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Biomedical subjects

K Walker

Publications and source records attributed to K Walker.

At least 55 records · Page 3Linked to original sources
PubMed2000

The reliability of the American Knee Society Score.

We have investigated the reliability of the American Knee Society Score (AKS), a widely used functional outcome score for knee arthroplasty. 29 subjects were assessed in random order by 6 observers, each patient seen twice by each observer. The interobserver reference intervals were 16 points for the Knee Score (0-100 points) and 21 points for the Function Score (0-100 points). The intraobserver reference intervals were smaller, 11 points and 13 points for the Knee Score and the Function Score, respectively. The presence of arthritis in other joints and general debility did not affect the reliability of the scores. The more experienced observers had greater intraobserver reproducibility. Notably, we found moderate agreement between observers in the subjective variables, while the objective variables produced lower levels of agreement. The high inter- and intraobserver variations of the AKS makes estimation of score change questionable. Reliable use of the AKS would necessitate repeated evaluation by an experienced observer.

Arthroplasty, Replacement, Knee↗
PubMed2000

Detection of sequence variation in the HVII region of the human mitochondrial genome in 689 individuals using immobilized sequence-specific oligonucleotide probes.

We have developed a rapid, immobilized probe-based assay for the detection of sequence variation in the hypervariable segment II (HVII) of the mitochondrial DNA (mtDNA) control region. Using a panel of 17 sequence-specific oligonucleotide (SSO) probes immobilized on nylon membrane strips, we typed 689 individuals from four population groups. The genetic diversity value for each population was calculated from the frequency data, and the frequencies of distinct "mitotypes" in each group were determined. We performed DNA sequence analysis of 129 samples to characterize the sequences associated with "blanks" (absence of probe signals) and weak probe signals. Out of 689 samples, we observed five heteroplasmic samples (excluding the variable C-stretch beginning at position 303) using the immobilized SSO probe panel. The SSO probe strips were used for the analysis of shed hairs and bloodstains from several criminal cases in Sweden, one of which is described here. We conclude that this mtDNA typing system is useful for human identification and significantly decreases casework turnaround time.

Base Sequence↗
PubMed1999

Partial purification and characterization of acetyl coenzyme A: taxa-4(20),11(12)-dien-5alpha-ol O-acetyl transferase that catalyzes the first acylation step of taxol biosynthesis.

The acetylation of taxa-4(20),11(12)-dien-5alpha-ol is considered to be the third specific step of Taxol biosynthesis that precedes further hydroxylation of the taxane nucleus. An operationally soluble acetyl CoA:taxadienol-O-acetyl transferase was demonstrated in extracts of Taxus canadensis and Taxus cuspidata cells induced with methyl jasmonate to produce Taxol. The reaction was dependent on both cosubstrates and active enzyme, and the product of this acetyl transferase was identified by radiochromatographic and GC-MS analysis. Following determination of the time course of acetyl transferase appearance in induced cell cultures, the operationally soluble enzyme was partially purified by a combination of anion exchange, hydrophobic interaction, and affinity chromatography on immobilized coenzyme A resin. This acetyl transferase has a pI and pH optimum of 4.7 and 9.0, respectively, and a molecular weight of about 50,000 as determined by gel permeation chromatography. The enzyme shows high selectivity and high affinity for both cosubstrates, with Km values of 4.2 and 5.5 microM for taxadienol and acetyl CoA, respectively. The enzyme does not acetylate the more advanced Taxol precursors, 10-deacetylbaccatin III or baccatin III. This acetyl transferase is insensitive to monovalent and divalent metal ions, is only weakly inhibited by p-hydroxymercuribenzoate, N-ethylmaleimide, and coenzyme A, and resembles in general properties the few other O-acetyl transferases of higher plant origin that have been examined.

Acetyltransferases↗
PubMed1999

Ethnic identity and its relationship to self-esteem, perceived efficacy and prosocial attitudes in early adolescence.

This study examined the relationship of ethnic identity to self-esteem, perceived self-efficacy and prosocial attitudes. The sample included 100 male and female early adolescents, ranging from 11 to 13 years old, from different racial/ethnic backgrounds. Structural equations modeling was used to examine the latent structure of the multi-dimensional constructs and their interrelationships. Self-esteem and ethnic identity factors emerged which were related and which evidenced efficacy-mediated effects upon prosocial attitudes. The findings suggested that ethnic identity and self-esteem are distinct but related contributors to young people's perceptions of their ability to achieve academically, to find meaningful careers and to value prosocial means of goal attainment.

Adolescent↗
PubMed1999

Photoscreening for refractive errors in children and young adults with severe learning disabilities using the MTI photoscreener.

