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Biomedical subjects

L Yuen

Publications and source records attributed to L Yuen.

At least 19 recordsLinked to original sources
PubMed2006

Effect of hyaluronidase on ocular motility and eyelid function in sub-Tenon's anaesthesia: randomised controlled trial.

PURPOSE: To assess the effect of hyaluronidase on eye and eyelid movements when used as an adjunct in sub-Tenon's anaesthesia. METHODS: A total of 60 patients who had sub-Tenon's anaesthesia prior to phacoemulsification surgery were divided into two equal groups in a double-masked randomised controlled fashion. Of these, Group A had 4 ml lignocaine 2%, while Group B had 4 ml lignocaine 2% with the addition of sodium hyaluronidase 75 IU/ml. Ocular motility, levator, and orbicularis oculi function were measured in all patients at 5 and 8 min. Levator function was scored from 0 (no function) to 3 (complete function) while orbicularis function was scored from 0 to 2. The score for ocular motility was the sum in four positions of gaze, each position scoring from 0 to 2. Results were compared using a nonparametric test. RESULTS: Group B achieved significantly better ocular and lid akinesia than Group A both at 5 and 8 min with P<0.01. The median scores for levator function at 5 and 8 min were 2 for Group A and 0 for Group B. For orbicularis function, the median scores at both time intervals were 2 for Group A and 1 for Group B. For ocular motility, the median score for Group A at 5 min was 3 and at 8 min was 2.5; for Group B at 5 min was 0.5 and at 8 min was 0. CONCLUSIONS: The addition of hyaluronidase in sub-Tenon's anaesthesia has a significant effect in improving ocular and lid (levator and orbicularis) akinesia.

Adjuvants, Anesthesia↗
PubMed2005

Chronic hepatitis B: recommendations for therapy based on the natural history of disease in Australian patients.

BACKGROUND: Chronic hepatitis B infection (CHB) is a major health problem in Australia and worldwide. CHB is associated with significant long-term morbidity and mortality. Well tolerated treatment is now available, however the development of resistance is common and the optimal timing of treatment is yet to be determined. Identifying the factors that influence the natural history of CHB may help determine which patients need treatment and when to start it. OBJECTIVE: To determine the demographics, clinical features and virological profile of Australian patients infected with CHB and the influence of these factors on disease activity and severity. STUDY DESIGN: Review of prospectively collected demographic, clinical and virological features of all patients positive for hepatitis B surface antigen (HBsAg) for more than 6 months who were referred to St. Vincent's Hospital liver clinics. Age, sex and ethnicity were correlated with hepatitis B e antigen status (HBeAg), HBV replication status (ALT and HBV DNA), genotype and liver histology. RESULTS: 703 chronic hepatitis B surface antigen positive patients were identified. The patients were predominantly male with an average age of 44. Eighty two percent of patients were born overseas, primarily from Asian (65%) and Mediterranean countries (14%). Two thirds (426) had an elevated ALT (median 79) at presentation. HBeAg was positive in 37%. Active viral replication, defined as abnormal ALT or positive HBVDNA, was present in 74%, 48% of whom were HBeAg negative. In a subset of 103 patients genotyped, 8% had genotype A, 29% B, 41% C and 22% D. Genotype correlated with ethnicity; patients infected with genotypes A were predominantly Caucasian, B and C were Asian, and D were Mediterranean. Of 296 (42%) patients who underwent liver biopsy, 76 (27%) had advanced fibrosis. Advanced fibrosis was associated with increasing age and Mediterranean ethnicity. CONCLUSION AND RECOMMENDATIONS: Perinatal or early childhood transmission is predominant mode of infection in Australia. Two thirds of this cohort had active replication and were at increased risk of developing cirrhosis and/or hepatoma. Advanced disease was associated with age and ethnicity. HBeAg negative CHB accounts for almost half of all those with active viral replication. This parallels the rise in this form of CHB in Asia and the Mediterranean basin. Screening should be offered to people born in, or with parents born in areas of high endemnicity. To detect the development of active disease, patients with positive HBsAg but normal ALT should have liver function tests done 6 monthly and those with elevated ALT should be referred for consideration of therapy, irrespective of HBeAg status.

Antiviral Agents↗
PubMed2004

Microfracture and changes in energy absorption to fracture of young vertebral cancellous bone following physiological fatigue loading.

