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Biomedical subjects

L Turner

Publications and source records attributed to L Turner.

173 records · Page 10Linked to original sources
PubMedDate not supplied

Chloroform: exposure estimation, hazard characterization, and exposure-response analysis.

Chloroform has been assessed as a Priority Substance under the Canadian Environmental Protection Act. The general population in Canada is exposed to chloroform principally through inhalation of indoor air, particularly during showering, and through ingestion of tap water. Data on concentrations of chloroform in various media were sufficient to serve as the basis for development of deterministic and probabilistic estimates of exposure for the general population in Canada. On the basis of data acquired principally in studies in experimental animals, chloroform causes hepatic and renal tumors in mice and renal tumors in rats. The weight of evidence indicates that chloroform is likely carcinogenic only at concentrations that induce the obligatory precursor lesions of cytotoxicity and proliferative regenerative response. Since this cytotoxicity is primarily related to rates of formation of reactive, oxidative metabolites, dose response has been characterized in the context of rates of formation of reactive metabolites in the target tissue. Results presented here are from a "hybrid" physiologically based pharmacokinetic (PBPK) animal model that was revised to permit its extension to humans. The relevant measure of exposure response, namely, the mean rate of metabolism in humans associated with a 5% increase in tumor risk (TC05), was estimated on the basis of this PBPK model and compared with tissue dose measures resulting from 24-h multimedia exposure scenarios for Canadians based on midpoint and 95th percentiles for concentrations in outdoor air, indoor air, air in the shower compartment, air in the bathroom after showering, tap water, and food. Nonneoplastic effects observed most consistently at lowest concentrations or doses following repeated exposures of rats and mice to chloroform are cytotoxicity and regenerative proliferation. As for cancer, target organs are the liver and kidney. In addition, chloroform has induced nasal lesions in rats and mice exposed by both inhalation and ingestion at lowest concentrations or doses. The mean rate of metabolism associated with a 5% increase in fatty cysts estimated on the basis of the PBPK model was compared with tissue dose measures resulting from the scenarios already described, and lowest concentrations reported to induce cellular proliferation in the nasal cavities of rats and mice were compared directly with midpoint and 95th percentile estimates of concentrations of chloroform in indoor air in Canada. The degree of confidence in the underlying database and uncertainties in estimates of exposure and in characterization of hazard and dose response are delineated.

Air Pollutants↗
PubMedDate not supplied

Radiation regression patterns in treated retinoblastoma: 7 to 21 years later.

A retrospective review of cases on file at the Ophthalmic Oncology Center of The New York Hospital-Cornell Medical Center, New York was performed in order to examine the appearance of radiation regression patterns 7 or more years after successful treatment of retinoblastoma with external beam radiotherapy. Forty-eight patients were found to have 89 tumors in 57 eyes which were treated solely with external beam radiation; they were followed for a minimum of 7 years and had sufficient information available for analysis. All but five of the patients had bilateral retinoblastoma. Seventy-four of the 89 tumors continued to be ophthalmoscopically visible after 7 or more years. Taking into account those that did change between the time of first evaluation (usually at the completion of treatment) and final evaluation (7 or more years after treatment), the number of Type I regressions increased by 10.1%, Type IIs decreased by 19.1%, Type IIIs fell by 7.8%, Type IVs rose by 10.1%, and the number of tumors that disappeared increased by 6.8%. Type II remained the most common regression throughout the follow-up. The regression with the greatest potential for change was the Type II regression. The pretreatment volume of the tumor correlated with long-term radiation regression patterns. The smallest tumors (mean size 1.1 dd [disc diameter] or less in size) completely disappeared, while the largest (mean 9.9 dd) became Type I regressions.

Child↗
PubMedDate not supplied

Royal Brisbane Hospital--no lifting 1998.

In August of 1997 the Royal Brisbane Hospital commenced working towards the implementation of a no-lift policy in line with the Queensland Nurses' Union No Lifting by the Year 2000 policy. This is a report on that implementation.

Humans↗
PubMedDate not supplied

Incidence of cervical dyskaryosis in Ireland: report of a five-year audit.

The implementation of a national cervical screening programme in Ireland will require agreement on achievable standards in reporting cervical cytology similar to those published by the NHS cervical screening programme. Due to the opportunistic nature of screening in the Republic of Ireland, national incidence figures for uterine cervical disease are not available. An audit of our practice was performed to find the incidence of human papilloma virus related cervical disease in our population. Our laboratory reported 158,066 cases from 1996-2000. The overall rate of dyskaryosis increased from 3.6% to 7.9%, mostly due to increased low grade dyskaryosis (up from 2.3% to 6.0%). High grade dyskaryosis also increased (from 1.3% to 1.9%), particularly in the under-25 year age group who account for a growing proportion of high grade dyskaryosis (from 15.4% of all high grade diagnoses in 1996 to 23.0% in 2000). The positive predictive value of a diagnosis of high grade dyskaryosis remained stable between 76.0 and 79.5%. While opportunistic screening data may not be directly applicable to the entire screening population it is hoped that these data may form a foundation on which to estimate national incidence figures and define achievable standards for cervical screening cytology in Ireland.

Adult↗
PubMedDate not supplied

The development of the baboon prostate: ultrasound methodology, modelling, and natural history.

In order to evaluate the potential of ultrasound for serial, nontraumatic estimation of prostate size in the hamadryas baboon (Papio hamadryas), we adapted the technique of planimetric ultrasound to study a captive-bred colony of 30 male baboons (median age 8.4 years, range 3.3-17 years) including 4 long-term castrates. Most (19) were studied on another two occasions (at 33-and 43-day intervals) to estimate reproducibility of the prostate size (dimensions, volume) measurement. Prostatic dimensions were measured with a B-mode sector ultrasound using a 7.5-MHz transrectal transducer by planimetry at 2.5-mm steps from base to apex as well as the maximum three dimensions of the prostate. The planimetric volume estimate was reproducible (intraclass coefficient 0.81) with coefficient of variation (CV) of 24.3% for all, and 16.0% for mature, baboons. The prostate dimensions were also reproducible (CVs 7.9-13.4%). Prostate volume estimates based on the general ellipsoidal model were reasonably reproducible (19.9% for all, 12.9% for mature) but were biased in relationship to the planimetric volume (0.57 +/- 0.19, P = 0.004). Using the independent estimates of prostate volume and dimensions, we developed an empirical power-function model of prostate shape based on the generalized ellipsoidal model that was robust and unbiased (-0.07 +/- 0.15, P = 0.64) with respect to the planimetric volume. This model provides a simpler and accurate formula for prostate volume based on its three maximal dimensional measurements. The natural history of prostate growth in the hamadryas baboon was illustrated by sigmoidal correlations with age (ED50 = 6.0 years, plateau ED95 = 8.3 years), body weight (ED50 = 14.6 kg, ED96 = 16.1 kg), and testis volume (ED50 = 7.8 ml, ED95 = 18.4 ml). Between-animal variability among mature baboons was greater for prostate weight (27%) than body weight (10%), raising the possibility that a subgroup of these baboons may develop spontaneous age-related prostatic hyperplasia. These findings suggest that ultrasonic evaluation of prostate size in the hamadryas baboon may constitute a suitable model for spontaneous benign prostatic hyperplasia and for experimental studies of prostate growth, development, and hormonal regulation.

Animals↗