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D Young

Publications and source records attributed to D Young.

At least 235 records · Page 13Linked to original sources
PubMed1996

X-ray structure analysis of an engineered Fe-superoxide dismutase Gly-Ala mutant with significantly reduced stability to denaturant.

We have refined the X-ray structure of a site-directed G152A mutant of the iron-dependent superoxide dismutase from Mycobacterium tuberculosis at 2.9 angstroms resolution. The mutation which replaces a glycine residue in a surface loop with alanine was designed to alter the conformation of this loop region which has previously been shown to play a crucial structural role in quaternary interactions within the SOD tetramer. Gly-152 was targeted as it has dihedral angles (phi = 83.1 degrees, psi = -0.3 degrees) close to the left-handed alpha-helical conformation which is rarely adopted by other amino acids except asparagine. Gly-152 was replaced by alanine as it has similar size and polarity, yet has a very low tendency to adopt similar conformations. X-ray data collection on crystals of this mutant at 2.9 angstroms resolution and subsequent least-squares refinement to an R-value of 0.169 clearly establish that the loop conformation is unaffected. Fluorescence studies of guanidine hydrochloride denaturation establish that the mutant is 4 kcal/mol less stable than the wild-type enzyme. Our results indicate that strict conformational constraints imposed upon a region of polypeptide, due for example to interactions with a neighbouring subunit, may force an alanine residue to adopt this sterically hindered conformation with a consequent reduction in stability of the folded conformation.

Alanine↗
PubMed1996

Mammalian CAP interacts with CAP, CAP2, and actin.

We previously identified human CAP, a homolog of the yeast adenylyl cyclase-associated protein. Previous studies suggest that the N-terminal and C-terminal domains of CAP have distinct functions. We have explored the interactions of human CAP with various proteins. First, by performing yeast two-hybrid screens, we have identified peptides from several proteins that interact with the C-terminal and/or the N-terminal domains of human CAP. These peptides include regions derived from CAP and BAT3, a protein with unknown function. We have further shown that MBP fusions with these peptides can associate in vitro with the N-terminal or C-terminal domains of CAP fused to GST. Our observations indicate that CAP contains regions in both the N-terminal and C-terminal domains that are capable of interacting with each other or with themselves. Furthermore, we found that myc-epitope-tagged CAP coimmunoprecipitates with HA-epitope-tagged CAP from either yeast or mammalian cell extracts. Similar results demonstrate that human CAP can also interact with human CAP2. We also show that human CAP interacts with actin, both by the yeast two-hybrid test and by coimmunoprecipitation of epitope-tagged CAP from yeast or mammalian cell extracts. This interaction requires the C-terminal domain of CAP, but not the N-terminal domain. Thus CAP appears to be capable of interacting in vivo with other CAP molecules, CAP2, and actin. We also show that actin co-immunoprecipitates with HA-CAP2 from mammalian cell extracts.

3T3 Cells↗
PubMed1996

Interleukin-12 stimulates B cell growth by inducing IFN-gamma.

Human interleukin-12 (IL-12) is a 70-kDa polypeptide that activates human natural killer cells. It has been purified from the culture supernatant of a human Epstein-Barr virus-transformed B cell line and cloned. We show that native as well as recombinant IL-12 promoted growth of Staphylococcus aureus Cowan I strain (SAC) or anti-mu antibody-activated B cells in a dose-dependent manner. IL-12 also acted in synergy with IL-2 in growth and differentiation of SAC-activated B cells. Since anti-interferon (IFN)-gamma antibody completely abrogates B-cell growth factor (BCGF) activity of IL-12, the BCGF activity is mediated by IFN-gamma. This conclusion is clearly supported by the results that IL-12 indeed induced IFN-gamma production by activated B cells. These results suggest that the B cell proliferative effect of IL-12 may be mediated by autocrine IFN-gamma.

Antigens, CD20↗
PubMed1996

Developmental and genetic influences on the P50 sensory gating phenotype.

