PubMed Health⌕ Search

Biomedical subjects

P Buck

Publications and source records attributed to P Buck.

At least 19 recordsLinked to original sources
PubMed2004

Stimulation of microbial sulphate reduction in a constructed wetland: microbiological and geochemical analysis.

Microbial sulphate reduction was stimulated successfully in enclosures installed in a constructed wetland. When sucrose (2.4mM) and NH(4)Cl (600 microM) were added to water in the test enclosures, the indigenous microbial community was able to remove over 90% of the sulphate, present as a contaminant from nearby mining activity at a concentration of 384 mg x l(-1) (4mM), over 50 days. Over 90% of the sucrose was also removed. Sulphate was not reduced in control enclosures containing no added sucrose or NH(4)Cl. Fermentation of sucrose by obligate anaerobes including Clostridium sp. and Bacteriodes sp. preceded sulphate reduction in the test enclosures. Sulphate reduction was biphasic, with maximum rates noted between 2-5 and 23-27 days after the addition of the growth substrates. Relatively unbiased 16S rDNA analysis suggested that nitrogen-fixing bacteria were important constituents of the microbial community in the test enclosures at day 23, suggesting that soluble nitrogen was limiting in the amended test enclosures during the experiment.

Biodegradation, Environmental↗
PubMed2003

Sialolith crystals localized intraglandularly and in the Wharton's duct of the human submandibular gland: an X-ray diffraction analysis.

The exact cause of the formation of sialoliths is unknown. Detailed knowledge of pathogenesis of sialolithiasis and composition of sialoliths is necessary to define new therapeutic procedures. The crystalline components of 23 sialoliths of human submandibular gland were investigated by X-ray powder diffraction analysis. All of the sialoliths localized in the ducts in the submandibular gland consisted of hydroxylapatite. However, in the sialoliths in the Wharton's duct, hydroxylapatite as well as whitlockite and brushite could be found in all except one case. Whitlockite was observed more often in the nucleus of the sialoliths and it was a common co-phase along with hydroxylapatite. The nucleus in one sialolith consisted of brushite and the cortex showed a co-phase of hydroxylapatite and brushite. The occurrence of whitlockite in the sialoliths in Wharton's duct may be due to a higher concentration of calcium and phosphate in saliva in this duct.

Adult↗
PubMed2002

Child health and obstetrics-gynaecology in a problem-based learning curriculum: accepting the limits of integration and the need for differentiation.

BACKGROUND AND OBJECTIVES: The University of Manchester's undergraduate curriculum was reorganised in 1994. Problem-based learning (PBL) was chosen as the central educational method throughout the 5 years. A thematic interdisciplinary style provided a framework around which to select and integrate content. The theme for family, reproductive and child health for the 14-week Families and Children Module (FCM) in year 4 integrated content from obstetrics-gynaecology, paediatrics (including child psychiatry), genetics and public health. This paper focuses on the FCM which has put to test some of the principles of integration. METHODS: The educational process and outcome of the FCM was evaluated with information from (1) Open Forum feedback sessions (2) student questionnaires and (3) students' performance in an objective structured clinical examination (OSCE). RESULTS: Significant problems were encountered during the first year of the FCM (1997--98). An Open Forum for all students and staff was convened after each module in order to address the level of concern. Students' responses to questionnaires reflected the overall impression obtained from the Open Forum. Difficulties appeared to be more than the anxieties and challenges inherent in organisational change and were not simple practical timetabling problems. Tutors perceived a loss of coherence and student contact; students reported difficulties maintaining sufficient continuity of focus in clinical and academic learning experiences. The intended level of integration of paediatrics and obstetrics-gynaecology was unmanageable. Consequently, the FCM (1998-99) was divided into separate attachments for clinical learning and experience in paediatrics and obstetrics-gynaecology, each of 7 weeks' duration. Further open feedback sessions revealed that the modifications implemented in 1998-99 were associated with positive experiences for students and tutors. Comparison of responses to the evaluation questionnaires showed that students' overall rating of the module was higher (P=0.002) for 1998-99 (mean 3.4, SD 0.9) than for 1997-98 (mean 3.0, SD 1.1). CONCLUSIONS: We emphasise that horizontal integration can result in an experience of disintegration for students and tutors. Certain disciplines, such as paediatrics and obstetrics-gynaecology, may not have enough in common for full curriculum integration.

Curriculum↗
PubMed1999

The reproductive performance of sows after PRRS vaccination depends on stage of gestation.

In order to minimize the effects of porcine reproductive and respiratory syndrome (PRRS) on stillbirth, mummification, and neonatal mortality in swine herds, many producers have vaccinated their herds using a modified-live virus vaccine. The purpose of this study was to determine the association of the PRRS modified-live vaccine and reproductive performance by stage of gestation when the vaccine was administered. A total of 47 swine herds from Ontario and Manitoba, Canada, and from the mid-western USA were included in the study. Participating farms had vaccinated all of their sows at one point in time when they used the vaccine for the first time. The reproductive performance of sows that farrowed in the year prior to use of the vaccine was compared to that of sows vaccinated in each of five stages of gestation and in the gestation that followed the initial use of the vaccine. Sows vaccinated at any time during gestation had a reduced number of pigs born alive, a reduced number of pigs weaned per litter, and increased number of stillborn pigs and an increased number of mummified pigs compared to the sows that farrowed prior to use of the vaccine. The largest association was seen in sows that were vaccinated in the last four weeks of gestation. The largest losses were observed in those herds that were vaccinated concurrently with the initial PRRS herd outbreak. These results suggest that the modified-live vaccine should only be administered to non-gestating sows.

