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Biomedical subjects

R Walker

Publications and source records attributed to R Walker.

At least 217 records · Page 12Linked to original sources
PubMed1994

Prevalence of HPV DNA in cervical specimens in women with renal transplants: a comparison with dialysis-dependent patients and patients with renal impairment.

The aim of this study was to assess the prevalence of human papillomavirus (HPV) DNA in women who had received a renal transplant and to compare this with two control groups. Women who had a functioning renal transplant for greater than 6 months (n = 69) were compared with women on maintenance dialysis (n = 89) and women with impaired renal function (creatinine 0.15-0.39 mmol/l) (n = 22). Women were excluded if they had had a hysterectomy, were older than 65 years, or were not yet sexually active. A questionnaire and cervical scrape were obtained from each participant. The cervical scrape was analysed for HPV DNA using PCR and the L1 consensus primers. The participation rate of transplant patients, dialysis patients and those with impaired renal function ('normal' group) was 69, 68, and 78% respectively. The characteristics of the three groups of women at enrollment were similar. No cytological abnormalities were present in the 'normal' population but 11 of 89 patients on maintenance dialysis and nine of 69 transplant patients had cytological abnormalities of atypia or greater (P = 0.08 and P = 0.07, for 'normal' compared to dialysis and transplant groups respectively). One (4.5%) of the 'normal' women had evidence of HPV DNA, while 18 (20%) of patients on maintenance dialysis and 15 (22%) of transplant patients were positive (P = 0.07 and P = 0.05, for 'normal' compared to dialysis and transplant groups respectively). This study suggests that not only transplant recipients but also dialysis patients may have a higher prevalence of risk factors (cytological abnormalities and HPV DNA) for the development of cervical cancer.

Adult↗
PubMed1993

An analysis of the risk of exceeding the acceptable or tolerable daily intake.

The acceptable or tolerable daily intake (ADI or TDI) for food additives and contaminants is usually derived from chronic animal toxicity studies. The basis for the ADI or TDI is the determination of the no-observed effect level (NOEL) for the most sensitive toxicological effect in the most sensitive laboratory species. This "safe intake" for animals is then divided by a safety or uncertainty factor to allow for possible differences between the test species and humans and for possible differences within the human population. Therefore, the ADI or TDI is related to a toxic effect in the test species which is considered to be of relevance to humans. Any risk to humans who exceeded the ADI or TDI can only be assessed by reference to the dose-response for the toxicity giving rise to the NOEL. The duration of a human intake in excess of the ADI should also be considered in relation to the protocol used in such animal studies.

Animals↗
PubMed1993

A randomised double blind comparative study of low level laser therapy following surgical extraction of lower third molar teeth.

A randomised, double blind comparative study was undertaken to assess the efficacy of low level laser therapy in the reduction of postoperative pain and swelling in patients undergoing the extraction of bilaterally impacted mandibular third molar teeth. Healing of the sockets was also compared after 1 week. A group of 64 patients had one randomly-selected operation side treated with a semi-conductor laser and the other side with an apparently identical but non-operating model. Complete data were obtained from 52 of the 64 patients. The results showed that there was no evidence of a difference in pain and swelling on the third day after operation between laser and placebo sides. There was no difference between the two sides when they were assessed for healing 7 days after surgery.

Adolescent↗
PubMed1993

Contribution of phenolic and quinonoid structures in the mutagenicity of the edible mushroom Agaricus bisporus.

The objectives of this work were to establish the contribution of agaritine in the mutagenicity of ethanolic extracts from Agaricus bisporus and to examine the possible involvement of phenolic and quinonoid compounds in the mutagenic response to mushrooms. The mutagenic profile of agaritine in the Ames test, in the absence of an activation system, was different from that of the mushroom ethanolic extracts. Incorporation of rat hepatic cytosolic fractions as the activation system increased the mutagenicity of the mushroom ethanolic extracts in Salmonella typhimurium strain TA 104 but did not influence the mutagenicity of agaritine. It was concluded that agaritine is not the principal mutagenic component in the mushroom. The cytosol-induced mutagenicity of the mushroom extracts required NADPH, and was inhibited by dicoumarol and menadione. Moreover, the mutagenic response in the presence of cytosolic fractions was inhibited by superoxide dismutase, catalase, glutathione and dimethyl sulfoxide, thus implicating reactive oxygen species. Finally, tyrosinase, the enzyme converting mushroom phenols to quinones, increased the mutagenicity of the mushroom extracts. Collectively, the above results indicate that phenolic and quinonoid compounds, presumably through the generation of reactive oxygen species, may play a significant role in the mutagenicity of mushroom extracts.

Animals↗
PubMed1993

The effect of antioxidant supplementation on a serum marker of free radical activity and abnormal serum biochemistry in alcoholic patients admitted for detoxification.

