A theoretical model for the production of Ac-225 for cancer therapy by neutron capture transmutation of Ra-226.

Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. We are investigating the reduction of radium by transmutation by bombarding Ra-226 with high-energy neutrons from a neutron source to produce Ra-225 and hence Ac-225, which can be used as a generator to produce Bi-213 for use in 'Targeted Alpha Therapy' for cancer. This paper examines the possibility of producing Ac-225 by neutron capture using a theoretical model in which neutron energy is convoluted with the corresponding neutron cross sections of Ra-226. The total integrated yield can then be obtained. This study shows that an intense beam of high-energy neutrons could initiate neutron capture on Ra-226 to produce Ra-225 and hence practical amounts of Ac-225 and a useful reduction of Ra-226.

Production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226.

The increasing application of Ac-225 for cancer therapy indicates the potential need for its increased production and availability. The production of Ac-225 has been achieved using bremsstrahlung photons from an 18 MV medical linear accelerator (linac) to bombard a Ra-226 target. A linac dose of 2800 Gy produced about 64 microCi of Ra-225, which decays to Ac-225. This result, while consistent with the theoretical calculations, is far too low to be of practical use. A more powerful linac is required that runs at a higher current, longer pulse length and higher frequency for practical production. This process could also lead to the reduction of the nuclear waste product Ra-226.

A theoretical model for the production of Ac-225 for cancer therapy by photon-induced transmutation of Ra-226.

Radium needles that were once implanted into tumours as a cancer treatment are now obsolete and constitute a radioactive waste problem, as their half-life is 1600 years. We are investigating the reduction of radium by transmutation on a small scale by bombarding Ra-226 with high-energy photons from a medical linear accelerator (linac) to produce Ra-225, which subsequently decays to Ac-225, which can be used as a generator to produce Bi-213 for use in 'targeted alpha therapy' for cancer. This paper examines the possibility of producing Ac-225 with a linac using an accurate theoretical model in which the bremsstrahlung photon spectrum at 18 MV linac electron energy is convoluted with the corresponding photonuclear cross sections of Ra-226. The total integrated yield can then be obtained and is compared with a computer simulation. This study shows that at 18 MV, the photonuclear reaction on Ra-226 can produce low activities of Ac-225 with a linac. However, a high power linac with high current, pulse length and frequency is needed to produce practical amounts of Ac-225 and a useful reduction of Ra-226.

Line transect sampling in small regions.

This article develops an approach to estimating population abundance from line transect surveys that uses a calibration survey to estimate the detection function, which is then employed as a weight function in constructing the abundance estimate. Nonparametric methods of estimating the detection function via local regression and via a kernel density estimator are considered. The proposed methods are evaluated using a set of Western Australian plant data and weed enumeration data.

Entrance qualifications and student performance in a hybrid problem bases and traditional medical programme

A hybrid problem based learning (PBL) and traditional programme was started at the Trinidad campus of the University of the West Indies in 1989. Analyses were carried out to determine the extent to which the entrance qualifications of the students were related to their performances at the examinations in the Phase I (preclinical and paraclinical) and Phase II (clinical) programmes. Students who were admitted on the basis of their results in the secondary school General Certificate of Examination (GCE), "A" level scored higher at the Phase I, but not at the Phase II, level than those who already had university education. Among the "A" level students, there was positive correlation between the total "A" level scores and the examination marks in the medical programme, particularly at the Phase I level. Futhermore, multiple regression analyses indicated that the grades in "A" level chemistry and, to a lesser extent in biology, had the most influence on performance at the Phase I examinations, with much less influence on performances at the Phase II examinations. These results suggest that good grades at "A" level examination are significant factors, but not the only important ones, that favour high achievement in the initial stages of this type of PBL/traditional medical programme.(AU)

Entrance qualifications and student performance in a hybrid problem based and traditional medical programme

A hybrid problem based learning (PBL) and traditional medical programme was started at the Trinidad campus of the University of the West Indies in 1989. Analyses were carried out to determine the extent to which the entrance qualifications of the students were related to their performances at the examinations in the Phase I (preclinical and paraclinical) and Phase II (clinical) programmes. Students who were admitted on the basis of their results in the secondary school General Certificate of Examination (GCE), 'A' level scored higher at the Phase I, but not at the Phase II, level than those who already had university education. Among the 'A' level students, there was positive correlation between the total 'A' level scores and the examination marks in the medical programme, particularly at the Phase I level. Furthermore, multiple regression analyses indicated that the grades in 'A' level Chemistry and, to a lesser extent in Biology, had the most influence on performances at the Phase I examinations, with much less influence on performances at the Phase II examinations. These results suggest that good grades at 'A' level examinations are significant factors, but not the only important ones, that favour high achievement in the initial stages of this type of PBL/traditional medical programme.

