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Biomedical subjects

P Wilkinson

Publications and source records attributed to P Wilkinson.

At least 91 records · Page 5Linked to original sources
PubMed1991

A tint to reduce eye-strain from fluorescent lighting? Preliminary observations.

The rapid modulation of light from fluorescent lamps is responsible for eye-strain and headaches. The modulation is greater at certain wavelengths than at others, and it can therefore be reduced by wearing tinted spectacles. A tint was designed: (1) to minimize the luminous pulsation of light from conventional halophosphate fluorescent lamps; (2) to avoid as much as possible any concomitant increase in the pulsation from triphosphor lamps; (3) to interfere with colour perception as little as possible; and (4) to have a cosmetically acceptable colour appearance. The four design criteria conflict. A compromise design is described, together with case histories of patients who appear to have benefited from the use of the tint.

Adult↗
PubMed1991

Pharmacokinetics of ampicillin-sulbactam in healthy elderly and young volunteers.

The pharmacokinetics of ampicillin-sulbactam in elderly subjects (65 to 85 years; group 3, n = 8), compared with those in middle-aged (41 to 64 years; group 2, n = 8) and younger (20 to 40 years; group 1, n = 8) subjects, were investigated. A single 2-g dose of ampicillin combined with 1 g of sulbactam in 60 ml of intravenous solution was administered to each subject over a 30-min period. Blood and urine samples were taken at baseline and serially over an 8.5-h period following the infusion. Ampicillin and sulbactam concentrations were assayed by high-performance liquid chromatography on a reversed-phase C-8 column. The mean levels in serum of both ampicillin and sulbactam were significantly higher for samples from group 3: for ampicillin from 1 through 8.5 h, and for sulbactam for the same time interval except at 5.5 h (P less than or equal to 0.05). The mean urinary excretion of both ampicillin and sulbactam was lowest, and urinary concentrations were highest in group 3. The areas under the serum drug concentration-time curve, the half-lives, and the maximum concentrations in serum were greatest, while the total clearance was lowest, for group 3 for both ampicillin and sulbactam. These results are consistent with a prolongation of antimicrobial activity of ampicillin-sulbactam in the elderly compared with that in younger subjects.

Adult↗
PubMed1991

Pulmonary microvascular permeability in patients with severe mitral stenosis.

Patients with rheumatic mitral stenosis often have no pulmonary oedema despite considerably increased pulmonary venous pressure. Pulmonary microvascular permeability was measured non-invasively by a previously validated method of double isotope scintigraphy with indium-113m and technetium-99m. This permits calculation of an index reflecting transferrin efflux and thus, indirectly, the microvascular permeability. Fifteen patients with severe mitral stenosis (defined as valve area less than 1.0 cm2) were compared with a control group of 11 patients with mild coronary artery disease. The permeability index was significantly lower in patients with mitral stenosis than in the control group. Furthermore, the extent of reduction of the permeability index correlated with the severity of mitral stenosis as reflected by the Gorlin valve area. This finding may account for the relative resistance of these patients to pulmonary oedema despite chronic pulmonary venous hypertension.

Adult↗
PubMed1991

Treatment of infant sleep disturbance by trimeprazine in combination with extinction.

Chronic sleep disturbance is a common problem in preschool children. Prescription and non-prescription sedatives provide short-term palliative relief. Behavioral extinction by withdrawal of parental attention is enduringly effective but may be distressing short-term because of postextinction bursts of intense activity by the child. This study evaluated the effects of combining extinction and sedative medication (trimeprazine tartrate), prescribed in a reducing dose over the first 10 days of extinction. Control groups received either extinction alone or a placebo administered double-blind. After baseline, all subjects reduced their sleep disturbance to low levels, the extinction and placebo groups declining slowly, the medication group abruptly. These gains were maintained at follow-up. Measures of infant security and maternal anxiety showed improvements with treatment.

Arousal↗
PubMed1990

Analysis of naturally occurring deletion variants of African swine fever virus: multigene family 110 is not essential for infectivity or virulence in pigs.

