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Biomedical subjects

C Nixon

Publications and source records attributed to C Nixon.

At least 19 recordsLinked to original sources
PubMed2006

Evidence for the expression and enzymatic activity of haem oxygenase-1 in the lungs of horses.

The aim of this study was to characterise the expression of haem oxygenase-1 (HO-1) in healthy lung tissue from horses and to measure its activity. Samples of lung tissue were collected from six horses euthanased for reasons other than respiratory disease. HO-1 expression and activity were detected in type II alveolar epithelial cells, macrophages and neutrophils in all the samples examined. The activity was dependent on the presence of NADPH and inhibited quantitatively by the addition of increasing concentrations of a competitive inhibitor of HO-1, tin mesoporphyrin IX.

Animals↗
PubMed2006

Telomerase reverse transcriptase (TERT) expression and proliferation in canine brain tumours.

Telomerase is a ribonucleoprotein enzyme complex that synthesizes telomere DNA. It is detected in 85-90% of malignant tumours in humans, but not in most somatic cells. Because telomerase plays a critical role in cell immortality, it represents an important target for anticancer therapies. We have previously shown that the dog is a potentially useful model for evaluating telomerase-based therapeutics. In this present study we analysed 93 canine brain tumours for telomerase reverse transcriptase (TERT) expression by immunohistochemistry. TERT immunoreactivity was detected in 16 of 50 grade 1 (32%) and 29 of 43 grade 2 tumours (67.4%), demonstrating a statistically significant association with histological grade (P = 0.00012). A subset of 51 tumours was also assessed for MIB-1 expression. The MIB-1 labelling index (LI) was found to correlate significantly with tumour grade, with a mean MIB-1 LI of 1.5% for grade 1 tumours, as compared with a mean MIB-1 LI of 21.7% for grade 2 tumours (P << 0.001). The MIB-1 LI was also significantly associated with TERT expression in all brain tumours (P << 0.001). These data further support the dog as a model for the preclinical development of telomerase-based therapeutics in brain tumours.

Animals↗
PubMed2006

Cohort study of COX-1 and COX-2 expression in canine rectal and bladder tumours.

OBJECTIVES: To determine the role that cyclooxygenase-1 (COX-1) and cyclooxygenase-2 (COX-2) play in malignant transformation in canine transitional cell carcinoma and rectal tumours. METHODS: Histological sections of 21 canine rectal adenocarcinomas and 18 canine transitional cell carcinomas were stained for COX-1 and COX-2. Mann-Whitney non-parametric tests were applied to determine if there was any relationship between the percentage of cells expressing COX-1 or COX-2, and between COX-1 and COX-2 staining intensity and age, breed or sex. RESULTS: For rectal adenocarcinomas, 19.0 per cent of the sections were negative for COX-1 and COX-2. A further 38.1 per cent of the sections were negative for COX-2 but positive for COX-1, and 38.1 per cent of the sections had rare or occasional single cells positive for COX-2. No significant differences were found in COX staining when compared with age, breed or sex. For transitional cell carcinomas, all of the sections were positive for COX-1 and COX-2. For COX-2 staining, 16.7 per cent had more than 30 per cent positive cells. For COX-1 staining, 38.9 per cent had more than 30 per cent positive cells. There was a significant increase in the percentage of COX-1 positive cells in small breed dogs (P = 0.0337). CLINICAL SIGNIFICANCE: The variations in COX expression reported in this study may explain the differences in the clinical response of transitional cell carcinomas and rectal adenocarcinomas following treatment with non-steroidal anti-inflammatory drugs.

Adenocarcinoma↗
PubMed2001

Prevalence of polycystic ovary syndrome (PCOS) in first-degree relatives of patients with PCOS.