Evoked potentials to pairs of click stimuli were recorded from 127 subjects ranging in age from 10 to 39 years to examine the developmental course of auditory sensory gating. The ratio of the amplitude of the second response to that of the first provides a quantitative measure of auditory sensory gating. Contrary to earlier results, the distribution of P50 ratios was unchanged between children and younger adolescents (10-14 years), older adolescents (15-19 years), and adults (20-29 and 30-39 years). Included in the sample were 39 adolescent twins, allowing assessment for possible genetic effects underlying the P50 sensory gating phenotype, by comparison of the similarity of the measure in monozygotic and same-sex dizygotic twin pairs. The monozygotic twins had significantly higher similarity for the P50 ratio within each twin pair than the dizygotic twins. These results are consistent with the presence of genetic influences on the P50 sensory gating phenotype.

Adolescent↗
PubMed1996

A retrospective analysis of laparoscopically assisted ventriculoperitoneal shunts.

BACKGROUND: During the last two years, laparoscopy has been utilized to facilitate the rapid, safe and direct placement of the abdominal component of ventriculoperitoneal shunts. This study was undertaken to review the feasibility, benefits, technique, and clinical application of laparoscopically assisted ventriculoperitoneal (LAVP) shunt placement. METHODS: A retrospective analysis of the records of six patients who underwent LAVP shunt placement was undertaken. The sex, age, technique, indication for surgery, comorbid conditions, complications operative time, results, and mortality were noted. RESULTS: All patients underwent successful shunt placement. This included placement in the face of previous abdominal surgery, including a percutaneous gastrostomy. The one major complication, hemothorax, was not associated with the laparoscopic portion of the procedure. CONCLUSIONS: Using basic laparoscopic skills and nonspecialized equipment, laparoscopic assistance in ventriculoperitoneal shunt placement offers easy, direct placement of the intraabdominal portion of the catheter in most situations and provides definite patient benefits.

Adolescent↗
PubMed1996

Induction of clusterin in the immature brain following a hypoxic-ischemic injury.

A unilateral hypoxic-ischemic (HI) insult in the 21 day old rat has been used to assess the role of clusterin in nerve cell death. Both clusterin mRNA and protein levels were measured at various time points after moderate (15 min) and severe (60 min) HI insult using in situ hybridisation and immunocytochemistry respectively. The severe HI insult lead primarily to necrotic neuronal death and showed very little if any clusterin mRNA and protein induction on the ligated side of the brain. However, following the moderate HI insult there was a dramatic time-dependent accumulation of clusterin protein in neurons of the CA1-CA2 pyramidal cell layers in the hippocampus and cortical layers 3-5, regions undergoing delayed neuronal death. Clusterin mRNA expression, in contrast to neuronal protein accumulation, appeared to be glial in origin (probably astrocytes) with increases in mRNA in and around the hippocampal fissure and only a weak signal over the CA1-CA2 pyramidal cell layer. These results support the hypothesis that the clusterin protein is synthesised in the astrocytes, secreted and then taken up by dying neurons. Clusterin immunoreactivity and in situ DNA end-labelling performed on the same sections revealed that clusterin was accumulating in neurons destined to die by programmed cell death. However the relative time-courses of DNA fragmentation and clusterin immunoreactivity suggest that clusterin production was a result of the selective delayed neuronal death rather than being involved in the biochemical cascade of events that cause it.

Animals↗
PubMed1996

Determinants of hip axis length in women aged 10-89 years: a twin study.

Hip axis length (HAL), a measure of femoral geometry, has been shown to predict hip fracture in white women over the age of 67 years, independently of bone mineral density at the femoral neck. A cross-sectional study of 304 pairs of female twins [176 monozygous (MZ) and 128 dizygous (DZ)], aged between 10 and 89 years, was performed to examine the influence of age, constitutional, lifestyle, and genetic factors on HAL. HAL was calculated from dual energy X-ray absorptiometry scans of the proximal femur using an automated technique with an Hologic QDR-1000W. Lean mass, fat mass, height, and weight were also measured. Maximum mean HAL was achieved by the age of 15 years. After this age there was no discernible dependency of mean HAL on age. Using within-pair differences, after adjusting for height there were no other independent constitutional or lifestyle predictors. Cross-sectionally, after adjustment for height, MZ and DZ correlations were 0.79 (95% CI: 0.73-0.84) and 0.54 (95% CI: 0.39-0.68), respectively, and independent of age. The MZ correlation exceeded the DZ correlation (p < 0.001). The best-fitting model apportioned 79% (SE 7%) of variation in height-adjusted HAL to additive genetic factors. There was marginal evidence that an environmental influence shared by twins explained 31% (SE 16%) of height-adjusted variance (p = 0.07), in which case the genetic variance was reduced to 51% (SE 15%). Adjustment for height had reduced the magnitude of total variance by 26%, and 95% of this reduction was in the additive genetic component. Applying a previously described theoretical model, approximately 10% of the increased risk of hip fracture associated with a maternal history of hip fracture could be attributed to the genetic factors determining HAL. We conclude that, in women, adult HAL is achieved by midadolescence. After adjustment for height, which is itself largely under genetic influence, other genetic factors appear to play the predominant role in explaining variation in HAL.