PURPOSE: To test the potential ability of the MTI photoscreener to facilitate screening for significant refractive errors in children and young adults with severe learning disabilities. METHODS: Thirty-eight patients with severe learning disabilities from a special school were examined with the photoscreener, and underwent cycloplegic refraction, an ophthalmological and an orthoptic examination. The age at examination, the cause of learning disability, the pupil size, the number of photographs required for accurate interpretation, the co-operation of the subject and the presence or absence of strabismus were recorded. An educational psychologist had performed a psychological assessment on all the children. The results of the cycloplegic retinoscopy were compared with the photorefraction results. RESULTS: A photorefraction was possible in 37 patients and cycloplegic refraction in all the patients. The patients had severe learning difficulties with an intelligence quotient of less than 50. All the patients had behavioural problems, 9 patients had associated cerebral palsy, 8 had chronic epilepsy, 1 patient was brain damaged from a non-accidental injury and 1 from a road traffic accident. The mean age of the patients was 10.0 +/- 4.9 years (range 3-18 years), the average pupil diameter during photoscreening was 6.1 +/- 0.9 mm (range 4-8 mm) and the average number of photographs required for each subject was 2.1 +/- 0.9 (range 1-4). The photoscreener detected 10 patients with a manifest strabismus. There was one false positive and one false negative result giving a sensitivity of 92.8% and a specificity of 90%. CONCLUSION: The examination of children with severe learning disabilities for refractive errors can be extremely difficult. The MTI photoscreener is an effective means of screening such children and young adults for refractive errors and strabismus so that the children with these abnormalities may be targeted for a more detailed evaluation.

Adolescent↗
PubMed1999

The effect of carbamazepine and sodium valproate on the blood and serum values of children from a third-world environment.

In third-world countries many children with epilepsy also suffer from malnutrition, anemia, liver disease, and immunosuppression. Doctors might have reservations about the use of anticonvulsants that could aggravate these disorders. The purpose of this study was to establish the prevalence of abnormal blood and serum values in children receiving carbamazepine or sodium valproate as monotherapy who attended a child neurology clinic serving a third-world community in Cape Town, South Africa Blood samples were taken at routine follow-up visits from 104 children who had been on carbamazepine or sodium valproate monotherapy for at least 6 months. Hematology, serum chemistry, immunoglobulins, and anticonvulsant levels were measured by standard laboratory procedures. Very few subjects had any values outside accepted normal ranges. When clinically indicated and available, carbamazepine and sodium valproate can be prescribed for children from a third-world environment. Frequent blood and serum testing is not necessary in asymptomatic individuals.

Adolescent↗
PubMed1999

Factors in cardiac risk stratification of candidates for renal transplant.

BACKGROUND: Renal transplant candidates are at high risk of fatal and nonfatal cardiac events. METHODS: This study evaluated five clinical risk factors--age at least 50 years, insulin-requiring diabetes mellitus, angina, congestive heart failure and an abnormal electrocardiogram (ECG) (excluding left ventricular hypertrophy)--that had been used in the first tier of a two-tiered prospectively applied risk stratification algorithm. RESULTS: Using multiple logistic regression analysis, age at least 50 years, abnormal ECG, and diabetes mellitus were independently predictive of cardiac death. Of the two remaining clinical risk factors, the presence of angina had independent predictive value for nonfatal cardiac events (myocardial infarction, coronary angioplasty, bypass surgery, and unstable angina). The independent predictive value of congestive heart failure approached statistical significance. CONCLUSION: Clinical risk-factor analysis is helpful in identifying renal transplant candidates at high risk for fatal or nonfatal cardiac events.

Algorithms↗
PubMed1999

The therapeutic potential of CXC chemokine blockade in acute inflammation in the brain.

Mammalian neurones of the central nervous system (CNS) are terminally differentiated, and there is little endogenous capacity of the CNS to repair itself. Peripheral tissue injury, disease or infection results in a stereotypical inflammatory response to protect the host from pathogens and to promote tissue repair. However, collateral or 'bystander' damage is characteristic of any inflammatory response. Thus, it is apparent that the CNS has evolved mechanisms to regulate tightly the acute inflammatory response, and in particular to restrict the recruitment of neutrophils, in an attempt to protect itself from the potentially damaging consequences of inflammation in the brain. However, neutrophils are not always excluded from the brain. Indeed, they are found in large numbers in the brain parenchyma following traumatic lesions, stroke lesions, and in rodents, during the 'window of susceptibility'. Therapy targeted at blocking excitotoxic cell death has not successfully transferred from rodent models of stroke to human stroke patients. Restricting leukocyte entry to the brain, thereby inhibiting the inflammatory response, may prove to be a more practical therapeutic approach. The evidence presented in this review suggests that antagonising the effects of CXC chemokines may represent one route to achieve this goal.