OBJECTIVE: To determine the rate of clinically evident polycystic ovary syndrome (PCOS) among first-degree female relatives within families with a proband affected by PCOS. DESIGN: Clinical and biochemical evaluation of the mothers and sisters of 93 patients with PCOS. The diagnosis of PCOS was established by: [1] a history of oligomenorrhea, [2] clinical evidence (i.e., hirsutism) or biochemical evidence (i.e., elevated total or free T) of hyperandrogenism, and [3] the exclusion of related disorders. SETTING: Tertiary care university. PATIENT(S): Patients with PCOS and their mothers and sisters. INTERVENTION(S): Interview, physical examination, and hormonal testing on blood samples were performed for all subjects. MAIN OUTCOME MEASURE(S): The presence of hirsutism and hyperandrogenemia was determined in the mothers and sisters of the patients with PCOS. RESULT(S): Of the 78 mothers and 50 sisters evaluated clinically, 19 (24%) and 16 (32%) were affected with PCOS, respectively. A higher rate of PCOS was observed when only premenopausal women not taking hormones (i.e., untreated) were considered (i.e., 35% of mothers and 40% of sisters), consistent with amelioration of symptoms with hormonal therapy or aging. These rates of PCOS are significantly higher than that observed in our general population (approximately 4%) and suggest the involvement of a major genetic component in the disorder. CONCLUSION(S): The rates of PCOS in mothers and sisters of patients with PCOS were 24% and 32%, respectively, although the risk was higher when considering untreated premenopausal women only.

Adolescent↗
PubMed2000

Proximate humid and dry regions in Jupiter's atmosphere indicate complex local meteorology.

Models of Jupiter's formation and structure predict that its atmosphere is enriched in oxygen, relative to the Sun, and that consequently water clouds should be present globally near the 5-bar pressure level. Past attempts to confirm these predictions have led to contradictory results; in particular, the Galileo probe revealed a very dry atmosphere at the entry site, with no significant clouds at depths exceeding the 2-bar level. Although the entry site was known to be relatively cloud-free, the contrast between the observed local dryness and the expected global wetness was surprising. Here we analyse near-infrared (around 5 microm) observations of Jupiter, a spectral region that can reveal the water vapour abundance and vertical cloud structure in the troposphere. We find that humid and extremely dry regions exist in close proximity, and that some humid regions are spatially correlated with bright convective clouds extending from the deep water clouds to the visible atmosphere.

Atmosphere↗
PubMed1999

Care of minor injuries by emergency nurse practitioners or junior doctors: a randomised controlled trial.

BACKGROUND: We aimed to assess the care and outcome of patients with minor injuries who were managed by a nurse practitioner or a junior doctor in our accident and emergency department. METHODS: 1453 eligible patients, over age 16 years, who presented at our department with minor injuries were randomly assigned care by a nurse practitioner (n=704) or by a junior doctor (n=749). Each patient was first assessed by the nurse practitioner or junior doctor who did a clinical assessment; the assessments were transcribed afterwards to maintain masked conditions. Patients were then assessed by an experienced accident and emergency physician (research registrar) who completed a research assessment, but took no part in the clinical management of the patient. A standard form was used to compare the clinical assessment of the nurse practitioner or junior doctor with the assessment of the research registrar. The primary outcome measure was the adequacy of care (history taking, examination of patient, interpretation of radiographs, treatment decision, advice, and follow-up). FINDINGS: Compared with the rigorous standard of the experienced accident and emergency research registrar, nurse practitioners and junior doctors made clinically important errors in 65 (9.2%) of 704 patients and in 80 (10.7%) of 749 patients, respectively. This difference was not significant. The nurse practitioners were better than junior doctors at recording medical history and fewer patients seen by a nurse practitioner had to seek unplanned follow-up advice about their injury. There were no significant differences between nurse practitioners and junior doctors in the accuracy of examination, adequacy of treatment, planned follow-up, or requests for radiography. Interpretation of radiographs was similar in the two groups. INTERPRETATION: Properly trained accident and emergency nurse practitioners, who work within agreed guidelines can provide care for patients with minor injuries that is equal or in some ways better than that provided by junior doctors.

Adult↗
PubMed1999

The incidence of maternal dental treatment during pregnancy.

A questionnaire was given to women who had delivered a live baby to assess their knowledge and uptake of dental treatment during their recent pregnancy of the 496 women surveyed, 95% knew that dental treatment was free on the National Health Service for 1 year after that pregnancy. Despite a high level of knowledge in this area, 64% underwent a dental check-up during pregnancy and of those women who had a check-up 27% had dental restorations placed in their teeth during that pregnancy. Only 26% of women were advised to see a dentist by a health professional. The exact incidence of dental treatment during pregnancy is not known, however, if our area is typical of the United Kingdom, large numbers of women are undergoing dental treatment during pregnancy and the contribution that this makes to maternal and fetal health should be studied.