Adolescent↗
PubMed1996

Pilot study of intraoperative high dose rate brachytherapy for head and neck cancer.

PURPOSE: To develop a new technique, intraoperative high dose rate brachytherapy (IOHDR), to deliver localized radiation therapy intraoperatively to head and neck tumors at sites inaccessible to intraoperative electron beam radiotherapy (IOEBRT) in the skull base region. METHODS: After maximal surgical resection, afterloading catheters spaced 1 cm apart embedded in custom surface applicators made of foam or silicone were placed on resected tumor beds. IOHDR was delivered in a shielded operating room using preplanned dosimetry with a nominal 10 Ci iridium-192 source in an HDR micro-Selectron afterloader. Twenty-nine patients (20 males, 9 females) ranging in age from 9 to 80 years (median = 61) were irradiated intraoperatively for advanced head and neck tumors at sites inaccessible to IOEBRT. Six patients who had previously received external beam radiation (EBRT) ranging from 50 to 75 Gy, were given 15 Gy of IOHDR only. Twenty-three patients who had no prior radiation received 7.5 to 12.5 Gy IOHDR, and 45 to 50 Gy EBRT was planned post-operatively; however, six of these patients did not complete the planned EBRT. Doses to normal tissues were reduced whenever possible by shielding with lead or by displacement with gauze or retractors. Treatment time ranged from 3.8 to 23 min (median = 6.5 min). Five patients received concurrent cis-platinum based chemotherapy. RESULTS: Twenty-nine patients treated to 30 sites had local tumor control of 67% and crade survival of 72%, with the follow-up ranging from 3 to 33 months (median = 21 months). In the group of 17 previously unirradiated patients who had completed full treatment (IOHDR and EBRT) to 18 sites, the local tumor control was 89%, and all of these patients survived. Tumor control in the six previously unirradiated patients who did not complete EBRT was 50% with a crude survival of 50%. In the group of six previously irradiated patients treated by IOHDR only, the local tumor control was 17% with a crude survival of 17%. No intraoperative complications were noted. The delayed morbidity included cerebrospinal fluid (CSF) leak with bone exposure (1), chronic subdural hematoma (1), septicemia (1), otitis media (1), and severe xerostomia (1). We cannot comment on long-term morbidity due to the relatively short follow-up period of 21 months. CONCLUSIONS: It is feasible to deliver IOHDR, with acceptable toxicity, to skull base tumors at sites inaccessible to IOEBRT. The use of IOHDR as a pre-radiotherapy boost produced excellent local control and survival in the selected group of patients who had no previous radiation therapy. The use of exclusive IOHDR in the previously irradiated group resulted in poor outcome, possibly due to the limitations on re-irradiation doses and/or volumes determined by normal tissue tolerance or because these patients have inherently radioresistant tumors. Higher IOHDR doses, additional EBRT, and/or chemotherapy should be considered for this group. The use of IOHDR as a pre-EBRT boost to maximize local control has a promising future in the treatment of carefully selected patients with advanced skull base tumor.

Brachytherapy↗
PubMed1996

Trk receptor alterations in Alzheimer's disease.