Journal Article↗
PubMed1998

Surgical treatment of carpal tunnel syndrome and trigger digits in children with mucopolysaccharide storage disorders.

The role of surgical intervention for carpal tunnel syndrome (CTS) and trigger digits in children with mucopolysaccharide storage disorders (MPSDs) has not been clearly defined, particularly as the treatment of the underlying disease has advanced to include bone marrow transplantation. This study reviews our experience in the treatment of CTS and trigger digits in 22 children with MPSDs who were evaluated for CTS by electromyographic (EMG)/nerve conduction velocity (NCV) testing. Seventeen children were diagnosed with CTS by EMG/NCV testing and were treated with bilateral open surgical release with or without flexor tenosynovectomy. The EMG/NCV testing revealed normal results in 5 patients who are subsequently being monitored. Forty-five digits in 8 children were diagnosed clinically with trigger digits. Nineteen digits were treated by annular pulley release alone. Twenty-six digits were treated by annular pulley release with partial flexor digitorum superficialis tendon resection. The average age at the time of hand surgery was 6.3 years, and at the time of follow-up, 9.6 years. Postoperative EMG/NCV testing in 7 children showed 1 with improvement and 6 with normalization. None of the patients undergoing carpal tunnel release went on to develop thenar atrophy or absent sensibility, as has been reported in untreated cases. Patients were evaluated for triggering digits both by preoperative tendon palpation and by intraoperative flexor tendon excursion at the time of open carpal tunnel release. All patients undergoing trigger release had improved active digital flexion seen at the final follow-up visit. Because of the very high incidence of CTS and trigger digits in this population, the authors currently recommend routine screening of EMG/NCV for all children with MPSDs. Early surgical intervention for nerve compression and stenosing flexor tenosynovitis can maximize hand function in these children.

Age Factors↗
PubMed1998

A 5 year strategic plan of action.

Exciting innovations for the new millennium as the NSW College of Nursing becomes more relevant, dynamic and accessible to its members.

Forecasting↗
PubMed1997

Structure of the monophosphoryl lipid A moiety obtained from the lipopolysaccharide of Chlamydia trachomatis.

Monophosphoryl lipid A was prepared from the lipopolysaccharide of Chlamydia trachomatis, converted to the methyl ester, and fractionated by reverse-phase high-performance liquid chromatography. The peak fractions were collected and analyzed by mass spectrometry. Matrix-assisted laser desorption/ionization and liquid secondary ion mass spectrometry of the first of two major high-performance liquid chromatographic fractions showed multiple quasi-molecular ions of MNa+ at m/z 1780, 1794, 1808, 1822, and 1836. The positive-ion liquid secondary ion mass spectrometry spectrum also showed a minor series of peaks at m/z 1916, 1930, 1944, 1958, and 1971, consistent with the formation of matrix adducts with 3-nitrobenzyl alcohol. Oxonium ions representing the distal subunit were observed at m/z 1057, 1071, 1085, 1099, and 1113. The second fraction was similarly analyzed and found to contain structural homologs of the first fraction. Based on this study, the major lipid A component of chlamydial lipopolysaccharide is a glucosamine disaccharide that contains five fatty acids and a phosphate in the distal segment. Three fatty acyl groups are in the distal segment, and two are in the reducing end segment. The acyloxyacyl group is located in the distal segment in amide linkage. Two structural series, differing by 14 atomic mass units in the reducing subunit, were observed. Chlamydial lipid A is complex and consists of at least 20 homologous structural components. The relatively low potency of Chlamydia trachomatis lipopolysaccharide in activating lipopolysaccharide-responsive cells might be related to the unusual fatty acid composition of the lipid A moiety.

Chlamydia trachomatis↗
PubMed1997

Supramolecular Materials: Self-Organized Nanostructures

Miniaturized triblock copolymers have been found to self-assemble into nanostructures that are highly regular in size and shape. Mushroom-shaped supramolecular structures of about 200 kilodaltons form by crystallization of the chemically identical blocks and self-organize into films containing 100 or more layers stacked in a polar arrangement. The polar supramolecular material exhibits spontaneous second-harmonic generation from infrared to green photons and has an adhesive tape-like character with nonadhesive-hydrophobic and hydrophilic-sticky opposite surfaces. The films also have reasonable shear strength and adhere tenaciously to glass surfaces on one side only. The regular and finite size of the supramolecular units is believed to be mediated by repulsive forces among some of the segments in the triblock molecules. A large diversity of multifunctional materials could be formed from regular supramolecular units weighing hundreds of kilodaltons.

