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Biomedical subjects

M Dixon

Publications and source records attributed to M Dixon.

At least 55 records · Page 3Linked to original sources
PubMed1999

Iliac vascular injuries during elective laparoscopic surgery.

Although it is extremely uncommon, iliac vascular injury is a serious complication of laparoscopic surgery. We performed a retrospective review of five patients who sustained injury to the iliac vessels during elective laparoscopic surgery. We reviewed the mechanism and location of injury for each case and examined ways in which such complications can be prevented. There were four women and one man; their mean age was 32 years. Three patients were undergoing laparoscopy at our institution, and two patients were transferred from outlying facilities soon after the injuries occurred. There were a total of seven iliac vascular injuries among our five patients. Three cases involved injury caused by the insufflation needle; the other two were injured by trocar introduction. Postoperative sequelae included decreased lower-extremity pulses in two patients and lower-extremity edema in three patients. The incidence of iliac vascular injury can be significantly reduced by proper insertion technique, the use of an open (Hasson) approach rather than the percutaneous insufflation needle, and a thorough knowledge of the vascular anatomy in the pelvic region.

Adult↗
PubMed1999

Serum antibody response to oral infection precedes but does not prevent Porphyromonas gingivalis-induced alveolar bone loss in mice.

The purpose of this study was to determine whether humoral immunity prevents bacterially induced alveolar bone loss. BALB/cByJ mice were orally infected with the human periodontopathic bacterium Porphyromonas gingivalis, and were compared with sham-infected mice. Specific serum antibody titers to P. gingivalis were measured by enzyme-linked immunosorbent assay. Alveolar bone levels were measured as the distance from the cementoenamel junction to the alveolar bone crest and bone loss was defined as a change in bone levels over time or between infected and sham-infected animals. The specific humoral response was predominantly of the IgG isotype, although low levels of specific serum IgA were also present. Antibody titers in the infected animals were significantly different from those in the sham-infected animals by 18 days and remained at maximal levels at 47 days. Bone loss became significant by 26 days and continued to progress at 47 days. Thus the serum antibody response to oral infection with P. gingivalis preceded detectable bone loss and remained elevated while bone loss increased. The presence of specific antibody did not prevent the onset or progression of bone loss.

Alveolar Bone Loss↗
PubMed1999

Inferring sublexical correspondences from sight vocabulary: evidence from 6- and 7-year-olds.

We report an experiment designed to investigate 6-to-7-year-old children's ability to acquire knowledge of sublexical correspondences between print and sound from their reading experience. A computer database containing the printed word vocabulary of children taking part in the experiment was compiled and used to devise stimuli controlled for grapheme-phoneme correspondence (GPC) frequency and rime neighbourhood consistency according to the children's reading experience. Knowledge of GPC rules and rime units was compared by asking children to read aloud three types of nonword varying in regularity of GPC and consistency of rime pronunciation. Results supported the view that children can acquire knowledge of both GPC rules and rime units from their reading experience. GPC rule strength affects the likelihood of a GPC response; rime consistency affects the likelihood of a rime response.

Analysis of Variance↗
PubMed1999

EYA4, a novel vertebrate gene related to Drosophila eyes absent.

We have isolated a family of four vertebrate genes homologous to eyes absent (eya), a key regulator of ocular development in Drosophila. Here we present the detailed characterization of the EYA4 gene in human and mouse. EYA4 encodes a 640 amino acid protein containing a highly conserved C-terminal domain of 271 amino acids which in Drosophila eya is known to mediate developmentally important protein-protein interactions. Human EYA4 maps to 6q23 and mouse Eya4 maps to the predicted homology region near the centromere of chromosome 10. In the developing mouse embryo, Eya4 is expressed primarily in the craniofacial mesenchyme, the dermamyotome and the limb. On the basis of map position and expression pattern, EYA4 is a candidate for oculo-dento-digital (ODD) syndrome, but no EYA4 mutations were found in a panel of ODD patients.

Alternative Splicing↗
PubMed1999

CD4(+) T cells and the proinflammatory cytokines gamma interferon and interleukin-6 contribute to alveolar bone loss in mice.

In this study, we used a mouse model to examine the role of the adaptive immune response in alveolar bone loss induced by oral infection with the human gram-negative anaerobic bacterium Porphyromonas gingivalis. Severe combined immunodeficient mice, which lack B and T lymphocytes, exhibited considerably less bone loss than did immunocompetent mice after oral infection, suggesting that lymphocytes contribute to this process. Bone loss after oral infection was decreased in mice deficient in major histocompatibility complex (MHC) class II-responsive CD4(+) T cells, but no change in bone loss was observed in mice deficient in MHC class I-responsive CD8(+) T cells or NK1(+) T cells. Mice lacking the cytokine gamma interferon or interleukin-6 also demonstrated decreased bone loss. These results suggest that the adaptive immune response, and in particular CD4(+) T cells and the proinflammatory cytokines that they secrete, are important effectors of bone loss consequent to P. gingivalis oral infection. The studies also reinforce the utility of the mouse oral infection model in dissecting the pathobiology of periodontal disease.