The expression of trk receptors in postmortem normal, Huntington's disease and Alzheimer's disease human brains was investigated using immunohistochemistry, in-situ hybridisation and Western blotting. Alzheimer's disease hippocampi displayed an increase in trkA receptor levels in astrocytes in the CA1 region, some of which were associated with beta-amyloid-positive plaques. Truncated trkB receptors were found in high levels in senile plaques, while the full-length receptor was expressed in glial-like cells in the hippocampus of Alzheimer's disease brains. In-situ hybridisation studies indicated that trk receptor mRNA was also elevated in Alzheimer's. The appearance of trkA and trkB receptors in astrocytes and plaques in Alzheimer's disease might be related to beta-amyloid deposition and could be implicated in the development of Alzheimer's disease.

Adult↗
PubMed1996

A retrospective evaluation of the impact of temporomandibular joint arthroscopy on the symptoms of headache, neck pain, shoulder pain, dizziness, and tinnitus.

Forty-three patients who underwent arthroscopic surgery for arthrogenous TMD were polled concerning the effect of surgery on the symptoms of headache, neck pain, shoulder pain, dizziness and tinnitus. Statistically significant levels of symptom reduction were recorded for all symptoms polled. This indicates that a substantial number of significant symptoms are produced by the influence of temporomandibular joint pathology on central neural processes. A model for the affect of temporomandibular joint pathology on cervical and masticatory musculature is proposed. This data implies that we cannot use muscle tenderness, hypertonicity and/or pain to differentiate arthrogenous from myogenous temporomandibular disorders. The characteristics of a population of whiplash onset TMD patients were compared to other TMD populations. The results indicate that whiplash induced TMD may differ from insidious onset TMD and even other trauma onset TMDs by prevalence of neck pain, intensity of neck pain and probability of concurrence of neck pain, shoulder pain, headache and jaw pain. These symptoms resolved within 24 hours of arthroscopic temporomandibular joint surgery indicating that the temporomandibular joint pathology was the perpetuating force behind, if not the cause of, these symptoms.

Accidents, Traffic↗
PubMed1996

Improving patient-doctor concordance: an intervention study in general practice.

OBJECTIVE: This study aimed to examine if providing feedback to the doctor can improve patient-doctor concordance (PDC) on health problems and treatments. METHODS: The study was carried out in a hospital-based primary care service in a lower socioeconomic status (SES) region of metropolitan Melbourne, Australia. A summary of the existing patient-doctor concordance on health problems and treatments was presented to doctors along with a questionnaire seeking their perceptions of and suggestions on how to act on the findings. In a pre- and post-intervention study, data were collected from consecutive new patients who completed a pre- and post-consultation questionnaire seeking information on the presenting complaint, patient-reported health problem, doctor-recorded health problem, treatments received, and patient expectations of and satisfaction with care. Diagnostic data were classified into body systems. Descriptive statistics were obtained and PDC measured. Following the intervention, data collection was repeated to detect any changes in PDC and patient satisfaction. RESULTS: The pre-intervention sample (n = 197) was young (mean age 33 years), evenly divided into English-speaking (48%) and non-English-speaking (52%), and low SES (66%). The post-intervention samples (n = 95) was similar except for a lower proportion of persons from a low SES (27%). Main body systems reported were musculoskeletal, skin, respiratory, digestive, urological and gynaecological. Post-intervention, PDC on health problems improved significantly from 31% to 63% at the problem level (P = 0.001) and from 65% to 79% at the body system level (P = 0.02). PDC on treatments received also improved significantly from 5.5 to 6 out of 7 treatment options (P = 0.003). There were no significant differences due to gender, SES and non-English-speaking background status. CONCLUSION: PDC is a practical, useful and relevant indicator of effective patient-doctor communication. A well-presented summary of existing levels of PDC is an effective intervention to improve PDC and, by inference, patient-doctor communication on health problems and treatments. PDC should also be examined and reported in prevalence and incidence studies based on patient's reports and doctor's records.

Adult↗
PubMed1996

Numerical and structural chromosome aberrations induced by etoposide (VP16) during oocyte maturation of mice: transmission to one-cell zygotes and damage to dictyate oocytes.