Journal Article↗
PubMed1999

Serologic survey for selected infectious disease agents in raccoons from Illinois.

The determination of serologic titers to infectious organisms is a valuable tool for quantitating exposure to disease organisms. Raccoons (Procyon lotor) were live-trapped from September 1989 to October 1993 and samples collected from two distinct locations in west-central Illinois (USA); a state recreational facility (Park) and privately owned farming property (Farm). Sera were submitted for testing Leptospira interrogans (serovars bratislava, canicola, grippotyphosa, hardjo, icterohemmorhagiae, and pomona), canine distemper virus (CDV), pseudorabies virus (PV), and Toxoplasma gondii. Two-hundred and twenty-two (48%) of 459 raccoons were seropositive for L. interrogans. Eighty-five (23%) out of 368 raccoons were seropositive for canine distemper virus. Eighty-two (17%) of 479 raccoons raccoons were seropositive for pseudorabies virus. One hundred and eight-four (49%) of 379 raccoons were seropositive for T. gondii. A significant difference (P < 0.05) in seroprevalence for L. interrogans between the park (43%) and farm (52%) areas was found. A correlation between increasing age and seroprevalence was found for L. interrogans, CDV, PV, and T. gondii. Furthermore, there was a significant difference in seroprevalence for T. gondii during the spring trapping seasons (73%), when compared with the fall (33%). This type of information on exposure to infectious agents is important for developing control programs to manage raccoon-human and raccoon-domestic animals interactions.

Age Distribution↗
PubMed1998

Female voice communications in high level aircraft cockpit noises--part II: vocoder and automatic speech recognition systems.

BACKGROUND: The intelligibility of female and male speech is equivalent under most ordinary living conditions. However, due to small differences between their acoustic speech signals, called speech spectra, one can be more or less intelligible than the other in certain situations such as high levels of noise. Anecdotal information, supported by some empirical observations, suggests that some of the high intensity noise spectra of military aircraft cockpits may degrade the intelligibility of female speech more than that of male speech. METHODS: In an applied research study, the intelligibility of female and male speech was measured in several high level aircraft cockpit noise conditions experienced in military aviation. RESULTS: In Part I, (Nixon CW, et al. Aviat Space Environ Med 1998; 69:675-83) female speech intelligibility measured in the spectra and levels of aircraft cockpit noises and with noise-canceling microphones was lower than that of the male speech in all conditions. However, the differences were small and only those at some of the highest noise levels were significant. Although speech intelligibility of both genders was acceptable during normal cruise noises, improvements are required in most of the highest levels of noise created during maximum aircraft operating conditions. These results are discussed in a Part I technical report. This Part II report examines the intelligibility in the same aircraft cockpit noises of vocoded female and male speech and the accuracy with which female and male speech in some of the cockpit noises were understood by automatic speech recognition systems. The intelligibility of vocoded female speech was generally the same as that of vocoded male speech. No significant differences were measured between the recognition accuracy of male and female speech by the automatic speech recognition systems. The intelligibility of female and male speech was equivalent for these conditions.

Adult↗
PubMed1997

Analysis of the interaction of the human immunodeficiency virus type 1 gp120 envelope glycoprotein with the gp41 transmembrane glycoprotein.

The human immunodeficiency virus type 1 (HIV-1) gp120 exterior envelope glycoprotein interacts with the viral receptor (CD4) and with the gp41 transmembrane envelope glycoprotein. To study the interaction of the gp120 and gp41 envelope glycoproteins, we compared the abilities of anti-gp120 monoclonal antibodies to bind soluble gp120 and a soluble glycoprotein, sgp140, that contains gp120 and gp41 exterior domains. The occlusion or alteration of a subset of gp120 epitopes on the latter molecule allowed the definition of a gp41 "footprint" on the gp120 antibody competition map. The occlusion of these epitopes on the sgp140 glycoprotein was decreased by the binding of soluble CD4. The gp120 epitopes implicated in the interaction with the gp41 ectodomain were disrupted by deletions of the first (C1) and fifth (C5) conserved gp120 regions. These deletions did not affect the integrity of the discontinuous binding sites for CD4 and neutralizing monoclonal antibodies. Thus, the gp41 interface on the HIV-1 gp120 glycoprotein, which elicits nonneutralizing antibodies, can be removed while retaining immunologically desirable gp120 structures.