A comparison of uncloned African swine fever virus isolates with their cloned counterparts revealed the presence of genetic variants in three out of seven uncloned field virus populations tested. Five different virus clones were isolated from the uncloned KIR69 virus stock by limit dilution. Structural analysis of the variants showed that they differed by single deletions of 10-16 kilobases in the region located between 6.8 and 27 kilobases from the left DNA terminus. There was no homology between DNA sequences immediately to the left and right of the deletions indicating that the mechanism generating deletion variants was not homologous recombination. The alignment of the restriction maps of the variants with those of other virus isolates indicated that two of the variants lacked the whole multigene family 110. This was confirmed by hybridization of the viral DNA with a degenerate oligonucleotide probe. Each virus variant replicated to high titer and was virulent in domestic pigs. Therefore, the multigene family 110 was not required for viral replication or virulence in domestic pigs. The virus variants were stable upon repeated passage in swine macrophages, indicating that the generation of variants is not a frequent genetic event in vitro.

African Swine Fever↗
PubMed1989

Regional lung microvascular permeability using dual isotope scintigraphy.

We have extended the dual isotope probe technique of Basran et al. for the measurement of pulmonary microvascular permeability (PMVP) to include gamma camera data acquisition and functional imaging of the plasma protein accumulation index (PPA) throughout the lung fields. The study group consisted of 11 patients with possible increased PMVP following the drainage of a pleural effusion or the evacuation of air from a pneumothorax, and 11 control patients. The PPA was calculated (1) for probe data, (2) on a pixel by pixel basis for the camera data, the results being stored in a functional image and (3) for four pixel x four pixel regions of interest positioned over the lung fields using the functional image and raw data as a guide. Functional images of the control group showed uniformly low PPAs throughout the lung fields. Nine of the eleven patients in the effusion/pneumothorax group showed discrete areas of increased PPA on the functional images. In the effusion/pneumothorax group, the re-expanded lung four pixel x four pixel ROI PPA values were significantly higher than the nonexpanded lung ROI values (p less than 0.001). The re-expanded lung ROI values were also significantly higher than the mean of the left and right lung ROIs in the control group (p less than 0.01). Five of the eleven patients in the effusion/pneumothorax group had probe PPAs that differed significantly from zero. We believe that probe positioning problems in the absence of sufficient clinical guidelines were largely responsible for there being no overall significant difference in the probe PPAs between the two study groups.

Adult↗
PubMed1989

Clinical pharmacokinetics of antibacterial drugs in the elderly. Implications for selection and dosage.

A review of the clinical pharmacokinetics of antibiotics in the healthy elderly reveals that for most compounds a decrease occurs in renal clearance (associated with age-related decreases in renal function), as well as a prolonged half-life and increased area under the plasma concentration-time curve. These changes are amplified in the sick infected elderly. It is important that the treating physician be aware of the potential side-effects of antimicrobial agents, and whenever possible choose those which are associated with the least adverse effects. Individual patient variability, including underlying diseases and other prescribed medications, must be taken into account when dosage is selected. beta-Lactam compounds have a remarkable safety record: specifically in the elderly, their therapeutic/toxic ratio is much higher than that observed with aminoglycosides. Regimens for this class of drugs in the elderly should maintain antibiotic concentrations above the minimum inhibitory concentrations for maximum efficacy. In the treatment of elderly patients, it is suggested that dosage and interval be based on estimated or measured creatinine clearance. Usually, for drugs that are excreted primarily by the kidney (i.e. amino-glycosides, beta-lactams and quinolones), dosage intervals must be increased when there is an associated fall in creatinine clearance. The pharmacokinetic parameters suggest that as an alternative to increasing dosage interval the usual dose may be decreased, but further studies are necessary for confirmation.

Aged↗
PubMed1987

A randomized trial of two types of adjuvant chemotherapy in radiotherapy-treated patients with clinical stages I and II high-grade non-Hodgkin's lymphoma.