Journal Article↗
PubMed1997

Clinical trial of moxidectin oral gel in horses.

A clinical trial carried out over 98 days was done to evaluate treatment of horses with moxidectin gel for efficacy as measured by (1) reduction in the production of parasite ova post treatment, (2) a comparison of the posttreatment parasite egg count suppression of moxidectin to ivermectin, and (3) assessment of the field safety, animal acceptance of the moxidectin formulation, and the utility of the moxidectin delivery device. One hundred and fifty Standardbred horses with naturally acquired parasite infections were used in the study. Moxidectin had more prolonged and greater suppressive influence than did ivermectin on reappearance and magnitude of strongyle egg counts post treatment. Differences were not observed between the capability of ivermectin or moxidectin to reduce and suppress low Parascaris equorum egg counts. Adverse reactions to treatments were not observed, and the utility of the moxidectin delivery syringe and animal acceptance of moxidectin treatment were satisfactory.

Administration, Oral↗
PubMed1997

Catecholamine modulatory effects of nepicastat (RS-25560-197), a novel, potent and selective inhibitor of dopamine-beta-hydroxylase.

1. Inhibitory modulation of sympathetic nerve function may have a favourable impact on the progression of congestive heart failure. Nepicastat is a novel inhibitor of dopamine-beta-hydroxylase, the enzyme which catalyses the conversion of dopamine to noradrenaline in sympathetic nerves. The in vitro pharmacology and in vivo catecholamine modulatory effects of nepicastat were investigated in the present study. 2. Nepicastat produced concentration-dependent inhibition of bovine (IC50 = 8.5 +/- 0.8 nM) and human (IC50 = 9.0 +/- 0.8 nM) dopamine-beta-hydroxylase. The corresponding R-enantiomer (RS-25560-198) was approximately 2-3 fold less potent than nepicastat. Nepicastat had negligible affinity (> 10 microM) for twelve other enzymes and thirteen neurotransmitter receptors. 3. Administration of nepicastat to spontaneously hypertensive rats (SHRs) (three consecutive doses of either 3, 10, 30 or 100 mg kg-1, p.o.; 12 h apart) or beagle dogs (0.05, 0.5, 1.5 or 5 mg kg-1, p.o.; b.i.d., for 5 days) produced dose-dependent decreases in noradrenaline content, increases in dopamine content and increases in dopamine/noradrenaline ratio in the artery (mesenteric or renal), left ventricle and cerebral cortex. At the highest dose studied, the decreases in tissue noadrenaline were 47%, 35% and 42% (in SHRs) and 88%, 91% and 96% (in dogs) in the artery, left ventricle and cerebral cortex, respectively. When tested at 30 mg kg-1, p.o., in SHRs, nepicastat produced significantly greater changes in noradrenaline and dopamine content, as compared to the R-enantiomer (RS-25560-198), in the mesenteric artery and left ventricle. 4. Administration of nepicastat (2 mg kg-1, b.i.d, p.o.) to beagle dogs for 15 days produced significant decreases in plasma concentrations of noradrenaline and increases in plasma concentrations of dopamine and dopamine/noradrenaline ratio. The peak reduction (52%) in plasma concentration of noradrenaline and the peak increase (646%) in plasma concentration of dopamine were observed on day-6 and day-7 of dosing, respectively. 5. The findings of this study suggest that nepicastat is a potent, selective and orally active inhibitor of dopamine-beta-hydroxylase which produces gradual modulation of the sympathetic nervous system by inhibiting the biosynthesis of noradrenaline. This drug may, therefore, be of value in the treatment of cardiovascular disorders associated with over-activation of the sympathetic nervous system, such as congestive heart failure.

Animals↗
PubMed1997

Cutting edges: deconstructive inquiry and the mission of the border ethnographer.

Research is an activity nursing 'cannot not want'. Such an imperative compels me to sketch out some theoretical borders of a hybrid postmodern methodological framework that I have called 'border' ethnography. It is a methodology suspended between a still authoritative modernity and an as yet only partially legitimate postmodernity. At one level this position is somewhat uncomfortably in a post-methodological terrain. The text that issues from such a tension-laden research space is, I argue, intensely autobiographical, inescapably ethnographic and inherently deconstructive. Ethno(autobio) graphy is a method 'on the run'; it destabilizes while it authorizes, it represents while it misrepresents, and it threatens to disintegrate as it comes into view. But, most importantly, it is the creature of a praxis-oriented endeavour not only to better understand a culture, but to actively intervene in its (re) production.

Anthropology, Cultural↗