Adaptation, Physiological↗
PubMed1999

Choice of management strategy for colorectal cancer based on a diagnostic immunohistochemical test for defective mismatch repair.

BACKGROUND: Despite intensive research into the molecular abnormalities associated with colorectal cancer (CRC), no diagnostic tests have emerged which usefully complement standard histopathological assessments. AIMS: To assess the feasibility of using immunohistochemistry to detect replication error (RER) positive CRCs and determine the incidence of RER positivity within distinct patient subgroups. METHODS: 502 CRCs were analysed for RER positivity (at least two markers affected) and/or expression of hMSH2 and hMLH1. RESULTS: There were 15/30 (50%) patients with metachronous CRCs, 16/51 (31%) with synchronous CRCs, 14/45 (31%) with a proximal colon carcinoma, and 4/23 (17%) who developed a CRC under the age of 50 showed RER positivity. However, 0/54 patients who developed a solitary carcinoma of the rectum/left colon over the age of 50 showed RER positivity. Immunohistochemical analysis revealed that 66/66 (100%) RER positive carcinomas were associated with complete lack of expression of either hMSH2 or hMLH1. This correlation was confirmed using a further 101 proximal colon carcinomas. Patients with a mismatch repair defective carcinoma showed improved survival but a 5.54 times relative risk of developing a metachronous CRC. A prospective immunohistochemical study revealed 13/117 (11%) patients had a mismatch repair defective carcinoma. A fivefold excess of hMLH1 defective cases was noted. CONCLUSIONS: All RER positive carcinomas were identified by the immunohistochemical test. This is the first simple laboratory test which can be performed routinely on all CRCs. It will provide a method for selecting patients who should be investigated for HNPCC, offered long term follow up, and who may not respond to standard chemotherapy regimens.

Adaptor Proteins, Signal Transducing↗
PubMed1998

Serotonin neuronal release from dorsal hippocampus following electrical stimulation of the dorsal and median raphé nuclei in conscious rats.

We have studied 5-hydroxytryptamine (5-HT) release in the hippocampal formation following electrical stimulation of the dorsal and median raphé nuclei in the behaving rat. The primary finding in this study is a decrease in neuronal release of serotonin in the dorsal hippocampal formation following electrical stimulation of either the dorsal or median raphé nucleus in conscious rats. At no time did electrical stimulation of either raphé nucleus result in behavioral, including vigilance state, changes. The amount of 5-HT released was found to be frequency dependent with higher frequencies (20 Hz) producing larger decreases in release of 5-HT. However, the pattern of release differs between the two raphé nuclei. Extracellular levels of 5-HT decrease during stimulation of the dorsal raphé, whereas levels decrease only following cessation of stimulation of the median raphé nucleus. This may relate to the patterns of innervation of the dorsal hippocampal formation by these two midbrain raphé nuclei and also may reflect an inhibition of median raphé cell firing during stimulation of the dorsal raphé. Electrical stimulation of the dorsal raphé in anesthetized animals resulted in an enhanced release of 5-HT. The suppression of 5-HT release in the dorsal hippocampal formation in behaving animals was long-lasting (over 2 h), suggesting that the control mechanisms that regulate 5-HT release operate over a long time-course. This difference in release between non-anesthetized and anesthetized animals may relate to anesthesia blocking long- and/or short-loop serotonin recurrent axonal collaterals negatively feeding back onto 5-HT1A and 5-HT1D somatodendritic autoreceptors on raphé neurons. Further, the anesthetized animal has diminished monoaminergic "gating" influences on the hippocampal formation, whereas the behaving animal is more complex with behavioral (vigilance) states associated with different patterns of gating of information flow through the hippocampal formation.

Animals↗
PubMed1998

Initial clinical trial and pharmacokinetics of Thymitaq (AG337) by 10-day continuous infusion in patients with advanced solid tumors.

PURPOSE: To establish the maximum tolerated dose (MTD), dose-limiting and other major toxicities and the major pharmacokinetic parameters of a 10-day infusion of the nonclassical antifolate Thymitaq. METHODS: The drug was given by 10-day infusion via a portable pump. The starting dose was 286 mg/m2 per day with escalation to 572 and 716 mg/m2 per day. Thymitaq in plasma was assayed by a validated isocratic reverse-phase HPLC assay with detection at 273 nm. RESULTS: The dose of 716 mg/m2 per day x 10 was considered too high as none of three patients completed a 10-day infusion and two of three developed grade IV myelotoxicity. At 572 mg/m2 per day three of four patients completed a 10-day infusion. Dose-limiting myelosuppression was seen in one of four but owing to a high incidence of thrombotic phenomena, no further patients were added. CONCLUSION: Continuous 10-day infusions of Thymitaq should be limited to low doses until further studies can be done.

Adult↗
PubMed1998

Combined liver-kidney transplantation in methylmalonic acidemia.

