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Biomedical subjects

I Wong

Publications and source records attributed to I Wong.

At least 19 recordsLinked to original sources
PubMed2006

Medicines for children licensed by the European Medicines Agency (EMEA): the balance after 10 years.

OBJECTIVE: The 1995-2005 balance of EMEA activities in the field of paediatric medicines was evaluated, taking into account the number both of drugs authorised for children and paediatric studies supporting the Marketing Authorisation (MA). METHODS: Data on drugs authorised by EMEA were extracted from EPARs (European Public Assessment Reports). Active substance, year of approval, anatomical, therapeutic and chemical (ATC) code, indication, orphan status, ages, and registrative clinical studies characteristics were assessed. RESULTS: The percentage of authorised substances for paediatrics is 33.3%. This percentage decreased or increased when different subsets of medicines were considered [medicines for children under 2 years (23.4%), N-ATC code drugs (6%) and orphan drugs (46.4%)]. A total of 165 trials were included in the MA dossiers of 51 drugs at the time of approval, and additional 22 studies were added to the dossiers of 12 active substances submitted for paediatric variations. PK and Efficacy/Safety studies were performed for 32 (52%) active substances, while either one PK or one Efficacy/Safety study was carried out for 43 (69%) and 45 (73%) substances, respectively. CONCLUSIONS: This report demonstrates that the total number of paediatric medicines approved by EMEA is stable over the 10-year period, while an increase in drugs to treat serious or orphan diseases has been observed. In addition, under the Centralised Procedure, a valuable number of paediatric trials have been submitted to support drug approval.

Adolescent↗
PubMed2006

Physical and microbiological stability of an extemporaneous tacrolimus suspension for paediatric use.

OBJECTIVE: An extemporaneous suspension of tacrolimus for paediatric use has recently been developed but poor bioavailability and erratic plasma concentrations were observed during clinical use. It was not clear whether this was due to changes in the physical properties of the suspension during storage. The aim of this work was to investigate the physical and microbiological stability over the recommended 8-week shelf-life of this extemporaneous tacrolimus suspension. METHODS: Suspensions (0.5 mg/mL) were custom made by a special manufacturer under Good Manufacturing Practice conditions. The procedure involved mixing tacrolimus capsule contents into Ora Plus and Simple Syrup (1 : 1) using a mortar and pestle followed by an homogenization step. The particle sizes of the suspensions were measured using a MasterSizer. A light microscope equipped with polarizers was used to visualize any particle size changes or crystal growth. Viable bacterial and fungal contamination was assessed using standard colony count techniques on solid media. The suspensions were kept at 22-26 degrees C and evaluated weekly. RESULTS: The volume mean diameter d((4,3)) from laser diffraction did not change significantly. Light microscopy did not reveal any significant change in particle size or crystal growth. Contamination by viable and culturable micro-organisms could not be detected. CONCLUSION: The suspension was physically (particle size) and microbiologically stable during the 8-week study period suggesting other factors including poor dosing could be responsible for the pharmacokinetic variation observed during clinical use which warrants further investigation.

Biological Availability↗
PubMed2005

Safety and efficacy of using the LigaSure vessel sealing system for securing the pedicles in vaginal hysterectomy: randomised controlled trial.

OBJECTIVE: To assess the safety and efficacy of using the LigaSure vessel sealing system for securing the pedicles during vaginal hysterectomy in comparison with the conventional method of securing the pedicles by suture ligation. DESIGN: Randomised controlled trial. SETTING: Gynaecology Department, Benenden Hospital, Kent. POPULATION: One hundred and sixteen women undergoing vaginal hysterectomy were prospectively randomised to either LigaSure (Group I) or suture ligation (Group II) for securing the pedicles. METHODS: Data of patients were collected prospectively. Statistical analysis was performed using the Mann-Whitney U test, chi(2) and Fisher's exact test as appropriate. MAIN OUTCOME MEASURES: Operating time, operative blood loss and peri-operative complications. RESULTS: The operating time was significantly shorter in the LigaSure group compared with the control group (P < 0.04). There was no statistical significant difference between the two groups in operative blood loss (P= 0.433), but peri-operative haemorrhagic complications were less frequent in the LigaSure group (0%vs 6.8%, P= 0.057). Four patients in the control group required either conversion to laparotomy because of bleeding, return to theatre for immediate post-operative haemorrhage or readmission for vault haematoma, whereas none in the LigaSure group had bleeding from unsecured pedicles. CONCLUSION: The LigaSure vessel sealing system is a safe alternative for securing pedicles in vaginal hysterectomy when compared with conventional suture ligation. Larger studies are required to determine its place in gynaecological surgery.

