PubMed Health⌕ Search

Biomedical subjects

N Mason

Publications and source records attributed to N Mason.

At least 19 recordsLinked to original sources
PubMed2006

Incidence and risk factors for hip or other bone fractures among hemodialysis patients in the Dialysis Outcomes and Practice Patterns Study.

The available data on bone fractures in hemodialysis (HD) patients are limited to results of a few studies of subgroups of patients in the United States. This study describes the prevalence of hip fractures and the incidence and risk factors associated with hip and other fractures in representative groups of HD facilities (n=320) and patients (n=12 782) from the 12 countries in the second phase of the Dialysis Outcomes and Practice Patterns Study (2002-2004). Among prevalent patients, 2.6% had a prior hip fracture. The incidence of fractures was 8.9 per 1000 patient years for new hip fractures and 25.6 per 1000 for any new fracture. Older age (relative risk (RR)(HIP)=1.91, RR(ANY)=1.33, P<0.0001), female sex (RR(HIP)=1.41, P=0.02; RR(ANY)=1.59, P<0.0001), prior kidney transplant (RR(HIP)=2.35, P=0.04; RR(ANY)=1.76, P=0.007), and low serum albumin (RR(HIP)=1.85, RR(ANY)=1.45, per 1 g/dl lower, P<0.0001) were predictive of new fractures. Elevated risk of new hip fracture was observed for selective serotonin reuptake inhibitors and combination narcotic medications (RR=1.63, RR=1.74, respectively, P<0.05). Several medications were associated with risk of any new fracture: narcotic pain medications (RR=1.67, P=0.02), benzodiazepines (RR=1.31, P=0.03), adrenal cortical steroids (RR=1.40, P<0.05), and combination narcotic medications (RR=1.72, P=0.001). Parathyroid hormone (PTH) levels >900 pg/ml were associated with an elevated risk of any new fracture (RR=1.72, P<0.05) versus PTH 150-300. The results suggest that greater selectivity in prescribing several classes of psychoactive drugs and more efficient treatment of secondary hyperparathyroidism may help reduce the burden of fractures in HD patients.

Adolescent↗
PubMed2005

Anomalous conductance quantization in carbon nanotubes.

Conductance measurements of carbon nanotubes containing gated local depletion regions exhibit plateaus as a function of gate voltage, spaced by approximately 1e(2)/h, the quantum of conductance for a single (nondegenerate) mode. Plateau structure is investigated as a function of bias voltage, temperature, and magnetic field. We speculate on the origin of this surprising quantization, which appears to lack band and spin degeneracy.

Journal Article↗
PubMed2005

Gate-defined quantum dots on carbon nanotubes.

We report the realization of nanotube-based multiple quantum dots that are fully defined and controlled with electrostatic gates. Metallic top-gates are used to produce localized depletion regions in the underlying tubes; a pair of such depletion regions in a nanotube with ohmic contact electrodes defines the quantum dot. Top-gate voltages tune the transparencies of tunnel barriers as well as the electrostatic energies within single and multiple dots. This approach allows precise control over multiple devices on a single tube, and serves as a design paradigm for nanotube-based electronics and quantum systems.

Crystallization↗
PubMed2004

Local gate control of a carbon nanotube double quantum dot.

We have measured carbon nanotube quantum dots with multiple electrostatic gates and used the resulting enhanced control to investigate a nanotube double quantum dot. Transport measurements reveal honeycomb charge stability diagrams as a function of two nearly independent gate voltages. The device can be tuned from weak to strong interdot tunnel-coupling regimes, and the transparency of the leads can be controlled independently. We extract values of energy-level spacings, capacitances, and interaction energies for this system. This ability to control electron interactions in the quantum regime in a molecular conductor is important for applications such as quantum computation.

Journal Article↗
PubMed2001

Evidence of progesterone receptors in the mucosa of the urinary bladder.

