conventional renal angiography and gadolinium enhanced MRA. The sequence used was a 3D FMP SPGR sequence with the following parameters (TR: 26 ms, TE: 6.9 ms, flip angle 40 degrees, field of view 36 x 36 cm, matrix 246 x 256, 1 excitation). Gadolinium 0.3 mmol/kg was administered and 60 1. 5-mm-thick partitions were obtained over a duration of 3.5 min. The MRA images were then compared with conventional digital subtraction angiography (DSA) images. Conventional DSA demonstrated 138 renal arteries, whereas gadolinium-enhanced MRA demonstrated 129 (93 %). Twenty-one renal artery stenoses and four occluded arteries were seen at conventional DSA. Gadolinium-enhanced MRA had a sensitivity of 88 %, specificity of 98 %, accuracy of 96 %, positive predictive value of 92 % and negative predictive value of 97 % when compared with conventional DSA. Gadolinium-enhanced MRA is an accurate technique for identifying patients with RAS. It is less sensitive in picking up accessory renal arteries.

Angiography, Digital Subtraction↗
PubMed1999

Expression of Fas (CD95/APO-1) ligand by human breast cancers: significance for tumor immune privilege.

Breast cancers have been shown to elicit tumor-specific immune responses. As in other types of cancer, the antitumor immune response fails to contain breast tumor growth, and a reduction in both the quantity and cytotoxic effectiveness of tumor-infiltrating lymphocytes (TILs) is associated with a poorer prognosis. Fas ligand (FasL) induces apoptotic death of activated lymphocytes that express its cell surface receptor, FasR (CD95/APO-1). FasL-mediated apoptosis of activated lymphocytes contributes to normal immune downregulation through its roles in tolerance acquisition, immune response termination, and maintenance of immune privilege in the eye, testis, and fetus. In this report, we demonstrate that breast carcinomas express FasL. Using in situ hybridization and immunohistochemistry, we show that breast tumors constitutively express FasL at both the mRNA and protein levels, respectively. FasL expression is prevalent in breast cancer: 100% of breast tumors (17 of 17) were found to express FasL, and expression occurred over more than 50% of the tumor area in all cases. By immunohistochemistry, FasR was found to be coexpressed with FasL throughout large areas of all the breast tumors. This suggests that the tumor cells had acquired intracellular defects in FasL-mediated apoptotic signaling. FasL and FasR expression were independent of tumor type or infiltrative capacity. FasL expressed by tumor cells has previously been shown to kill Fas-sensitive lymphoid cells in vitro and has been associated with apoptosis of TILs in vivo. We conclude that mammary carcinomas express FasL in vivo as a potential inhibitor of the antitumor immune response.

Breast Neoplasms↗
PubMed1999

Evaluation of dynamic gadolinium-enhanced breath-hold MR angiography in the diagnosis of renal artery stenosis.

OBJECTIVE: The aim of our study was to evaluate a three-dimensional gadolinium-enhanced breath-hold MR angiography sequence using standard MR gradients in detecting renal artery stenosis. SUBJECTS AND METHODS: Forty-two patients referred for angiography for suspected renal artery stenosis underwent both conventional digital subtraction angiography (DSA) and MR angiography. MR angiography was performed on a 1.5-T scanner with standard gradients. A fast multiplanar spoiled gradient-echo sequence was used with the following parameters: TR/TE, 10.3/1.9; flip angle, 45 degrees; field of view, 36 x 32 cm; matrix size, 256 x 128; one excitation; volume thickness, 70 mm; and partitions, 28. Gadolinium was administered IV as a dynamic bolus of 30-40 ml. Conventional and MR angiographic images were interpreted by two radiologists in consensus. RESULTS: DSA revealed 87 renal arteries, of which 79 were in 35 patients with native kidneys and eight arteries were in seven patients with transplanted kidneys. Gadolinium-enhanced MR angiography showed 85 (98%) of 87 renal arteries. Seventeen patients had 20 significant (>50% stenosis) renal artery stenoses and five patients had five occluded renal arteries revealed by DSA. MR angiography revealed 85 renal arteries (98%), 20 stenoses (100%), and five occlusions (100%). Gadolinium-enhanced MR angiography led to one false-positive interpretation for renal artery stenosis and no false-negative interpretations. Thus, the sensitivity, specificity, and accuracy of MR angiography for renal artery stenosis were 100%, 98%, and 99%, respectively. CONCLUSION: The MR angiography pulse sequence we used was an effective and reliable technique for the diagnosis of renal artery stenosis. The sequence can be performed on widely available MR equipment that does not require fast gradient hardware.

Adult↗
PubMed1997

Chronic neuropathic pain and its control by drugs.

The medical treatment and some currently known aspects of the aetiology of five neurogenic pain states are discussed. Neurogenic pain can be described as pain resulting from noninflammatory dysfunction of the peripheral or central nervous system without nociceptor stimulation or trauma. The enormity of the field has limited this review to post-herpetic neuralgia, complex regional pain syndromes, phantom pain, trigeminal neuralgia and diabetic neuralgia. Evidence suggests that many neurogenic pain states are not effectively controlled. This may be due in part to a lack of understanding of the aetiology of these conditions and to the lack of high quality studies evaluating existing treatments. A compact review of the literature is presented with some treatment options and possible future directions. Where appropriate surgical management and physical therapy have been discussed; however, a thorough appraisal of nondrug treatments was not the main priority of this review.

Adult↗