A 13-year-old boy with non-B12-responsive methylmalonic acidemia (MMA) had chronic renal failure. Hemodialysis led to symptomatic and biochemical improvement. He subsequently received a combined liver-kidney transplant. After 16 months of follow-up he has a normal lifestyle and a marked reduction in plasma and urine methylmalonate.

Adolescent↗
PubMed1998

The contribution of depression and denial towards understanding the unawareness of symptoms in schizophrenic out-patients.

OBJECTIVES: Unawareness of schizophrenic symptoms was postulated to be partially attributable to patients denying symptoms in order to avoid depression. METHOD: The 24-item version of the Brief Psychiatric Rating Scale (BPRS) was administered to 41 schizophrenic patients (chart diagnoses were validated by a DSM-III-R checklist). The first 14 of these items were then used to gather information about patients' symptomatology from 55 relatives of patients. Unawareness of symptoms was calculated by subtracting patients' total for these 14 items from parents' totals. Two measures of depression were obtained. Subjective depression was the score on the depression item based on patients responses to interview questions, objective depression was the score based on interviews with relatives about their ill family member. Family functioning was also assessed by administering patients' relatives the Camberwell Family Interview and the FACES III. RESULTS: Hierarchical regression analyses revealed that both subjective and objective measures of depression were significantly related to unawareness; subjective depression was negatively related, and objective depression was positively related. The employed measures of family functioning were unrelated to unawareness of symptomatology. CONCLUSION: This opposing pattern of subjective and objective depression was interpreted as evidence of the self-deception which characterizes all defence mechanisms including denial.

Adult↗
PubMed1998

Does 'healing' benefit patients with chronic symptoms? A quasi-randomized trial in general practice.

This study was designed to examine the effects of a healer seeing chronically ill patients in a large semirural practice. The 57 patients were allocated alternately either to receive ten weekly healing sessions or to become waiting-list controls. Two weeks after completion of 'healing' 22 (81%) of the 27 study patients thought their symptoms had improved and 15 of these thought they had improved substantially. Study patients scored better than controls on both measures of symptoms (P < 0.05, P < 0.01), on anxiety and depression ratings (P < 0.01, P < 0.05) and on general function measured by the Nottingham Health Profile (P < 0.01). Treatment differences were still evident three months later for one of the measures of symptom change (P < 0.05) and for both anxiety and depression ratings (P < 0.01, P < 0.05). The percentages of natural killer cells (CD16, CD56) did not change greatly in either group. These results suggest that healing may be an effective adjunct for the treatment of chronically ill patients presenting in general practice. They do not distinguish between any specific effects of spiritual healing and non-specific effects such as relaxation; for further investigation, randomized controlled trials will be needed.

Adult↗
PubMed1998

Molecular, genetic and physiological analysis of Cladosporium resistance gene function in tomato.

Characterization of the DNA sequence of 4 tomato leaf mould disease resistance genes (Cf-2, Cf-4, Cf-5 and Cf-9) leads to the prediction that they encode C-terminally membrane anchored glycopeptides with many extracytoplasmic leucine rich repeats (LRRs). The N terminal LRRs are variable between the Cf-genes, suggesting a role in specificity, and the C terminal LRRs are more conserved, suggesting a role in signal transduction. Genetic analysis has revealed several Rcr genes that are required for Cf-gene function; their isolation will help us understand how Cf-genes work. Cf-9 confers responsiveness to pathogen-encoded Avr9 peptide on introduction to tobacco. Tobacco suspension cultures carrying the Cf-9 gene produce reactive oxygen species in response to Avr9 peptide, whereas untransformed cultures do not. The significance of these observations is discussed.

Cladosporium↗
PubMed1998

Increasing plant productivity in closed environments with inner canopy illumination.

Due to the high cost of habitable real estate associated with space travel and colonization, and the ultimate use of plants as the primary method of life support, it is necessary to develop cultivation methods whereby the highest sustainable level of productivity is achieved within the least amount of space. It is well known that in a dense plant canopy, lower leaves become shaded from above and eventually no longer contribute to carbon gain. In fact, they contribute to net respiratory carbon losses. One method of improving biomass production is to introduce light of suitable quantity and quality to the inner canopy, thereby utilizing unused photosynthetic capacity. By coupling microwave-powered lights to 100-mm-diameter glass tubes lined with 3M Optical Lighting Film, light with a spectral quality similar to that of sunlight was delivered to the inner canopy of a developing soybean crop. Results indicated that increases in productivity of 23-87%, as measured by CO2 assimilation, can be achieved in dense plant canopies (LAI approximately 6) when overhead lighting (40O-1200 micromoles m-2 s-1) is supplemented with inner canopy illumination.

Biomass↗
PubMed1998

Trauma deaths in a rural area.

This study was undertaken in order to clarify the causes of death amongst rural trauma victims in Union County, Arkansas. Over a five-year time interval, seventy-two percent (n = 60) of the trauma deaths occurred at the geographical site of injury before the arrival of any emergency medical services. Thus, prolonged time to discovery of trauma victims accounts for the most significant factor leading to trauma deaths in Union County. Education regarding injury prevention must continue to be emphasized to the public.

Adolescent↗