Entrance qualifications and student performance in a hybrid problem based and traditional medical programme.

A hybrid problem based learning (PBL) and traditional medical programme was started at the Trinidad campus of the University of the West Indies in 1989. Analyses were carried out to determine the extent to which the entrance qualifications of the students were related to their performances at the examinations in the Phase I (preclinical and paraclinical) and Phase II (clinical) programmes. Students who were admitted on the basis of their results in the secondary school General Certificate of Examination (GCE), 'A' level scored higher at the Phase I, but not at the Phase II, level than those who already had university education. Among the 'A' level students, there was positive correlation between the total 'A' level scores and the examination marks in the medical programme, particularly at the Phase I level. Furthermore, multiple regression analyses indicated that the grades in 'A' level Chemistry and, to a lesser extent in Biology, had the most influence on performances at the Phase I examinations, with much less influence on performances at the Phase II examinations. These results suggest that good grades at 'A' level examinations are significant factors, but not the only important ones, that favour high achievement in the initial stages of this type of PBL/traditional medical programme.

Changes in the pelagic crustacean zooplankton of high-boreal Island Lake, Saskatchewan, associated with uranium mining.

Island Lake, Saskatchewan, has become eutrophic, subsaline (salinity between 0.5 and 3.0 g I(-1)) and contaminated with several metals over the last decade. In this study, the crustacean zooplankton community in the lake in early summer 1989 is compared to the community during the early summers of the baseline years 1978 and 1979, based on archived environmental impact assessment samples. Community composition has changed, probably because of salinization and perhaps, to a lesser extent, eutrophication. Calanoid copepods have disappeared, while the numbers of species of cyclopoid copepods and cladocerans have increased. Ceriodaphnia reticulata, present in 1988 only, was more numerous than any other species during all three years. Densities of all other species were very low in 1989, which has led to lower diversity (Simpsons Index). Predation by Chaoborus probably contributed to the low abundances in 1989. The characteristics of the zooplankton community in 1989 were very similar to those of zooplankton in culturally acidified lakes, and indicate that Island Lake is in poor health. The success of Ceriodaphnia, a standard toxicity bioassay genus, is noteworthy under such contaminated conditions. While the taxonomic changes are obvious, the zooplankton data are limited; therefore causes can only be inferred. The study demonstrates the need for more and better ecosystem-specific biological information in order to do environmental impact assessments, in this case for mining in the north.

Progress in medical education in the Faculty of Medical Sciences, University of the West Indies: implementation of problem-based learning at the St. Augustine Campus.

This paper reviews some of the developmental procedures regarding changes in Medical Education within the Faculty of Medical Sciences, University of the West Indies. Discussed are some of the constraints experienced in attempting curriculum changes in the established Medical School at Mona, Jamaica, as compared with the implementation of a Problem-based Learning Strategy curriculum at the Eric Williams Medical Complex, St. Augustine, Trinidad and Tobago. At Mona, integration of disciplines, Community-health and other programmes were attempted. However, it was at the Eric Williams Complex, a new school, that the Faculty of Medical Sciences was able to implement a problem-based programme.

Diclofenac hepatitis.

The characteristics of liver damage associated with the use of diclofenac, a popular nonsteroidal anti-inflammatory drug, were investigated by reviewing adverse drug reaction reports for Australia. Twenty six patients were reported for whom diclofenac was the sole suspected drug cause of their liver damage. The average age of the patients was 64 years (range 37-84 years); 19 (70%) were women. The most common clinical features were jaundice, hepatomegaly, anorexia, and nausea. Features of drug hypersensitivity were not reported. Duration of treatment with diclofenac before the onset of the illness ranged from 6-417 days (median 76 days). The most prominent biochemical abnormalities were raised serum aspartate transaminase and alanine transaminase activity of up to 30 to 40 times the upper limit of the normal range. Recovery generally started soon after withdrawal of diclofenac and the decrease in aspartate transaminase and alanine transaminase for the group was exponential, with half lives of around 13 days. The average total dose taken by 18 patients for whom accurate data were available was 8.7 g (range 1.4-63.5 g) and, unexpectedly, there was a significant relation between the logarithm of the dose of diclofenac and the logarithms of the peak and mean transaminase levels. Hepatocellular damage during treatment with diclofenac seems to be a rare event. From this analysis of Australian reports it seems that in a small subgroup of patients liver injury may be a direct toxic effect of diclofenac or a metabolite.