OBJECTIVE: To investigate whether progesterone receptors are present in the mucosa of the urinary bladder of continent premenopausal women compared with continent postmenopausal women. MATERIALS AND METHODS: Fifty-seven biopsies from the mucosa of the trigone and lateral wall of the urinary bladder were examined by the avidin-biotin-peroxidase immunohistochemical technique for the presence of estrogen and progesterone receptors. The specimens were obtained at cystoscopy performed to investigate hematuria in 42 patients and neoplasia in 15. The study group (n = 29) comprised non-pregnant premenopausal women in the luteal phase of their menstrual cycle and the control group (n = 28) comprised postmenopausal women. None of the subjects had urinary incontinence or was taking medication with hormones. In no case did the primary lesion involve the specimen used for laboratory analysis. RESULTS: There was positive immunostaining with estrogen in 28 patients of the study group (96.5%) and 4 (14.4%) in the control group (p<0.0001). The 28 samples of the study group also showed positive immunostaining for progesterone receptors. There was positive immunostaining with progesterone in 18 samples (64.3%) of the control group (p<0.01). Fourteen samples (50%) of the control group thus showed positive immunostaining for progesterone but no evidence of positive immunostaining with estrogen. Immunostaining for estrogen and progesterone receptors was similar in trigonal and lateral wall samples. CONCLUSION: In continent pre- and post-menopausal women, a direct progestogenic effect on the mucosa of the urinary bladder seems likely in addition to estrogen.

Adolescent↗
PubMed2001

Pattern of malignant lymphoma in the United Arab Emirates--a histopathologic and immunologic study in 208 native patients.

The aim of this study was to analyze the distribution of the various pathologic types of lymphoma in a native Arab population of the United Arab Emirates (UAE). Two hundred and eight patients with malignant lymphoma diagnosed over a 12-year period (1988-1999) were retrospectively studied morphologically and immunohistochemically with a panel of monoclonal antibodies and classified according to the revised European-American classification of lymphoid neoplasms (REAL). Of the 208 patients in the study, 41% had Hodgkin's disease (HD) and 59% had non-Hodgkin's lymphoma (NHL). The distribution of HD showed a predominance of nodular sclerosis and mixed cellularity types. Among NHLs, the most frequent type was diffuse large B cell (59% of all NHLs) followed by the Burkitt's type (13%). The proportion of primary extranodal NHL was 29%. Immunologically, the percentages of NHL with B-cell and T-cell phenotypes were 83 and 11, respectively. When the International Working Formulation was used, 34% of NHLs were classified as high grade, 59% as intermediate grade and only 7% as low-grade lymphomas.

Adolescent↗
PubMed2001

Intrathecal sufentanil and morphine for post-thoracotomy pain relief.

In this double-blind randomized study we compared a group of 15 patients undergoing thoracotomy who received a spinal injection of sufentanil 20 microg combined with morphine (200 microg) after induction of general anaesthesia with a control group of the same size. Post-operative pain was rated on a visual analogue scale (VAS) and a verbal rating scale at rest and with a VAS on coughing. In the recovery room, patients received titrated i.v. morphine until the VAS score was <30, and were followed by patient-controlled analgesia (PCA) for 72 h. The intrathecal sufentanil and morphine group had a lower intra-operative requirement for i.v. sufentanil and needed less i.v. morphine for titration in the recovery room. I.v. PCA morphine consumption and pain scores were lower in the active group than in the control group during the first 24 h. There were no differences after this time. Spirometric data (peak expiratory flow, forced vital capacity and forced expiratory volume in 1 s) were similar in the two groups. We conclude that the combination of intrathecal sufentanil and morphine produces analgesia of rapid onset and with a duration of 24 h.

Adult↗
PubMed2001

Photodynamic therapy in the canine prostate using motexafin lutetium.