STUDY DESIGN: Fifty-five human thoracolumbar vertebrae were randomly fatigue loaded and analyzed. OBJECTIVES: The purpose of this study was to explore the relationship between fatigue loading, trabecular microfracture, and energy absorption to fracture in human cadaveric thoracolumbar vertebrae. BACKGROUND: Although trabecular microfractures are found in vivo and have been produced by fatigue loading in vitro, the effect of the level of physiologic fatigue loading on microfracture and energy absorption has not been investigated. METHODS: Fifty-five human thoracolumbar vertebrae (T11-L4) were randomly divided into 5 groups: 1) control (no loading, n = 6); 2) axial compression to yield (n = 7); and 3-5) 20,000 cycles of fatigue loading at 2 Hz (each n = 14). The level of fatigue loading was determined as a proportion of the yield load of Group 2 as follows: 10% (Group 3), 20% (Group 4), and 30% (Group 5). Half of the specimens in groups 3 to 5 were used for radiographic and histomorphometric analysis to determine microfracture density and distribution, whereas the other half were tested to determine the energy absorption to yield failure. RESULTS: No radiographic evidence of gross fracture was found in any of the groups following fatigue loading. A mean 7.5% increase in stiffness was found in specimens subject to cyclic loading at 10% of yield stress (Group 3). Fatigue at 20% (Group 4) and 30% of yield stress (Group 5) caused significantly higher (P < 0.05) increases in mean stiffness of 23.6% and 24.2%, respectively. Microfracture density increased from 0.46/mm in Group 3 to 0.66/mm in Group 4 and 0.94/mm in Group 5 (P < 0.05). The energy absorbed to failure decreased from 21.9 J in Group 3 to 18.1 J and 19.6 J in Groups 4 and 5, respectively (P < 0.05). CONCLUSIONS: Fatigue loading at physiologic levels produced microfractures that are not detectable by radiography. Increased fatigue load results in an increase in microfracture density and decrease energy absorbed to fracture, indicating a reduced resistance to further fatigue loading.

Absorptiometry, Photon↗
PubMed2001

Plasminogen binding is increased with adipocyte differentiation.

The purpose of this study was to examine the role of the plasminogen system in the development of adipose tissue. Plasminogen binding capacity was determined in differentiated and undifferentiated cells from adipose tissue of plasminogen deficient mice and 3T3 cells, a well-characterized tissue culture model. In 3T3 cells, plasminogen binding was fivefold higher in differentiated cells compared to the undifferentiated cells. Inhibition of binding by carboxyl-terminal lysine analogs was similar for the differentiated and undifferentiated cells with tranexamic acid > EACA > lysine. The binding of plasminogen was concentration-dependent and approaches saturation in the both cell types. The number of plasminogen binding sites was tenfold higher in the differentiated compared to the undifferentiated cells. In isolated mature fat cells and stromal cell cultures from mouse adipose tissue, plasminogen binding was also higher in the differentiated mature fat cells and differentiated stromal cells compared to undifferentiated stromal cells. Plasminogen binding was elevated in the differentiated cells from the Plg-/- mice compared to cells from the WT mice. These results suggest that the plasminogen system plays an important role in adipose tissue development.

3T3 Cells↗
PubMed2001

High level excretion of Norwalk-like virus following resolution of clinical illness.

We report the case of an elderly woman excreting high levels (about 5 x 10(5) virions per gram of faeces) of Norwalk-like virus (NLV) in the absence of any clinical symptoms of gastroenteritis. Analysis by reverse transcription, polymerase chain reaction and DNA sequencing was carried out on a 342-nucleotide region of open reading frame 1. This indicated that the NLV belonged to genogroup 2 and was more closely related to the Camberwell subgroup, the most common circulating in southeast Australia at present, than to the Norwalk and Mexico viruses.

Aged↗
PubMed2000

Primary sarcoma of the ribs in a large, mixed breed dog.

A 9-year-old, 30-kg, neutered male, mixed breed dog was referred for en bloc resection of a tentatively diagnosed costal chondrosarcoma. Light microscopic examination of the excised mass confirmed osteosarcoma. Adjuvant chemotherapy with 4 treatments with carboplatin was initiated. There have been no signs of metastases 5 months postsurgery.