Blood Loss, Surgical↗
PubMed2004

Pharmaceutical care for elderly patients shared between community pharmacists and general practitioners: a randomised evaluation. RESPECT (Randomised Evaluation of Shared Prescribing for Elderly people in the Community over Time) [ISRCTN16932128].

BACKGROUND: This trial aims to investigate the effectiveness and cost implications of 'pharmaceutical care' provided by community pharmacists to elderly patients in the community. As the UK government has proposed that by 2004 pharmaceutical care services should extend nationwide, this provides an opportunity to evaluate the effect of pharmaceutical care for the elderly. DESIGN: The trial design is a randomised multiple interrupted time series. We aim to recruit 700 patients from about 20 general practices, each associated with about three community pharmacies, from each of the five Primary Care Trusts in North and East Yorkshire. We shall randomise the five resulting groups of practices, pharmacies and patients to begin pharmaceutical care in five successive phases. All five will act as controls until they receive the intervention in a random sequence. Until they receive training community pharmacists will provide their usual dispensing services and so act as controls. The community pharmacists and general practitioners will receive training in pharmaceutical care for the elderly. Once trained, community pharmacists will meet recruited patients, either in their pharmacies (in a consultation room or dispensary to preserve confidentiality) or at home. They will identify drug-related issues/problems, and design a pharmaceutical care plan in conjunction with both the GP and the patient. They will implement, monitor, and update this plan monthly. The primary outcome measure is the 'Medication Appropriateness Index'. Secondary measures include adverse events, quality of life, and patient knowledge and compliance. We shall also investigate the cost of pharmaceutical care to the NHS, to patients and to society as a whole.

Aged↗
PubMed2002

Measuring the incidence of lower limb ulceration in the Chinese population in Hong Kong.

OBJECTIVE: This retrospective study set out to examine the incidence, patient characteristics and current practice among patients with ulcers on the lower leg and foot who were under the care of the community nursing service of a regional hospital in Hong Kong. There is no clear differentiation between leg ulcers and foot ulcers in local practice in Hong Kong. METHOD: The nursing records of 819 subjects receiving treatment at home from the regional hospital's community nursing service were reviewed. All were active cases on 31 October 2000. RESULTS: The patients' median age was 76 (range: 36-100); 86% were aged over 65. Seventy-five percent of the patients had dressings changed daily, with 28 types of dressing being used. Nurses changed dressings in the patients' homes or in residential homes. Of the 94 patients with ulcers on the lower leg and foot, 75% had their dressings changed daily and only six less than three times a week. Fifty-four percent received regular podiatry clinic follow-up. CONCLUSION: Care of patients with ulcers on the lower limb represents a considerable workload for community nurses in Hong Kong, where little attention has been paid to the problem and current treatments. The number of patients with these ulcers cared for by community nurses in Hong Kong was high, with wide variations in management. Further investigation into evidence-based practice is needed to develop clinical guidelines and protocols that will achieve quality care. Research is now required in a clinical setting and for comparison with existing wound-care products.

Activities of Daily Living↗
PubMed2001

Parenteral drug administration errors by nursing staff on an acute medical admissions ward during day duty.