Our purpose was to determine the feasibility of comprehensive treatment of the canine prostate with photodynamic therapy (PDT) using motexafin lutetium (Lu-Tex) and to evaluate the toxicity and tissue effects associated with this treatment. Twenty-five adult male beagles with normal prostate glands were given an i.v. injection of the second-generation photosensitizer Lu-Tex (2-6 mg/kg). An additional two dogs were used as controls and did not receive any photosensitizing drug. All 27 dogs underwent laparotomy to expose the prostate. Three hours postinjection, a total dose of 75-150 J/cm of 732 nm laser light was delivered interstitially and/or transurethrally to the prostate via cylindrical diffusing fibers. Dogs were euthanized between 2 days and 3 months after PDT. All subjects were monitored for clinical evidence of toxicity. Specimens were examined macroscopically and microscopically to characterize the tissue reaction and assess extent of tissue effect as a result of treatment. Interstitial and/or transurethral PDT were successfully delivered in all dogs with no perioperative complications. No clinical evidence of acute urinary obstruction or rectal bleeding was noted. At all dose levels, macroscopic and microscopic evaluation revealed a prostatic tissue reaction characterized initially (within 48 h) by inflammation and necrosis followed by fibrosis and glandular epithelial atrophy. Comprehensive treatment of the entire prostate could be achieved using the interstitial alone approach or combined transurethral and interstitial approach. The transurethral alone approach did not result in complete coverage of the prostate. Dogs receiving transurethral or combined interstitial and transurethral treatment developed erythema and urethral epithelial disruption at all dose levels. Those receiving combined treatment at the highest dose level (Lu-Tex 6 mg/kg, 150 J/cm light) developed urethral fistulae and peritonitis. Dogs treated with the interstitial alone approach were found to have the least amount of urethral damage. Comprehensive treatment of the canine prostate with Lu-Tex PDT is feasible using an interstitial alone or combined interstitial and transurethral approach. The interstitial alone technique results in the least amount of toxicity. The prostatic tissue reaction to treatment is characterized by initial inflammation and necrosis followed by fibrosis and glandular epithelial atrophy.

Animals↗
PubMed2000

Elongation arrest is a physiologically important function of signal recognition particle.

Signal recognition particle (SRP) targets proteins for co-translational insertion through or into the endoplasmic reticulum membrane. Mammalian SRP slows nascent chain elongation by the ribosome during targeting in vitro. This 'elongation arrest' activity requires the SRP9/14 subunit of the particle and interactions of the C-terminus of SRP14. We have purified SRP from Saccharomyces cerevisiae and demonstrated that it too has elongation arrest activity. A yeast SRP containing Srp14p truncated at its C-terminus (delta C29) did not maintain elongation arrest, was substantially deficient in promoting translocation and interfered with targeting by wild-type SRP. In vivo, this mutation conferred a constitutive defect in the coupling of protein translation and translocation and temperature-sensitive growth, but only a slight defect in protein translocation. In combination, these data indicate that the primary defect in SRP delta C29 is in elongation arrest, and that this is a physiologically important and conserved function of eukaryotic SRP.

Biological Transport↗
PubMed2000

Intestinal helminths of spiny mice (Acomys cahirinus dimidiatus) from St Katherine's Protectorate in the Sinai, Egypt.

Spiny mice, Acomys cahirinus dimidiatus, inhabiting the wadis close to St Katherine in the mountains of the Sinai peninsula, were trapped and their helminth parasites were studied. Sixty one mice provided faeces for analysis and 27 were killed and autopsied. Six species of helminths were recorded (the spirurid nematodes, Protospirura muricola (74.1%) and Mastophorus muris (11.1%), the oxyuroid nematodes, Dentostomella kuntzi (59.3%), Aspiculuris africana (3.7%), and Syphacia minuta (3.7%) and the hymenolepidid cestode Rodentolepis negevi (18.5%)). The spirurids were the dominant species present, accounting for up to 0.87% of total host body weight. Analysis of worm weights and lengths suggested that transmission had been taking place in the months preceding our study. No sex difference in the prevalence or abundance of spirurids was detected. Significant differences were identified in the abundance of total nematode burdens and the mean helminth species richness between the three wadis which provided multiple captures of mice. There was also a marked effect of host age on both parameters. A highly significant positive correlation between spirurid egg counts and total worm biomass indicated that non-invasive techniques based on egg counts could be used to quantify worm burdens and when this technique was applied to a larger sample size (n = 61), a significant difference between sites but no host sex or age effects were detected for spirurid faecal egg counts. The data suggest that there are differences between helminth component communities infecting spiny mice in different neighbouring wadis, a hypothesis which will be explored further through our continuing studies in the Sinai.

Age Factors↗
PubMed1998

Non-evidence of estrogen receptors in the rectal mucosa.