This paper reports the 8-year results of comparing the use of two types of adjuvant chemotherapy following involved field radiotherapy for clinical stages I and II high-grade non-Hodgkin's lymphoma. Twenty-four patients received 6 weeks of VAP plus 2 years of oral maintenance chemotherapy, and 30 had six cycles of CMOPP. Four patients were not in complete remission at completion of i.v. chemotherapy (CR rate 91%). Ten patients (18.5%) have relapsed (VAP/M = 5; CMOPP = 5), with only two of these remaining alive, both of them being disease free. There have been three deaths from intercurrent causes, one from malignant melanoma and the other two from myocardial infarction. The relapse-free survivals at 2, 5 and 8 years were 80%, 76% & 76% respectively. The overall survivals at the same time points were 86%, 72% & 68%. There were no significant differences in either relapse-free or overall survival for either of the two treatment groups. The shorter period of weekly intravenous chemotherapy (VAP/M) was better tolerated than 36 weeks of CMOPP, and the former appears to produce equivalent results.

Adolescent↗
PubMed1985

An assessment of the prevalence of hepatitis B among health care personnel in Victoria.

The prevalence of past infection with hepatitis B virus in health care personnel was investigated by questionnaire and by a serological survey of personnel in a representative selection of Victorian hospitals and institutions. According to the available data, hepatitis B does not appear to have been a major infection problem among health care personnel in Victoria. The only occupational group that clearly is at an increased risk of acquiring the infection is the dental profession. Nursing staff members in institutions for the mentally retarded may also be at a higher risk. The findings of this investigation were used as a basis to frame recommendations for the vaccination of health care workers in Victoria against hepatitis B.

Australia↗
PubMed1985

Radon diffusion modelling.

A mathematical model has been developed that examines the ingress of radon into houses, through a vertical crack in an otherwise impervious concrete floor. Initially, the model considered the diffusive flow of radon from its soil source and this simulation has highlighted the dependency of the flux of radon into the house on the magnitude of various parameters, such as the diffusion coefficient of radon in soil. A preliminary investigation of the modelling of pressure-driven flow into a building is presented, and the potential of this type of analysis is discussed.

Diffusion↗
PubMed1985

Theoretical aspects of the design of a passive radon dosemeter.

Some mathematical aspects of the development and design of a passive radon dosemeter are considered. In particular, a mathematical model is presented that is concerned with the gaseous diffusion of radon into a confined region bounded by a plastic material of known diffusion coefficient. The relationship between the time-integrated radon concentrations, inside and outside a sealed plastic container are derived. Estimates of the exposure of people to radon can be made using the time integrated radon concentration inside a calibrated container containing a CR-39 etched-track device. As a consequence of the analysis, it is possible to design a passive radon dosemeter that will be accurate, resistant to moisture and whose response will be independent of rapid variations in radon concentration. The possibility of using a container of this type for the measurement of diffusion coefficients is discussed.

Humans↗
PubMed1985

Oral administration of grass pollen to hay fever patients. An efficacy study in oral hyposensitization.

Oral hyposensitization is still widely used in the treatment of allergic diseases, but controlled studies proving a beneficial effect are lacking. Fifty-eight hay fever patients were admitted to a double-blind placebo efficacy study in oral hyposensitization. An enterosoluble tablet containing timothy whole pollen or placebo was taken daily. Preseasonally, the actively treated patients received 4,315,000 PNU (880,260 AUR) and totally for 6 months 8,915,000 PNU (1,818,660 AUR). Such high doses have never been tried in similar studies. A new principle has been used - "the pollen count interval method" - in the evaluation of symptom and medication score. The study failed to prove any beneficial effect of oral hyposensitization measured by symptom score, medication score, nasal provocation test or skin prick test. There was no change in timothy specific IgE and IgG which could be caused by the treatment. The possibility that oral hyposensitization might be an effective treatment of hay fever in the future is discussed, but it is concluded that the present regimens cannot be recommended.

Administration, Oral↗
PubMed1985

Mental ability, symbolic play and receptive and expressive language of young children with Down's syndrome.

The relationship between measures of mental ability, symbolic play and expressive and receptive language was investigated in a sample of 73 children with Down's syndrome (mean CA 48.9 months, range 19-90 months; mean MA 30.4 months, range 13-73 months). Language delay became increasingly apparent with age, and more so in boys than girls. There was no significant difference between mental ages derived from standard ability tests and corresponding age equivalent scores of the Lowe and Costello symbolic play test. A developmental progression of play similar to that seen in non-handicapped groups was found. However, it is suggested that the use of a more detailed scoring system would be informative.

Child↗