BACKGROUND: Parenteral therapy is a route of administration for drugs which are poorly absorbed via the oral route and it can provide a rapid response during an emergency. However, poorly prepared and/or administered parenteral therapy can cause potential harm to patients such as thrombus formation, severe hypersensitivity reactions and infection. Very few studies have investigated the incidence of medication errors associated with parenteral drug administration. OBJECTIVES: To determine the error rate during preparation and administration of parenteral medications by nursing staff and to propose strategies to reduce the error rate during parenteral administration. METHODS: A direct, disguised observation technique was used. The first author (JB) observed and recorded errors that occurred during the preparation and administration of parenteral medications on an admissions ward between 8.00 am and 4.30 pm from Monday to Friday for a 4-week period during December 1998. The staff were told that the observer was timing the administration; therefore they were not aware of the true nature of the study. This study was approved by the hospital audit committee. RESULTS: Drug administration was witnessed for a 4-week period providing 107 opportunities for error. 27 errors were observed which equated to an error rate of 25.2% [95% confidence interval (CI) 17.0 to 33.5%] including wrong time errors. Excluding wrong time errors, the most frequently occurring type of error, reduced the error rate to 10.3% (95% CI 3.8 to 14.9%). DISCUSSION: The error rate was lower than reported in the literature, this may be due to different methodologies, small sample size or effective nursing training and operating procedures. In the observed hospital, only nursing staff who have completed a training package are allowed to administer parenteral medications. CONCLUSION: Based on our small study, and 2 previous small studies, we can conclude that parenteral medication administration errors are common in the UK; however, these studies are too small-scale to detect rare and serious errors.

Cross Infection↗
PubMed1998

An outbreak of non-sexually transmitted gonococcal conjunctivitis in Central Australia and the Kimberley region.

From 13 February to 27 June 1997, 447 cases of gonococcal conjunctivitis were identified by Communicable Disease and Public Health Centres and Community Clinics in the Northern Territory, Western Australia and South Australia. The outbreak involved Aboriginal communities predominantly in Central Australia and the Kimberley region in Western Australia. This was the first outbreak recorded in the Kimberley region. It is not yet known whether the Kimberley cases were part of the larger Central Australian outbreak or whether they represented a separate and unrelated outbreak. Environmental factors associated with this outbreak were similar to those seen in previous outbreaks. Control measures were based on early recognition and treatment of index cases and identifying and treating contacts. Until sexually transmitted Neisseria gonorrhoeae is controlled in communities gonococcal conjunctivitis is likely to appear again. The role of oropharyngeal carriage of N. gonorrhoeae needs to be evaluated further.

Adolescent↗
PubMed1997

A two-site mechanism for ATP hydrolysis by the asymmetric Rep dimer P2S as revealed by site-specific inhibition with ADP-A1F4.

The Escherichia coli Rep helicase is a dimeric motor protein that catalyzes the transient unwinding of duplex DNA to form single-stranded (ss) DNA using energy derived from the binding and hydrolysis of ATP. In an effort to understand this mechanism of energy transduction, we have used pre-steady-state methods to study the kinetics of ATP binding and hydrolysis by an important intermediate in the DNA unwinding reaction--the asymmetric Rep dimer state, P2S, where ss DNA [dT(pT)15] is bound to only one subunit of the Rep dimer. To differentiate between the two potential ATPase active sites inherent in the dimer, we constructed dimers with one subunit covalently cross-linked to ss DNA and where one or the other of the ATPase sites was selectively complexed to the tightly bound transition state analog ADP-A1F4. We found that when ADP-A1F4 is bound to the Rep subunit in trans from the subunit bound to ss DNA, steady-state ATPase activity of 18 s(-1) per dimer (equivalent to wild-type P2S) was recovered. However, when the ADP-A1F4 and ss DNA are both bound to the same subunit (cis), then a titratable burst of ATP hydrolysis is observed corresponding to a single turnover of ATP. Rapid chemical quenched-flow techniques were used to resolve the following minimal mechanism for ATP hydrolysis by the unligated Rep subunit of the cis dimer: E + ATP <==> E-ATP <==> E'-ATP <==> E'-ADP-Pi <==> E-ADP-Pi <==> E-ADP + Pi <==> E + ADP + Pi, with K1 = (2.0 +/- 0.85) x 10(5) M(-1), k2 = 22 +/- 3.5 s(-1), k(-2) < 0.12 s(-1), K3 = 4.0 +/- 0.4 (k3 > 200 s(-1)), k4 = 1.2 +/- 0.14 s(-1), k(-4) << 1.2 s(-1), K5 = 1.0 +/- 0.2 mM, and K6 = 80 +/- 8 microM. A salient feature of this mechanism is the presence of a kinetically trapped long-lived tight nucleotide binding state, E'-ADP-Pi. In the context of our "subunit switching" model for Rep dimer translocation during processive DNA unwinding [Bjornson, K. B., Wong, I., & Lohman, T. M. (1996) J. Mol. Biol. 263, 411-422], this state may serve an energy storage function, allowing the energy from the binding and hydrolysis of ATP to be harnessed and held in reserve for DNA unwinding.

