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David A Walker

Publications and source records attributed to David A Walker.

12 recordsLinked to original sources
PubMed2026

Inulin, Containing Frutco-Oligosaccharides, and Generalized Anxiety Disorder 7-Item Scale Scores in College Students.

This study was conducted to determine the effects of fructo-oligosaccharide (FOS) inulin on anxiety symptoms in college students. Forty million adults in the United States suffer from anxiety. Previous studies have viewed gut microbiota and its potential link to anxiety in both humans and mice. However, no previous studies focused on the effect of FOS inulin on college students. Fourteen subjects received 4.9 g per day of FOS inulin as the treatment (TX) or no supplement as the control (CON) for 28 days. Both the TX and CON groups were given the Generalized Anxiety Disorder 7-Item Scale (GAD-7) on days 1 and 28. Both groups were also given a 3-day food log at the beginning of the experiment and otherwise maintained their regular diet. Results showed a statistically significant decrease in median GAD-7 scores in both groups (P = .017, r = .637 and P = .042, r = .587 for the TX and CON groups, respectively). However, when comparing the GAD-7 scores between groups, no statistically significant results were found. FOS inulin supplementation did not alleviate anxiety symptoms in college students participating in this study.

Adolescent↗
PubMed2006

Analysis of patients with supratentorial primitive neuro-ectodermal tumours entered into the SIOP/UKCCSG PNET 3 study.

The SIOP PNET 3 study was designed to determine whether 10 weeks of moderately intensive chemotherapy given after surgery and before radiotherapy (RT) would improve the outcome for patients with primitive neuroectodermal tumours (PNETs) compared with RT alone. Patients with a histological diagnosis of supratentorial PNET (StPNET) and no radiological evidence of metastatic disease were initially eligible for randomisation to either chemotherapy followed by craniospinal RT 35 Gy in 21 fractions with a boost of 20 Gy in 12 fractions to the primary site, or RT alone. In respect of the increasing recognition that StPNET were high-risk tumours, randomisation for this group closed in November 1999. This analysis includes both randomised and non-randomised patients with StPNET entered into the study database. Sixty-eight patients aged 2.9-16.6 years (median 6.5 years) were included in the analysis (chemotherapy+RT: 44, RT alone: 24). Fifty-four patients (79%) had a non-pineal and 14 (21%) a pineal site. At a median follow-up of 7.4 years, for all patients overall survival (OS) at 3 and 5 years was 54.4% and 48.3%, respectively. Event-free survival (EFS) at 3 and 5 years was 50.0% and 47.0%, respectively. There was no statistically significant difference in OS or EFS according to treatment received. OS (P=0.05) and EFS (P=0.03) were significantly better for patients with pineal primary sites. EFS for pineal tumours were 92.9% at 3 years and 71.4% at 5 years and for non-pineal primaries 40.7% at 3 years and 40.7% at 5 years. This study confirmed the relatively good survival for non-metastatic pineal PNETs but poor survival of non-pineal StPNETs. There was no evidence that pre-radiation chemotherapy improved outlook. Future treatment programs should be directed at the particular natural history of these tumours, to further define prognostic factors and to explore further biological characteristics.

Adolescent↗
PubMed2005

Outcome for patients with metastatic (M2-3) medulloblastoma treated with SIOP/UKCCSG PNET-3 chemotherapy.

The aim of this study was to determine the outcome for patients with Chang stage M2-3 medulloblastoma (MB) treated with surgery and pre-radiotherapy (RT) chemotherapy (CT). Between 1992 and 2000, 68 patients aged 2.8-16.4 years (median 7.8 years) with M2-3 MB were treated with CT comprising vincristine, etoposide, carboplatin and cyclophosphamide. For 61 patients, CT was followed by craniospinal RT 35 Gy/21 fractions with a posterior fossa (PF) boost, 20 Gy/12 fractions. Twenty-four (35%) irradiated patients received a metastatic boost (mean dose to metastases 47.4 Gy, range 40.0-55.1 Gy). With 7.2-years of median follow-up, overall survival (OS) rates at 3 and 5 years were 50.0% (95% Confidence Interval (CI): 38.1-61.9%) and 43.9% (95% CI: 32.0-55.7%), respectively, event-free survival (EFS) rates at 3 and 5 years were 39.7% (95% CI: 28.1-51.3%) and 34.7% (95% CI: 23.2-46.2%), respectively. Univariate analysis did not demonstrate an impact of age, gender, M stage, extent of resection, RT duration or metastatic boost. For patients commencing RT within 110 days of surgery, EFS was significantly (P=0.04) worse than for those who commenced RT later than this. Response to pre-RT CT was assessable from institutional reports for 44 (65%) patients, and 17 (39%) had a complete response (CR), 15 (34%) a partial response (PR), 4 (9%) stable disease (SD) and 8 (18%) progression. Although CT improved outcome for M0-1 patients in the primitive neuroectodermal tumour (PNET-3) randomised study, and resulted in a high response rate in this study, there has been no apparent improvement in outcome for M2-3 patients when compared with earlier multi-institutional series. Newer approaches such as more intensive CT and RT need to be explored.