Animals↗
PubMed1999

The hepatitis B virus-trimera mouse: a model for human HBV infection and evaluation of anti-HBV therapeutic agents.

Previous studies have demonstrated the feasibility of implantation of human blood cells or tissues in lethally irradiated mice or rats, radioprotected with SCID mouse bone marrow cells: The Trimera system. In the present study, we describe the development of a mouse Trimera model for human hepatitis B virus (HBV) infection. In this model, viremia is induced by transplantation of ex vivo HBV-infected human liver fragments. Engraftment of the human liver fragments, evaluated by hematoxylin-eosin staining and human serum albumin mRNA expression, was observed in 85% of the transplanted animals 1 month postimplantation. Viremia levels were determined in these mice by measuring serum HBV DNA using polymerase chain reaction (PCR), followed by dot-blot hybridization. HBV DNA is first detected 8 days after liver transplantation. Viremia attains a peak between days 18 and 25 when HBV infection is observed in 85% of the transplanted animals. The HBV-Trimera model was used to evaluate the therapeutic effects of human polyclonal anti-HBs antibodies (Hepatect) and of two reverse-transcriptase inhibitors, lamivudine (3TC) and beta-L-5-fluoro-2',3'-dideoxycytidine (beta-L-5FddC). Treatment of HBV-Trimera mice with these drugs effectively reduced both the percentage of infected animals and the viral load in their sera. Treatment cessation resulted in rebound of viral load, indicating HBV replication upon drug withdrawal. These results show that the HBV-Trimera model represents a novel experimental tool for simulating human HBV infection and evaluating potential anti-HBV therapeutic agents.

Animals↗
PubMed1999

Front-line police officers' practices, perceptions and attitudes about the enforcement of impaired driving laws in Canada.

A survey of front line police officers' practices, perceptions and attitudes regarding detection of impaired driving, processing of driving while impaired (DWI) charges, criminal court proceedings and DWI sanctions was conducted across Canada. A sample of 1545 officers of all jurisdictions across the country, representative of different types of police services (i.e. national, provincial, municipal) and types of policing (i.e. traffic, general duty) were surveyed by mail. The results, based on a 71% response rate, indicate that: an average of 7.5 charges/year are laid by officers resulting mainly from erratic driving; videotaping and mobile breath testing could improve efficiency of DWI enforcement; it takes an average of 2 h 48 min to process each DWI charge; about 2/3 of officers say plea bargaining occurs at least sometimes; the average length of DWI trial is over 4 h; less than half of officers think Crown Attorneys are adequately prepared for DWI cases; about 3/4 of officers think the accused escapes conviction on a legal technicality at least sometimes; about 30% of officers say short-term licence suspensions and other forms of discretion are used at least sometimes; DWI places fifth in priority among 15 offences, up from eighth in a 1981 survey; DWI is a priority for most police management but human resources are not adequate; and there is greater support for administrative than for Criminal Code changes. Multiple regressions indicated that the number of DWI charges laid by officers depended mainly on the officers' personal priority regarding DWI enforcement. The results suggest that many officers want to enforce DWI laws but that the numerous procedural and legal barriers that they confront often force them to exercise discretion in the laying of DWI charges.

Accidents, Traffic↗
PubMed1999

A high throughput colorimetric cell proliferation assay for the identification of human cytomegalovirus inhibitors.

A colorimetric assay based on the cleavage of the tetrazolium salt WST-1 has been developed for human cytomegalovirus (HCMV) antiviral susceptibility testing and adapted to a microtiter plate format. Optimal conditions were determined and the standard routine assay was calibrated with a viral input of 0.05-0.10 plaque forming unit (p.f.u.)/cell with a density of 2000 cells/well in a 96-well microtiter plate for an incubation period of 7 days. Ganciclovir (9-(2-hydroxy-1(hydroxymethyl) ethyoxymethyl) guanine; DHPG), and cidofovir ((S)-1-(3-hydroxy-2-phosphonylmethoxypropyl) cytosine; HPMPC) were used as positive control test compounds to validate the assay. The effective EC50 concentration values obtained with the two antiviral compounds in the present assay were in good agreement with plaque reduction assay results performed in parallel experiments. This method presents the advantage of being easy and rapid to perform, reliable, reproducible, and convenient for use in a high throughput screening capacity.