Adenosine Diphosphate↗
PubMed1997

Intrauterine insemination: effect of the temporal relationship between the luteinizing hormone surge, human chorionic gonadotrophin administration and insemination on pregnancy rates.

The optimal time period for intrauterine insemination (IUI) in relation to either luteinizing hormone (LH) surge or human chorionic gonadotrophin (HCG) administration leading to the best pregnancy rates has not been determined. In this study, 856 consecutive human menopausal gonadotrophin (HMG)-stimulated and 49 natural unstimulated IUI cycles carried out at a reproductive medicine unit affiliated with a tertiary centre were analysed in a retrospective fashion. There were three scenarios in the temporal relationship of the LH surge, HCG administration and artificial insemination. These were (group A) subjects who had an endogenous LH surge but were not given HCG; (group B) subjects who were given HCG after an observed LH surge, and (group C) subjects who were given HCG before the LH surge. The overall pregnancy rate (PR) was 16% per cycle. The PR was 9% in group A, 20% in group B and 14% in group C. The PR in group B was significantly better than group C (P = 0.04). In group B, the longer the time interval between the LH surge and HCG administration, the better the PR up to 20 h (P = 0.025); the timing of IUI based on the LH surge was not critical to the achievement of pregnancy within 3 days. In group C, PR improved with the increasing interval between HCG and IUI from <28 h up to 60 h. We conclude that a better PR is achieved if a spontaneous LH surge occurs before HCG administration, especially where the administration of HCG is delayed 8-20 h after an observed LH surge; the timing of IUI based on the LH surge is not critical to the achievement of pregnancy within 3 days.

Adult↗
PubMed1996

ATP hydrolysis stimulates binding and release of single stranded DNA from alternating subunits of the dimeric E. coli Rep helicase: implications for ATP-driven helicase translocation.

DNA helicases are motor proteins that unwind duplex DNA during DNA replication, recombination and repair in reactions that are coupled to ATP binding and hydrolysis. In the process of unwinding duplex DNA processively, DNA helicases must also translocate along the DNA filament. To probe the mechanism of ATP-driven translocation by the dimeric E. coli Rep helicase along single stranded (ss) DNA, we examined the effects of ATP on the dissociation kinetics of ssDNA from the Rep dimer. Stopped-flow experiments show that the dissociation rate of a fluorescent ss oligodeoxynucleotide bound to one subunit of the dimeric Rep helicase is stimulated by ssDNA binding to the other subunit, and that the rate of this ssDNA exchange reaction is further stimulated approximately 60-fold upon ATP hydrolysis. This ssDNA exchange process occurs via an intermediate in which ssDNA is transiently bound to both subunits of the Rep dimer. These results suggest a rolling or subunit switching mechanism for processive ATP-driven translocation of the dimeric Rep helicase along ssDNA. Such a mechanism requires the extreme negative cooperativity for DNA binding to the second subunit of the Rep dimer, which insures that the doubly DNA-ligated Rep (P2S2) dimer is formed only transiently and relaxes back to the singly ligated Rep (P2S) dimer. The fact that other oligomeric DNA helicases share many functional features with the dimeric Rep helicase suggests that similar mechanisms for translocation and DNA unwinding may apply to other dimeric as well as hexameric DNA helicases.

2-Aminopurine↗
PubMed1996

ATPase activity of Escherichia coli Rep helicase crosslinked to single-stranded DNA: implications for ATP driven helicase translocation.