The antineoplastic drug etoposide (ET) inhibits topoisomerase II (topo II) activity by forming a ternary complex (DNA-ET-topo II). This complex prevents the DNA-strand-rejoining activity of topo II and may result in structural chromosome aberrations. Inhibition of topo II activity may also predispose cells to aneuploidy because this enzyme is needed for removing regions of DNA catenation prior to chromosome segregation. Our objectives were to study the dose response for ET-induced numerical and structural chromosomal aberrations in mouse one-cell zygotes, to compare these data with those obtained from a contemporary metaphase II (MII) oocyte study and to evaluate the sensitivity of dictyate oocytes to ET-induced aneuploidy. ICR female mice were superovulated and injected i.p. with either 6% dimethylsulphoxide (controls) or 20, 40 or 60 mg/kg ET 2 h after human chorionic gonadotrophin (HCG). ICR males were paired (1:1) with females immediately after treatment. After 17 h the males were removed, and after 24 h the females with a vaginal plug were given colchicine. One-cell zygotes were harvested for cytogenetic analysis 17 h after colchicine. The percentages of hyperploid zygotes were 1.1, 5.7, 13.8 and 20.7 and of zygotes with structural aberrations were 2.5, 16.3, 37.7 and 64.7, for control, 20, 40 and 60 mg/kg ET respectively. The differences between each succeeding dose for both structural and numerical aberrations were statistically significant (P < 0.01). When the ET dose response aneuploidy data from zygotes were compared with similar data from a contemporary study involving metaphase II oocytes, the frequencies of hyperploidy were greater in zygotes than in oocytes. We conclude that when ET is administered during the preovulatory phase of meiosis, it is both an aneugen and a clastogen in mouse one-cell zygotes.

Aneuploidy↗
PubMed1996

Cytogenetic effects of caffeine during in vivo mouse oocyte maturation.

Numerous investigators have studied the reproductive and genetic toxicity of caffeine. Caffeine has also been reported to retard meiotic progression and induce aneuploidy in hamster oocytes in vitro. However, the ability of caffeine to induce aneuploidy in mammalian oocytes in vivo has not been reported. The objective of this study was to test the hypothesis that chemical-induced perturbations during in vivo oocyte meiotic maturation (OM) predispose oocytes to chromosome missegregation. Caffeine inhibits cAMP phosphodiesterase, which is needed for dephosphorylating p34(cdc2) kinase and initiating OM. Following superovulation, a dose of 150 mg/kg caffeine was administered to Institute of Cancer Research (ICR) female mice at various times prior to metaphase I (MI). Ovulated oocytes were collected from the oviducts and processed for cytogenetic analysis. Statistical analyses of the frequencies of hyperploid, MI, diploid, premature centromere separation and single chromatids revealed nonsignificant (P > 0.05) differences between the controls and each of the caffeine groups. Structural chromosome aberrations were not found. Under our experimental conditions, we rejected the hypothesis and concluded that caffeine neither retarded the rate of OM nor increased the incidence of aneuploidy in mouse oocytes. The factors responsible for the different in vivo and in vitro responses require investigation.

Aneuploidy↗
PubMed1996

Visits to medical practitioners in the first 6 months of life.

OBJECTIVE: To assess the use of medical practitioners' services by mothers and their babies in the 6 months following childbirth. METHODOLOGY: Aggregated Medicare data detailing medical practitioner services provided to a random sample of 650 Victorian babies born between 1 March and 31 May 1993 and their mothers were obtained from the Health Insurance Commission. This provided data on services provided between March and December of 1993 to the selected cohort. Services provided by the public hospital system to mothers and babies are not included. RESULTS: Mothers and babies in the sample used 6404 medical practitioner services in the 6 months following birth; 57% of services were to babies, 43% to mothers. Of the 6404 medical practitioner services 5042(79%) were provided by general practitioners (GP), 804(12%) by paediatricians, 319(5%) by obstetricians and 239(4%) by 'other' specialists. The mean number of visits to a GP by mothers was 3.5 and by babies was 4.2 in the 6 months following birth. General practitioners were more likely to be vocationally registered and there were differences in the item numbers charged between those who were vocationally registered and those who were not. The length of GP consultation differed significantly between mothers' and babies' visits. CONCLUSIONS: A previously undocumented level of postnatal use of medical practitioner services is presented. It suggests a significant level of postnatal maternal and infant morbidity that requires further study.

Family Practice↗