Antiviral Agents↗
PubMed1998

Design and synthesis of monocyclic beta-lactams as mechanism-based inhibitors of human cytomegalovirus protease.

Mechanism based inhibitors of HCMV protease have been designed based on the monocyclic beta-lactam nucleus, which have been shown to acylate the viral enzyme in a time dependent manner. SAR in a series of monocyclic beta-lactam N-ureas, has defined the size and relative stereochemistry of the C-3 substituent producing a low micromolar inhibitor 17b with good aqueous stability and selectivity over the mammalian serine proteases.

Drug Stability↗
PubMed1997

Cloning, sequencing and transcriptional analysis of the Choristoneura fumiferana entomopoxvirus spheroidin gene.

The Choristoneura fumiferana entomopoxvirus (CfEPV) spheroidin gene was identified and localized on three XbaI restriction fragments (total size 4.73 kb). The fragments were cloned and sequenced. The spheroidin gene had an open reading frame of 2997 nucleotides encoding a putative protein with a predicted size of 115 kDa. Sequence analysis indicated that the putative protein contained 14 potential N-glycosylation sites (Asn-X-Thr; Asn-X-Ser), that are probably not used since the protein migrates on SDS-PAGE as a 115 kDa band. The protein is rich in cysteine residues (34), which explains the need for reducing agents when dissolving the occlusion bodies with alkali. The spheroidin gene sequence contains motifs characteristic of the late genes of poxviruses. These include the typical TAAATG sequence at the beginning of the coding region and two early gene termination signals (TTTTTNT) in the untranslated region of the gene. The promoter region has three TAA termination signals immediately upstream of the ATG start site. Spheroidin (SPH) appears to be conserved among different EPVs. There was 82.2% identity and 97.2% similarity at the amino acid level between the SPHs of CfEPV and Amsacta moorei EPV. Less conservation was seen with the SPH from Melolontha melolontha EPV (39.8% identity and 73.4% similarity). Transcriptional analyses of the spheroidin gene by Northern blots showed that the transcript had a size of approximately 3 kb, which is in agreement with the length of the ORF. Primer extension results, anchor PCR and sequencing confirmed that there was a poly (A)17 tract at the 5' end of the spheroidin gene transcript, a structure typical of late gene transcripts of poxviruses.

Amino Acid Sequence↗
PubMed1991

The 5' noncoding region sequence of the Choristoneura biennis entomopoxvirus spheroidin gene functions as an efficient late promoter in the mammalian vaccinia expression system.

About 100 nucleotides of DNA sequence at the 5' noncoding region of the Choristoneura biennis entomopoxvirus spheroidin gene was chemically synthesized and inserted into a vaccinia expression vector, interrupting the vaccinia thymidine kinase gene. When the bacterial beta-galactosidase gene was introduced downstream of this sequence and a recombinant vaccinia virus containing these inserts was obtained by homologous recombination, beta-galactosidase was shown to be expressed at a high level late in the vaccinia infection cycle. The level of beta-galactosidase expression was four- to fivefold higher with this spheroidin-vaccinia recombinant virus than with a similar recombinant in which the beta-galactosidase gene was under the control of the vaccinia 7.5-kDa promoter. Primer extension and S1 mapping of the 5' terminus of the beta-galactosidase transcript located the transcription initiation site within the spheroidin DNA sequence, confirming the promoter nature of this DNA sequence in the vaccinia system. Dot blot analysis indicated that the difference in beta-galactosidase expression with these two recombinant viruses can be attributed to the difference in their transcript levels. We also demonstrated that full promoter activity encoded in the spheroidin 5' noncoding sequence was contained within a 38-nucleotide DNA fragment.

Animals↗
PubMed1991

DNA sequence of the nucleoside triphosphate phosphohydrolase I (NPH I) of the Choristoneura biennis entomopoxvirus.

The DNA sequence of an open reading frame (ORF) corresponding to a Choristoneura biennis entomopoxvirus putative late gene was determined. Residing within an 8-kp EcoRI viral genomic fragment, this ORF is 1944 nucleotides long, encoding a basic protein (pI 9.83) with a predicted molecular weight of 76,000 Da. Computer analysis indicates a 36.4% homology between this ORF and the vaccinia nucleoside triphosphate phosphohydrolase I (NHP I) gene, with substantially greater homology (60%) in two domains believed to be involved in ATP binding. The entomopoxvirus ORF contains 78% AT residues; and like other poxvirus late genes, it possesses the conserved TAAAT motif at the 5' terminus of the gene.