Adolescent↗
PubMed2005

Childhood solid tumours: a developmental disorder.

Several lines of evidence demonstrate that the biology, genetics and environment of childhood solid tumours (CSTs) sets them apart from adult solid tumours. The nature of the progenitor cells from which these tumours arise, and their immature tissue environment, allows CSTs to develop with fewer defects in cell regulatory processes than adult cancers. These differences could explain why CSTs are more susceptible to therapeutic intervention than adult tumours. How does the aetiology of these cancers differ from those occurring in adults and how might this affect the development of more effective therapies?

Cell Proliferation↗
PubMed2005

Mandibular distraction osteogenesis for endosseous dental implants.

Patients with complete or partial edentulism who have insufficient bone for endosseous dental implant treatment present a challenge for the dental practitioner. Alveolar distraction osteogenesis is a technique for creating bone and soft tissue, without the need for bone grafting and its potential complications. In this article, alveolar distraction osteogenesis is compared with traditional bone grafting techniques. A case is presented to illustrate successful bilateral mandibular vertical distraction osteogenesis with creation of adequate bone volume for endosseous implant-supported dental restoration.

Alveolar Bone Loss↗
PubMed2004

Impact of radiotherapy parameters on outcome in the International Society of Paediatric Oncology/United Kingdom Children's Cancer Study Group PNET-3 study of preradiotherapy chemotherapy for M0-M1 medulloblastoma.

PURPOSE: To analyze the impact of radiotherapy (RT) parameters on outcome in a randomized study of pre-RT chemotherapy for M0-M1 medulloblastoma. METHODS AND MATERIALS: Patients were randomized to RT alone or RT preceded by chemotherapy with vincristine, etoposide, carboplatin, and cyclophosphamide. RT consisted of craniospinal RT, 35 Gy in 21 fractions, followed by a posterior fossa (PF) boost of 20 Gy in 12 fractions. The accuracy of cribriform fossa, skull base, and PF field placement was assessed. RESULTS: Between 1992 and 2000, 217 patients were randomized, of whom 179 were eligible for analysis. At a median follow-up of 5.4 years, the 3- and 5-year overall survival rate was 79.5% and 70.7%, respectively. The 3- and 5-year event-free survival (EFS) rate was 71.6% and 67.0%, respectively. EFS was significantly better for the chemotherapy plus RT group (3-year EFS rate 78.5% vs. 64.8%, p = 0.0366). Overall survival and EFS were significantly better for patients completing RT within 50 days compared with those taking >50 days to complete RT (3-year overall survival rate 84.1% vs. 70.9%, p = 0.0356, 3-year EFS rate 78.5% vs. 53.7%, p = 0.0092). Multivariate analysis identified the use of chemotherapy (p = 0.0248) and RT duration (p = 0.0100) as predictive of better EFS. Planning films were reviewed for 131 (74.4%) of 176 patients. Sixty-five (49.6%) had no targeting deviations and 58 (44.3%) had one or more deviations. PF recurrence occurred in 11 (34.4%) of 32 with a PF targeting deviation compared with 13 (16.3%) of 80 without (p = 0.043). No statistically significant impact of other targeting deviations on recurrence risk or EFS were found. CONCLUSION: The results of this study have confirmed the importance of the duration of RT for medulloblastoma. Also, attention to detail when planning RT is important, as illustrated in the case of PF field placement.