Animals↗
PubMed1999

A computerised study on the results of in-vitro-fertilisation.

This project has been concerned with the comparison of children born as a result of fresh embryo transfer (IVF) with children conceived and born via the natural process. The former included children who were the single outcome of the birth (singletons) and children who were the result of a multiple birth (e.g. twins, triplets). A computer database was established into which was put 23 items of data on each child, making a total of 12,788 items overall. There were 278 "normally conceived" children (controls), 150 IVF Singletons, and 128 children from multiple births. The results show interesting differences in the gestational age at birth, the birth weight, the mode of delivery and the degrees of birth abnormalities and malformations.

Birth Weight↗
PubMed1997

Children conceived by in vitro fertilisation after fresh embryo transfer.

AIMS: To compare the outcome in in vitro fertilisation (IVF) children (after fresh embryo transfer) from multiple and singleton births with one another, and with normally conceived control children. METHODS: A cohort of 278 children (150 singletons, 100 twins, 24 triplets and four quadruplets), conceived by IVF after three fresh embryos had been transferred, born between October 1984 and December 1991, and 278 normally conceived control children (all singletons), were followed up for four years after birth. They were assessed for neonatal conditions, minor congenital anomalies, major congenital malformations, cerebral palsy and other disabilities. Control children, all born at term, were matched for age, sex and social class. RESULTS: The ratio of male:female births was 1.03. Forty six per cent of IVF children were from multiple births; 34.9% were from preterm deliveries; and 43.2% weighed less than 2500 g at birth. The IVF singletons were on average born one week earlier than the controls, weighed 400 g less, and had a threefold greater chance of being born by caesarean section. The higher percentage of preterm deliveries was largely due to multiple births and they contributed to neonatal conditions in 45.0% of all IVF children. The types of congenital abnormalities varied: 3.6% of IVF children and 2.5% of controls had minor congenital anomalies, and 2.5% of IVF children and none of the controls had major congenital malformations. The numbers of each specific type of congenital abnormality were small and were not significantly related to multiple births. IVF children (2.1%) and 0.4% of the controls had mild/moderate disabilities. They were all from multiple births, including two children with cerebral palsy who were triplets. CONCLUSIONS: The outcome of IVF treatment leading to multiple births is less satisfactory than that in singletons because of neonatal conditions associated with preterm delivery and disabilities in later childhood. A reduction of multiple pregnancies by limiting the transfer of embryos to two instead of three remains a high priority.

Cerebral Palsy↗
PubMed1995

Vitamin E in macular and peripheral tissues of the human eye.

This study was undertaken to investigate the distribution of vitamin E in the macular and peripheral regions of the human retina, retinal pigment epithelium (RPE) and choroid as a function of age. High-performance liquid chromatography (HPLC) was used to measure alpha- and gamma-tocopherol levels quantitatively using tocol as an internal standard. In 57 out of 70 donor eyes (ages 9-104) the macular region was isolated and the tocopherols analyzed. The conventional brush method and a new vortex method were used to isolate the retinal pigment epithelium cells. Similar trends for the vitamin E levels (increase to the 5th decade, decrease after 7th decade) were found for the macular and peripheral retina and for the macular RPE. In the peripheral RPE a slight continuous increase with age was found. The vitamin E levels are higher in the RPE than in the retina, for both macular and peripheral regions. The amounts of vitamin E/mg protein are lower in the macular retina than in the peripheral retina, whereas in the RPE there is no difference in vitamin E content between macular and peripheral regions. A simple method based on a gentle vortex step was found to offer several advantages over the more generally used isolation of RPE cells based on brushing, and there was no difference in recovery of vitamin E in RPE cells when they were isolated by either isolation technique. It was also found that denominators, used to express the values of vitamin E in tissues should, be used with care since age dependent trends in parameters/denominators could be caused by trends in the denominators only.

Adolescent↗
PubMed1994

A double-blind cross-over controlled study to evaluate the effect of human biosynthetic growth hormone on ovarian stimulation in previous poor responders to in-vitro fertilization.

The effect of exogenous human biosynthetic growth hormone (HGH; 12 IU/day; Norditropin, Novo-Nordisk) on the response to ovarian stimulation using a buserelin/human menopausal gonadotrophin (HMG) regimen was assessed in women who had previously shown a 'poor response' in spite of increasing doses of HMG. Forty patients were recruited into a prospective double-blind placebo-controlled study. The serum follicle stimulating hormone (FSH) on day 2-5 of a menstrual cycle (< 10 IU/l) was used to exclude any peri-menopausal candidates. The urinary 24 h GH secretion was normal in all patients. Thirty-three patients completed the study with 21 patients having human chorionic gonadotrophin (HCG) in both arms, thus providing a complete set of placebo control data. Of these 21 patients, the administration of HGH compared to the placebo cycle resulted in increased serum concentrations of fasting insulin on the 8th (median 3.9 versus 5.8 mU/l; P < 0.0005) and 13th (median 4.4 versus 5.8 mU/l; P < 0.05) day of HMG in those cycles receiving HGH. After 8 days of co-treatment with HGH the number of cohort follicles (14-16.9 mm) was significantly increased, but this change was not sustained on the day of HCG administration. No statistical difference in the serum oestradiol on the 8th day of HMG or day of HCG, length of the follicular phase, total dose of HMG used, or the number of oocytes collected was seen between the placebo or HGH cycles. This study demonstrates that HGH does not improve the ovarian response to ovulation induction in previous poor responders.

Adult↗