The aim of the study was to investigate whether estrogen receptors are present in the rectal mucosa of premenopausal women compared to postmenopausal women and men. Thirty biopsies obtained from the rectal mucosa at colonoscopy, performed to investigate inflammatory bowel disease in 23 patients and neoplasia in 7, were examined by the avidin-biotin-peroxidase immunohistochemical technique for the presence of estrogen receptors. The study group (n = 10) were non-pregnant premenopausal women and the control group (n = 20) were postmenopausal women (n = 10) and men (n = 10). None of the subjects had fecal incontinence or was taking medication with hormones. In no case did the primary lesion involve the specimen used for laboratory analysis. All samples showed negative immunostaining for estrogen receptors. It was concluded that in continent women and men, a direct estrogenic effect on the rectal mucosa seems unlikely.

Adult↗
PubMed1998

Assessment of pelvic stabilization devices for improved field reproducibility.

The aim of this study was to evaluate the improvement in patient comfort and field positional accuracy provided by a new pelvic stabilization system when delivering multiple field radiotherapy to the pelvis. The Pelvic Cradle (BEHTS Manufacturing, Brisbane, Qld, Australia) is a stabilization device that provides reproducible patient positioning and levelling. Ninety patients were randomized into three groups. The first group was treated using the Pelvic Cradle, the second group was treated using current stabilization practices, and the third group was treated using the Pron Pillo (Chattanooga Pharmacal Company, USA) and current stabilization practices. Port films were assessed for field displacement in the lateral and cranio-caudal directions. A patient survey was used to evaluate the patient's perception of comfort while receiving treatment. When compared to the control group, the pelvic cradle group demonstrated a 48% improvement in the mean lateral deviation from 3.8 mm to 2.0 mm (P < 0.001) and a 36% improvement in the mean cranio-caudal deviation from 3.9 mm to 2.5 mm (P < 0.001). The Pelvic Cradle was found to provide an improved level of field positional accuracy while maintaining patient comfort.

Aged↗
PubMed1994

Sera from habitual aborters induce monocyte procoagulant activity: a lymphocyte-dependent event.

Placental thrombosis is a prominent feature in patients with unexplained recurrent fetal loss. To determine whether induction of monocyte procoagulant activity might be a relevant mechanism for unexplained recurrent fetal loss, peripheral blood mononuclear cells isolated from normal healthy controls were cocultured with (a) sera from normal healthy controls (n = 16), (b) sera from habitual aborters (n = 41), and (c) lipopolysaccharide as a positive control. Sera from three patients were fractionated on Sephracryl S-300 and the inducing molecule(s) characterized. Sera from normal healthy controls failed to induce procoagulant activity above basal levels of 21 +/- 4.6 mU/10(5) peripheral blood mononuclear cells. Of the sera from 41 habitual aborters examined 26 (63%) induced procoagulant to a mean value of 410 +/- 48 mU/10(5) peripheral blood mononuclear cells (P < 0.01). Sera from 15 patients failed to augment procoagulant activity. The induction of procoagulant activity was maximal after 6 hr of incubation and was lymphocyte dependent. Fractionation of serum from the three patients on Sepharcryl S300 revealed the procoagulant activity (PCA)-inducing factor(s) to have a molecular weight of between 300,000 and 800,000 Da. The serum factor was found to be heat, alkaline, and acid sensitive. Both anti-IgM and anti-IgA immunoabsorbents reduced the PCA-inducing factor. We conclude that IgM and IgA from some patients with unexplained recurrent fetal loss are capable of inducing procoagulant activity and could contribute to the development of placental microthrombi and infarction, prominent features of this syndrome.

Abortion, Habitual↗
PubMed1991

School-aged children with phonologic disorders: coexistence with other speech/language disorders.

Subjects in grades 1-12 with phonologic disorders were identified and categorized into either Residual or Delayed groups. Group selection was based on a subject rating system of communicative defectiveness and number and type of phonologic errors. The subjects' performance was compared with that of normal individuals on a number of speech and language parameters. The results indicated that voice disorders, deficits in expressive language, and hearing problems occurred in persons exhibiting phonologic disorders with a higher frequency than in the normal individuals.

Adolescent↗