Progress in medical education in the Faculty of Medical Sciences, University of the West Indies: Implementation of problem-based learning at the St Augustine Campus

This paper reviews some of the developmental procedures regarding changes in medical education within the Faculty of Medical Sciences, University of the West Indies. Discussed are some of the constraints experienced in attempting curriculum changes in the established medical school at Mona, Jamaica, as compared with the implementation of a problem-based learning strategy curriculum at the Eric Williams Medical Complex, St Augustine, Trinidad and Tobago. At Mona, integration of disciplines, community-health and other programmes were attempted. However, it was at the Eric Williams Medical Complex, a new school, that the Faculty of Medical Sciences was able to implement a problem-based programme. (AU)

Abnormal thyroid hormone and thyrotropin levels in homozygous sickle cell disease.

Male patients with SS disease had significantly lower T3 and higher TSH levels than a comparison group. Stimulation with TRH in 10 male sibling pairs showed highly significant increases in T3 and TSH in both patients and sibling controls although the increase in TSH was significantly greater in SS disease. The interpretation of these findings is unclear although the thyroid indices indicate an abnormal pituitary-thyroid axis most consistent with a modest primary thyroid failure.

Abnormal thyroid hormone and thyrotropin levels in homozygous sickle cell disease

Male patients with SS disease had significantly lower T3 and higher TSH levels than a comparison group. Stimulation with TRH in 10 male sibling pairs showed highly significant increases in T3 and TSH in both patients and sibling controls although the increase in TSH was significantly greater in SS disease. The interpretation of these findings unclear although the thyroid indices indicate an abnormal pituitary-thyroid axis most consistent with a modest primary thyroid failure

The role of MR and CT in evaluating clival chordomas and chondrosarcomas.

Sixteen chordomas and nine chondrosarcomas of the clivus were evaluated with CT and MR either before (22 cases) or after (three cases) treatment with proton beam irradiation. The ability of these imaging techniques to provide information necessary to direct patient treatment was studied. The tumor was detected and its gross margins were identified by both techniques in all instances. No reliable diagnostic features allowing differentiation between these two tumors were encountered. MR generally was superior in defining the exact position of the brainstem and optic chiasm relative to the tumor, and it frequently provided superior information about tumor extension into the nasopharynx and cavernous sinus. CT was always better than MR in demonstrating tumoral calcification and in defining the exact anatomy of bone destruction. MR was generally superior to CT in demonstrating the position of the cavernous internal carotid artery relative to the tumor and often provided superior visualization of the vertebral and basilar arteries. In cases in which bone-induced artifact obscured the interface between the neural axis and tumor in the CT image, or in which the tumor had suprasellar extension and was likely to compress the optic chiasm and tracts, MR was of great value in planning irradiation therapy. The high occurrence of clinically asymptomatic signal intensity alterations in the MR studies of previously treated patients appears to limit the differential diagnostic value of this information. Given its greater availability and lower cost, CT appears to be the technique of choice for routine follow-up of previously treated patients.

Effects of ackee fruit extracts on bronchomotor tone in rats

The unripe ackee fruit, when eaten, is known to cause serious clinical manifestations, including vomiting, hypoglycaemia and acidosis. The effects, of various extracts from the arilli of the unripe fruit (including hypoglyin-A) on the lungs from rats were examined in an in vitro preparation. All the extracts were found to induce moderately severe broncho-constriction, indicating a possible contribution of these effects to the observed toxicity of ackee (AU)

Effects of ackee fruit extracts on bronchomotor tone in rats

The unripe ackee fruit, when eaten, is known to cause serious clincial manifestations, including vomitting, hypoglycaemia and acidosis. The effects, of various extracts from the arilli of the unripe ackee fruit (including hypoglycin-A) on the lungs from rats were examined in an in vitro preparation. All the extracts were found to induce moderately severe broncho-constriction, indicating a possible contribution of these effects to the observed toxicity of ackee

Testicular function in rats following immobilization stress.

Stress is believed to influence male reproductive activity. Male rats were subjected to immobilization stress for 2 h/day for 30 days to assess the effects of stress on testicular function. Net mass of the testes, epididymes and the seminal vesicles, sperm morphology, number of epididymal sperms and percent progressive motility of the sperms were determined. Adrenal weights were significantly increased (P less than 0.05) in the stressed animals. There was no significant difference between the control and the stressed animals with respect to testicular and epididymal weight, level of sperm production, progressive motility, seminal vesicular weight and abnormal forms. Histological examination also revealed a similarity in the structure of seminiferous tubules, adequacy of cell types of developing germ cells, structure of Leydig cells and epididymal lumina in both the groups. This study demonstrated a lack of significant effect of immobilization stress on testicular function in rats.