Alcoholics admitted for detoxification were entered into a double blind placebo controlled trial of oral supplementation with an antioxidant cocktail (vitamin E, beta carotene, vitamin C and selenium) in order to determine the effect of this supplementation on the rate of resolution of a serum marker of free radical activity and abnormal serum biochemistry. The molar proportion of linoleic acid that was diene conjugated (a marker of free radical activity), was increased in the alcoholics 2.9% +/- 1.2 (mean +/- S.D.) compared to normal controls 1.3% +/- 0.6 (P < 0.0001) but fell at a similar rate during the first week of hospitalisation in supplemented and placebo-treated patients with a mean fall of 53.7% (+/- 16.4 S.D.) in the placebo group and 56.0% (+/- 23.7) (P = 0.32, NS) in the antioxidant supplemented group. Similarly, there was no difference in the rate of fall between serum aspartate transaminase (AST) concentration in the two groups: the placebo group falling by a mean of 68.9% (+/- 35.2) and the antioxidant supplemented group falling by 70.1% (+/- 10.0) (P = 0.41, NS) over the first 7 days of hospitalization. Alcoholics had low serum concentrations of vitamin E compared with controls (15.6 mg/l +/- 6.2 S.D.) which rose more in the supplemented group over the period of a week (7.7 mg/l +/- 4.4 to 21.6 mg/l +/- 5.1) (a mean rise of 180.5%) compared with the placebo group (8.6 mg/l +/- 6.8 to 9.6 mg/l +/- 5.7)--a mean rise of 11.6% (P = 0.006).(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

A study of the safety and survival of the adoptive transfer of genetically marked syngeneic lymphocytes in HIV-infected identical twins.

This phase I/II pilot project will evaluate the survival, tolerance, safety, and efficacy of infusions of activated, gene marked, syngeneic T lymphocytes obtained from HIV seronegative identical twins on the functional immune status of HIV infected twin recipients. T cells from each seronegative twin will be obtained by periodic apheresis, separated into CD4 and CD8 enriched populations by monoclonal antibody affinity binding techniques, induced to polyclonal proliferation with anti-CD3 and rIL-2 stimulation, transduced with distinctive neoR retroviral vectors, and expanded 10-1,000 fold in numbers during approximately 2 weeks of culture. These marked T cell fractions will then be infused into the seropositive twins and the survival of the uniquely marked T cell populations will be monitored by vector-specific PCR, while the recipients' functional immune status is monitored by standard in vitro and in vivo testing protocols. A total of 3 cycles of treatment will be given at intervals of 6 weeks between infusions.

Adolescent↗
PubMed1993

Criteria for local myocardial electrical activation: effects of electrogram characteristics.

Detection of local electrical myocardial activation by means of extracellular recordings is often difficult in the presence of polyphasic electrograms. The purpose of this investigation was to compare the ability of several variables to distinguish unipolar deflections due to local activation from those due to nonlocal activity. A model of polyphasic deflections based on atrial recordings during reentrant tachycardia was used to facilitate distinction of local and distant activity by methods independent of the test variables. The performance of variables were assessed by comparing areas under receiver operating characteristic curves. Optimal thresholds of test variables were identified by maximizing statistics which corrected for the pretest probability of local activation. We found that the greatest negative first derivative of the unipolar potential discriminated between local and distant ventricular signals, but performed less well than the ratio of the first derivative to the potential for distinguishing between local atrial signals and distant ventricular signals. A linear combination of the potential and the ratio of the first derivative and the potential performed well for all groups of signals studied. We conclude that optimal criteria for detecting local activation depends on the characteristics of the population of signals and that a statistical approach can be used to identify optimal criteria for a given population.

Action Potentials↗
PubMed1993

Short fat questionnaire: a self-administered measure of fat-intake behaviour.

A brief questionnaire has been developed to measure behaviour related to dietary fat intake. It is self-administered and self-coded. Mean completion time is about three minutes. Criterion validity was assessed by comparison with a well-established food frequency questionnaire using 124 adults from Newcastle and Sydney. The correlations with the questionnaire scores were: r = 0.55 for total fat as a percentage of total energy, r = 0.67 for saturated fat as a percentage of total energy, and r = 0.44 for polyunsaturated to saturated fat ratio. Reproducibility was assessed by re-use by 25 subjects after seven to nine months (r = 0.85). When used in a community survey of other 300 randomly chosen people in the Hunter Region, the mean scores for men and for women and among different age groups were significantly different. The questionnaire was strongly associated with other scales measuring attitudes, behaviour and knowledge related to low-fat diets. The questionnaire appears suitable for rapid self-assessment by subjects, and as it directs their attention to aspects of their diet which might need improvement, it could be used for health education. It might also be used for epidemiological studies to rank subjects broadly according to their fat-intake behaviour.

Adolescent↗
PubMed1993

Myocardial electrical propagation in patients with idiopathic dilated cardiomyopathy.