To examine the coupling of ATP hydrolysis to helicase translocation along DNA, we have purified and characterized complexes of the Escherichia coli Rep protein, a dimeric DNA helicase, covalently crosslinked to a single-stranded hexadecameric oligodeoxynucleotide (S). Crosslinked Rep monomers (PS) as well as singly ligated (P2S) and doubly ligated (P2S2) Rep dimers were characterized. The equilibrium and kinetic constants for Rep dimerization as well as the steady-state ATPase activities of both PS and P2S crosslinked complexes were identical to the values determined for un-crosslinked Rep complexes formed with dT16. Therefore, ATP hydrolysis by both PS and P2S complexes are not coupled to DNA dissociation. This also rules out a strictly unidirectional sliding mechanism for ATP-driven translocation along single-stranded DNA by either PS or the P2S dimer. However, ATP hydrolysis by the doubly ligated P2S2 Rep dimer is coupled to single-stranded DNA dissociation from one subunit of the dimer, although loosely (low efficiency). These results suggest that ATP hydrolysis can drive translocation of the dimeric Rep helicase along DNA by a "rolling" mechanism where the two DNA binding sites of the dimer alternately bind and release DNA. Such a mechanism is biologically important when one subunit binds duplex DNA, followed by subsequent unwinding.

Adenosine Triphosphatases↗
PubMed1996

ATPase activity of Escherichia coli Rep helicase is dramatically dependent on DNA ligation and protein oligomeric states.

The Escherichia coli Rep helicase catalyzes the unwinding of duplex DNA using the energy derived from ATP binding and hydrolysis. Rep functions as a dimer but assembles to its active dimeric form only on binding DNA. Each promoter of a dimer contains a DNA binding site that can bind either single-stranded (S) or duplex (D) DNA. The dimer can bind up to two oligodeoxynucleotides in five DNA-ligation states: two half-ligated states, P2S and P2D, and three fully-ligated states, P2S2, P2D2, and P2SD. We have previously shown that the relative stabilities of these ligation states are allosterically regulated by the binding and hydrolysis of ATP and have proposed an "active rolling" model for DNA unwinding where the enzyme cycles through a series of these ligation states in a process that is coupled to the catalytic cycle of ATP hydrolysis [Wong, I., & Lohman, T.M., (1992), Science 256, 350-355]. THe basal ATPase activity of Rep protein is stimulated by ss DNA binding and by protein dimerization. We have measured the steady-state ATPase activities of Rep bound to dT(pT)15 in each distinct ss DNA ligation state (PS, P2S, and P2S2) to compare with our previous measurements with unligated Rep monomer (P) [Moore, K.J.M., & Lohman, T.M. (1994) Biochemistry 33, 14550]. We find the ATPase activity of Rep is influenced dramatically by both dimerization and ss DNA ligation state, with the following kcat values for ATP hydrolysis increasing by over 4 orders of magnitude: 2.1 x 10(-3) s(-1) for P, 2.17 +/- 0.04 s(-1) for PS, 16.5 +/- 0.2 s(-1) for P2S, and 71 +/- 2.5 s(-1) for P2S2 (20 mM Tris-HCl, pH 7.5, 6mM NaCl, 5 mM MgCl2, 10% glycerol, 4 degrees C). The apparent KM's for ATP hydrolysis are 2.05 +/- 0.1 microM for PS and 2.7 +/- 0.2 microM for P2S. These widely different ATPase activities reflect the allosteric effects of DNA ligation and demonstrate that cooperative communication occurs between the ATP and DNA site of both subunits of the Rep dimer. These results further emphasize the need to explicitly consider the population distribution of oligomerization and DNA ligation states of the helicase when attempting to infer information about elementary processes such as helicase translocation based solely on macroscopic steady-state ATPase measurements.

Adenosine Triphosphatases↗
PubMed1995

Changing the differentiation program of hematopoietic cells: retinoic acid-induced shift of eosinophil-committed cells to neutrophils.