Amino Acid Sequence↗
PubMed1991

Permeability of blood-brain and blood-nerve barriers in experimental diabetes mellitus in the anaesthetized rat.

Diabetes was induced with streptozotocin in rats weighing about 160 g. These were maintained with age-matched controls for up to 14 months, blood glucose being periodically monitored. Half the diabetic and control rats received the aldose reductase inhibitor, Ponalrestat, in their diet. At 3 weeks, 6-7 months and 13-14 months, the vascular permeability in regions of brain, and in optic and sciatic nerves, were measured by maintaining radiotracers in the bloodstream--125I-albumin (100 min), [14C]sucrose (60 min) and 131I-albumin (5 min)--followed by tissue sampling and counting at termination. 131I-albumin estimated residual intravascular plasma. Diabetes of up to 13-14 weeks caused no measurable increase in the sucrose permeability of microvessels in eight different brain regions, in optic or in sciatic nerve. At 3 weeks of diabetes, sucrose permeability in all brain regions and in optic nerve was reduced relative to that in controls. Extravascular albumin entry into different regions of brain and optic nerve was insignificant and insensitive to diabetes, except in the hypothalamus and optic nerves where it was raised with increasing duration of diabetes. In sciatic nerve, extravascular albumin distribution was markedly increased by diabetes, but sucrose permeability was not demonstrably affected. At the level used in the diet, Ponalrestat reduced the sorbitol content of diabetic sciatic nerve but did not protect again the increased permeability to albumin.

Aldehyde Reductase↗
PubMed1991

Albumin escape from microvessels in kidney, heart and skeletal muscle in experimental diabetes mellitus in the anaesthetized rat.

Diabetes was induced with streptozotocin in rats weighing about 160 g. These were maintained with age-matched controls for up to 14 months, blood glucose being periodically monitored. Half the diabetic and control rats received the aldose reductase inhibitor, Ponalrestat, in their diet. Distribution of volumes of 131I-albumin (5 min) and 125I-albumin (100 min) were estimated in various tissues at 3 weeks, 6-7 months and 13-14 months of diabetes. The former space was assumed to represent the intravascular plasma space, while the latter was taken to include both the extravascular and intravascular albumin volumes in the kidney. In heart and skeletal muscle, equilibration between the specific activities of extravascular albumin and of plasma albumin was not assumed to be complete at 100 min. In the cortex and medulla of kidney, the extravascular albumin pool increased significantly at 13-14 months of diabetes (for both, P less than 0.01). Significantly increased entry of albumin into the interstitium occurred at 6 months (P less than 0.05) and at 13-14 months (P less than 0.01) in skeletal muscle, and at 13-14 months (P less than 0.05) in heart. The intravascular plasma volumes were not influenced by diabetes and the aldose reductase inhibitor had no effect at any time in either diabetic or control rats. These findings indicate increased movement of plasma albumin into the interstitium in the late phase of diabetes in the heart, skeletal muscle and in the kidney. Enlargement of the interstitial albumin pool is likely to affect the fluid balance between capillary and interstitium and may contribute to the effect of diabetes on the function of these organs.

Albumins↗
PubMed1991

Identification and sequencing of the Choristoneura biennis entomopoxvirus DNA polymerase gene.

A degenerate oligonucleotide probe corresponding to a highly conserved amino acid sequence in several DNA polymerases was used to locate the DNA polymerase gene in the Choristoneura biennis entomopoxvirus. Southern blot analysis of the entomopoxvirus genome using the degenerate oligonucleotide probe showed specific interaction between the probe and an eight kilobasepair EcoRI fragment from the entomopoxvirus genome. Sequencing this EcoRI fragment revealed an open reading frame 2892 nucleotides in length, capable of encoding a protein about 115 kilodaltons. Homology search of this open reading frame against other proteins indicated a high degree of homology in four distinct regions with DNA polymerases from other organisms. The highest degree of homology (24.9% at the amino acid level) was found between the vaccinia DNA polymerase gene and the entomopoxvirus open reading frame.

Amino Acid Sequence↗