Myocardial propagation may contribute to fatal arrhythmias in patients with idiopathic dilated cardiomyopathy (IDC). We examined this property in 15 patients with IDC undergoing cardiac transplantation and in 14 control subjects. An 8 x 8 array with electrodes 2 mm apart was used to determine the electrical activation sequence over a small region of the left ventricular surface. Tissue from the area beneath the electrode array was examined in the patients with IDC. The patients with IDC could be divided into three groups. Group I (n = 7) had activation patterns and estimates of longitudinal (theta L = 0.84 +/- 0.09 m/s) and transverse (theta T = 0.23 +/- 0.05 m/s) conduction velocities that were no different from controls (theta L = 0.80 +/- 0.08 m/s, theta T = 0.23 +/- 0.03 m/s). Group II (n = 4) had fractionated electrograms and disturbed transverse conduction with normal longitudinal activation, features characteristic of nonuniform anisotropic properties. Two of the control patients also had this pattern. Group III (n = 4) had fractionated potentials and severely disturbed transverse and longitudinal propagation. The amount of myocardial fibrosis correlated with the severity of abnormal propagation. We conclude that (a) severe contractile dysfunction is not necessarily accompanied by changes in propagation, and (b) nonuniform anisotropic propagation is present in a large proportion of patients with IDC and could underlie ventricular arrhythmias in this disorder.

Adult↗
PubMed1993

Neoplastic meningitis as the presentation of occult primitive neuroectodermal tumors.

Seven children and young adults initially presented with subacute meningitis and/or increased intracranial pressure. The diagnosis of neoplastic meningitis secondary to a primitive neuroectodermal neoplasm was delayed by the absence of an obvious primary tumor. The neuroradiologic appearance was that of a basimeningeal infiltrative process, complicated by communicating hydrocephalus or "pseudotumor cerebri." Myelography was important in the diagnosis of disseminated meningeal malignancy in four cases. Cerebrospinal fluid cytologic diagnosis was insensitive but ultimately confirmed in five cases. All seven patients experienced progressive disease despite neuraxis radiotherapy and intensive chemotherapy; six have died. Systemic dissemination to bone and/or peritoneum occurred in three patients while on therapy. In two, a primary parenchymal brain or spinal cord tumor could not be identified at postmortem examination. The presentation of a primitive neuroectodermal tumor as subacute meningitis without an evident primary tumor heralds an aggressive and refractory neoplasm.

Adolescent↗
PubMed1993

Management of giant cell tumor of the tarsal bones: a report of nine cases and a review of the literature.

Giant cell tumor of the tarsal bones is uncommon and therapeutic options are ill defined. We report on nine cases of giant cell tumors of the tarsal bones treated by excision of the complete bone in 6 cases, partial excision in 1 case, and curettage and bone grafting in two cases. There was no recurrence at an average 25.8-month follow-up. Function after calcanectomy was satisfactory. Excision of the talus may or may not be followed by arthrodesis, but arthrodesis is essential after excision of all the other tarsal bones except the calcaneus. We advocate aggressive surgical measures in these cases; amputation should be reserved for recurrences only. Satisfactory function may be expected after excision of tarsal bones.

Adolescent↗
PubMed1993

Carboplatin and vincristine for recurrent and newly diagnosed low-grade gliomas of childhood.

PURPOSE: This study investigates the response rate to and toxicity of carboplatin and vincristine in children with recurrent low-grade gliomas (LGGs) or patients younger than 60 months with newly diagnosed LGGs. PATIENTS AND METHODS: Twenty-three children with recurrent and 37 children with newly diagnosed LGGs were treated with a 10-week induction cycle of carboplatin and vincristine, followed by maintenance treatment with the same drugs. Patients were evaluated for response to treatment and toxicity. RESULTS: Twelve of 23 (52% +/- 10%; 95% confidence interval [CI], 0.32 to 0.72) assessable children with recurrent disease had an objective response to treatment, which included a greater than 50% reduction in tumor size in seven of 23 (30% +/- 10%; 95% CI, 0.10 to 0.50). Twenty-three of 37 (62% +/- .08; 95% CI, 0.46 to 0.78) of newly diagnosed patients had an objective response, 16 of 37 (43% +/- 0.08%; 95% CI, 0.27 to 0.59) with greater than 50% reduction in tumor size. The majority of those with an objective response had diencephalic tumors (n = 29), but children with thalamic (n = 2), cortical (n = 1), and brain stem (n = 2) LGGs also responded to treatment. Of the 35 patients with objective response to treatment, the maximum response was seen in 25 after completion of induction and in the remaining 10 after two to six cycles of maintenance treatment. Forty-nine of 53 (92% +/- .04%) patients who were stable or improved after induction remain without progressive disease (PD). Hematologic toxicity was common, but resulted in cessation of therapy in only one patient. Six children have been removed from the study because of allergic reactions, which were considered to be carboplatin-associated. CONCLUSION: Carboplatin and vincristine have activity in children with recurrent and newly diagnosed progressive LGGs. Objective responses to treatment after chemotherapy can be seen. This drug regimen is relatively well tolerated, and further studies are indicated to define the role of this combination of drugs in children with newly diagnosed LGGs.

Adolescent↗