Adolescent↗
PubMed2004

Ontogeny and nutritional manipulation of the hepatic prolactin-growth hormone-insulin-like growth factor axis in the ovine fetus and in neonate and juvenile sheep.

The somatotrophic axis is the main endocrine system regulating postnatal growth; however, prenatal growth is independent of growth hormone (GH). Fetal development relies on the coordinated actions of a range of hormones, including insulin-like growth factors (IGF), and prolactin (PRL), in the control of differentiation, growth and maturation. In the sheep the abundance peaks for liver IGF-II and PRL receptors occur during late gestation while that for IGF-I receptor occurs at birth. All receptors, with the exception of GH receptor subsequently decrease by age 6 months. It has been proposed that maternal undernutrition during gestation regulates the maturation of the fetal hypothalmic-pituitary-adrenal axis and endocrine sensitivity. Critically, the timing of the nutritional insult may affect the magnitude of reprogramming. Maternal malnutrition during early to mid-gestation (3.2-3.8 MJ/d (60% total metabolisable energy requirements) v. 8.7-9.9 MJ/d (150% total metabolisable energy requirements) between 28 and 80 d of gestation) had no effect on body or liver weight. Nutrient-restricted (NR) fetuses sampled at 80 d (mid-gestation) showed up-regulation of hepatic PRL receptor, but following refeeding the normal gestational rise in PRL and GH receptors did not occur. Hepatic IGF-II receptor was down regulated in NR fetuses at both mid- and late gestation. Conversely, 6-month-old offspring showed no difference in the abundance of either GH receptor or PRL receptor, while IGF-II mRNA was increased. Offspring of ewes malnourished during late gestation (9.1 MJ/d (60% total metabolisable energy requirements) v. 12.7 MJ/d (100% total metabolisable energy requirements) from 110 d of gestation to term) showed reduced abundance of hepatic GH and PRL receptor mRNA. In conclusion, maternal undernutrition during the various stages of gestation reprogrammed the PRL-GH-IGF axis. Nutritional regulation of cytokine receptors may contribute to altered liver function following the onset of GH-dependent growth, which may be important in regulating endocrine adaptations during subsequent periods of nutritional deprivation.

Animal Nutritional Physiological Phenomena↗
PubMed2003

Results of a randomized study of preradiation chemotherapy versus radiotherapy alone for nonmetastatic medulloblastoma: The International Society of Paediatric Oncology/United Kingdom Children's Cancer Study Group PNET-3 Study.

PURPOSE: To determine whether preradiotherapy (RT) chemotherapy would improve outcome for Chang stage M0-1 medulloblastoma when compared with RT alone. Chemotherapy comprised vincristine 1.5 mg/m2 weekly for 10 weeks and four cycles of etoposide 100 mg/m2 daily for 3 days, and carboplatin 500 mg/m2 daily for 2 days alternating with cyclophosphamide 1.5 g/m2. PATIENTS AND METHODS: Patients aged 3 to 16 years inclusive were randomly assigned to receive 35 Gy craniospinal RT with a 20 Gy posterior fossa boost, or chemotherapy followed by RT. RESULTS: Of 217 patients randomly assigned to treatment, 179 were eligible for analysis (chemotherapy + RT, 90 patients; RT alone, 89 patients). Median age was 7.67 years, and median follow-up was 5.40 years. Overall survival (OS) at 3 and 5 years was 79.5% and 70.7%, respectively. Event-free survival (EFS) at 3 and 5 years was 71.6% and 67.0%, respectively. EFS was significantly better for chemotherapy and RT (P =.0366), with EFS of 78.5% at 3 years and 74.2% at 5 years compared with 64.8% at 3 years and 59.8% at 5 years for RT alone. There was no statistically significant difference in 3-year and 5-year OS between the two arms (P =.0928). Multivariate analysis identified use of chemotherapy (P =.0248) and time to complete RT (P =.0100) as having significant effect on EFS. CONCLUSION: This is the first large multicenter randomized study to demonstrate improved EFS for chemotherapy compared with RT alone. It is anticipated that this regimen could reduce ototoxicity and nephrotoxicity compared with cisplatin-containing schedules. The importance of avoiding interruptions to RT has been confirmed.

Adolescent↗