CD4 Antigens↗
PubMed1997

Femoral artery ligation stimulates capillary growth and limits training-induced increases in oxidative capacity in rats.

OBJECTIVE: The purpose of this study was to assess the interaction of arterial insufficiency and exercise training on soleus and plantaris muscle capillarity and oxidative capacity in adult rats. METHODS: Arterial insufficiency was created by ligation (LIG) of the right femoral artery, and exercise training (TR) was performed on a rodent treadmill. The left hindlimb served as a normally (NORM) perfused control. Capillary:fiber ratio number of capillary contacts per fiber, and citrate synthase activity (CS) were evaluated in the plantaris (Plant) and soleus (Sol) muscles. RESULTS: In sedentary rats, CS was similar between LIG and NORM (Plant: 24.4 vs. 24.3 mumol.min-1.g-1; Sol: 16.6 vs. 16.9 mumol.min-1.g-1), but capillaries per fiber and capillary contacts per fiber were significantly elevated in the plantaris muscle of LIG (2.46 vs. 2.10 caps/fiber, 5.78 vs. 5.03 capillary contacts). CS was elevated in both limbs of TR but was lower in LIG than in NORM (Plant: 28.5 vs. 32.4 mumol.min-1.g-1; Sol: 21.1 vs. 24.9 mumol.min-1.g-1). Treadmill training did not significantly affect capillarity in NORM. However, muscles in the ligated limb of TR tended to have greater capillarity than comparable muscles in either NORM of TR of LIG in SED. CONCLUSIONS: These results demonstrate capillary proliferation in the plantaris but not soleus muscle of rat hindlimbs with femoral artery ligation. Capillarity and CS adaptations were not obligatorily related in LIG, and femoral artery ligation and exercise training appeared to have interactive effects on skeletal muscle capillarity.

Animals↗
PubMed1991

Venous valvular insufficiency: influence of a single venous valve (native and experimental).

This report evaluates the ability of a single competent (native or experimental) superficial femoral vein valve to correct canine hindlimb venous insufficiency. The time to maximal ankle venous pressure after standing (VFT) and to 90% of that time after exercise (VRT90), and the minimal pressure after exercise (AVP) were measured in 17 greyhounds before intervention, after only the superficial femoral vein valve remained (n = 5), and after complete lower limb venous valvulotomy (n = 17). Three weeks later, 12 dogs underwent a native (n = 4) or experimental (n = 8) autogenous venous valve transplantation. Immediately and at 3 weeks after transplantation, venous pressure measurements were obtained. The manual strip test confirmed valve competence at the time of sacrifice. Only one valve transplant became incompetent. Immediately after single superficial femoral vein valve construction, VFT, AVP, and VRT90 measurements were not significantly different from normal. Three weeks after transplantation the AVP measurements were consistent with an insufficient venous system, whereas the VRT90 measurements were between and statistically different from both the control and totally incompetent system (p less than 0.05). After the native valve but not the experimental valve transplantations VFT normalized. These data suggest that insertion of a single competent superficial femoral vein valve into an incompetent lower limb venous system corrects venous pressure measurements initially but soon provides only a partially competent system. The experimental valve, although competent, is less responsive than a native valve.

Animals↗
PubMed1991

The effect of post space preparation on the apical seal of root canal obturated teeth.