The mechanisms by which hematopoietic progenitor cells become lineage-committed remain poorly understood. A cloned subline of the AML14 cell line (AML14.3D10) that spontaneously differentiates to eosinophilic myelocytes in the absence of cytokine stimulation was obtained by limiting dilution. This subline exhibits augmented expression of interleukin-5 (IL-5) receptor alpha subunit mRNA and synthesizes all major eosinophil granule proteins. Exposure of this cell line to all-trans retinoic acid (ATRA) causes loss of eosinophilic granules and fast green staining within 48 hours, without cell death. In addition, mRNA for the IL-5 receptor alpha subunit becomes undetectable by 48 hours and the cells lose responsiveness to IL-5. Major basic protein, measured as a marker of eosinophilic granule content, decreases from more than 16 pg/cell to undetectable levels by 5 days after ATRA. Concomitant with the loss of major basic protein and fast green staining, surface expression of CD16 becomes detectable and is maximum by 10 days after ATRA. mRNA for the granulocyte colony-stimulating factor (G-CSF) receptor becomes detectable by day 5, and the cells become responsive to G-CSF. At this time, the cells appear morphologically as mature neutrophils and can reduce nitroblue tetrazolium. With continued culture, the neutrophilic cells die and the culture becomes repopulated with eosinophilic myelocytes. These findings show that it is possible to change the differentiation program of hematopoietic cells even after they show evidence of advanced lineage commitment. The AML14.3D10 subclone of AML14 will be a valuable model for study of the transcriptional regulation of the eosinophil and neutrophil differentiation programs and lineage-specific gene expression.

Base Sequence↗
PubMed1993

Heterodimer formation between Escherichia coli Rep and UvrD proteins.

DNA helicases catalyze the essential process of unwinding duplex DNA to form the single-stranded DNA intermediates required for DNA metabolic processes including replication, recombination, and repair. Most cells, possibly all, encode multiple helicases that function selectively in different processes, although some helicases can complement each other in vivo. Thus, although Escherichia coli can survive mutations or deletions of either the uvrD gene (encoding Helicase II) or the rep gene (encoding Rep helicase) separately, deletion of both rep and uvrD genes is lethal (Washburn, B. K., and Kushner, S. R. (1991) J. Bacteriol. 173,2569-2575). The Rep and UvrD polypeptides share approximately 40% sequence homology, and we have previously shown that both form homodimeric species and that the Rep homodimer appears to be the functionally active helicase. We report here that these two proteins can also interact in vitro to form a heterodimer. The heterodimer appears to be energetically more stable than the Rep homodimer but less stable than the UvrD homodimer under our conditions. The observation of Rep/UvrD heterodimer formation in vitro opens up the intriguing possibility that the heterodimer may play a physiologically important role that is distinct from the role of the Rep or UvrD homodimers. Therefore, considerations of the role of either protein in DNA metabolic processes, such as replication and repair, must include a potential role for a Rep/UvrD heterodimer.

Adenosine Triphosphatases↗
PubMed1993

A double-filter method for nitrocellulose-filter binding: application to protein-nucleic acid interactions.

Nitrocellulose-filter binding is a powerful technique commonly used to study protein-nucleic acid interactions; however, its utility in quantitative studies is often compromised by its lack of precision. To improve precision and accuracy, we have introduced two modifications to the traditional technique: the use of a 96-well dot-blot apparatus and the addition of a DEAE membrane beneath the nitrocellulose membrane. Using the dot-blot apparatus, an entire triplicate set of data spanning 20-24 titrant concentrations can be collected on a single 4.5 x 5 inch sheet of nitrocellulose, obviating the need to manipulate separate filters for each titration point. The entire titration can then be quantitated simultaneously with direct two-dimensional beta-emission imaging technology. The DEAE second membrane traps all DNA that does not bind to the nitrocellulose, enabling a direct determination of the total amount of DNA filtered. This measurement improves precision by allowing the amount of DNA retained by the nitrocellulose to be normalized against the total amount of DNA filtered. The DEAE membrane also permits a more accurate quantitation of filter-retention efficiency and nonspecific background retention based on free DNA rather than total DNA filtered. The general approach and methods of analysis to obtain equilibrium binding isotherms are discussed, using as examples our studies of the Escherichia coli Rep protein, a helicase, and its interactions with short oligodeoxynucleotides.

Base Sequence↗