The dental literature is contradictory about the quality of the apical seal as it relates to the length of remaining gutta-percha following post-space preparation. The purpose of this study was to compare apical leakage with varying remaining lengths of gutta-percha in an in vitro system. Fifty disarticulated single canal human mandibular premolar teeth were used in five experimental groups. All root canals were prepared 1 mm short of the apical foramen through a size 50 k-file and sequentially flared through a size 70 k-file. Four groups were obturated using gutta-percha with lateral condensation and Roth's 801 Elite Grade root canal sealer. Post-space preparation was accomplished by removing gutta-percha with heated pluggers so that the lengths of the remaining filling varied by increments of one millimeter between 3 and 7 mm. Specimens were covered with enamel paint leaving only the apical foramen exposed. All roots were then submerged in 1 percent methylene blue dye for two weeks, sectioned longitudinally, and measured for depth of dye penetration. No significant difference was found between the 4 and 5 mm groups or between the 6 and 7 mm groups. Significant difference (p less than .05) in leakage did exist between the 3, 4-5, and 6-7 mm groups, showing the least in the latter groups. The best apical seal was obtained when the maximum of 6 mm of gutta-percha remained.

Analysis of Variance↗
PubMed1991

Influences on adolescent mother-infant interactions.

This study investigated the short-term effects of teaching parenting skills to adolescent mothers participating in a specialized school curriculum. It tested the hypothesis that students who are involved in a specialized curriculum will have more positive interactions with their child during feeding and periods of teaching, and will provide a more positive home environment for their child's development. Findings indicated that mothers involved in the specialized curriculum interacted more effectively during time spent teaching their infant than did mothers involved in the traditional school curriculum. The parenting curriculum also influenced teenage mothers to talk with their child during interactions at home, to structure play periods, and to more consciously encourage child development.

Adolescent↗
PubMed1990

Psychomotor recovery after three methods of sedation during spinal anaesthesia.

In a double-blinded study, we have investigated psychomotor recovery after three sedation schemes during spinal anaesthesia for transurethral resection of prostate. Thirty-nine patients were allocated randomly to receive i.v. midazolam only, i.v. midazolam with antagonism by flumazenil or an infusion of propofol. The psychomotor tests were of long and short term memory, critical flicker fusion threshold, attention and concentration, cognition, mental arithmetic, and sedation and anxiety levels, and were performed before operation and at 30 min, 60 min, 2 h and 24 h after operation. Free recall of a picture learning task was the most sensitive test, showing a significant impairment in all groups, persisting for more than 2 h. Propofol was associated with the most rapid recovery and least impairment compared with preoperative baseline. Performance improved in all the tests after antagonism with flumazenil, but was still significantly impaired compared with baseline in tests of picture recall and letter deletion. Significant decreases in performance in all tests were detected 1 h after flumazenil. No increase in anxiety was recorded after flumazenil. We conclude that infusion of propofol is the technique with the most rapid recovery, while only brief and incomplete antagonism of the effects of midazolam may be expected with flumazenil.

Aged↗
PubMed1989

An experimental collagen-impregnated Dacron graft: potential for endothelial seeding.

This study evaluates the potential for endothelial seeding of a collagen-impregnated Dacron graft with or without surface modifiers (fibronectin, heparin) to attach and retain these cells during flow. Human umbilical endothelial cells were harvested, cultured, labeled with Indium111-oxine and seeded onto 30 mm X 4 mm diameter grafts. Six graft surfaces were studied: 1) a collagen-impregnated Dacron graft, HemashieldR (C); 2) C + fibronectin (C + F); 3) C + heparin (C + H); 4) C + F + H; 5) HytrelR + F (Hyt + F); and 6) Hyt + F + H. Radioactive loss determined the percentage attachment and then percentage retention of labeled inoculum after a one-hour in vitro perfusion. Scanning electron and light microscopy demonstrated the endothelium on the graft surface following perfusion. Fibronectin-coated grafts had a significantly higher percentage attachment than those without fibronectin (ANOVA, P less than 0.05). However, the percentage retention following perfusion was similar for all Dacron grafts and statistically inferior to the HytrelR grafts studied (ANOVA, P less than 0.05). SEM evaluation of the C + F + H graft surface was qualitatively the most impressive Dacron surface for seeding, yet was inferior to the HytrelR graft. We conclude that fibronectin benefits the initial attachment of endothelium to collagen-coated Dacron rivaling the HytrelR surface. Fibronectin does not improve percentage retention of the HemashieldR surface during perfusion, therefore, some of its initial benefit is lost.

Blood Vessel Prosthesis↗