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Biomedical subjects

M Fenton

Publications and source records attributed to M Fenton.

At least 55 records · Page 3Linked to original sources
PubMed1995

DNA ploidy status in 84 ocular melanomas: a study of DNA quantitation in ocular melanomas by flow cytometry and automatic and interactive static image analysis.

Deoxyribonucleic acid (DNA) ploidy was quantified in 84 ocular melanomas (median follow-up, 11-years) by flow cytometry, CAS 200 interactive image analysis, and Pathology Image Processing Environment (PIPE; Department of Quantitative Pathology, Free University, Amsterdam, The Netherlands) automatic image analysis (75). Overall, 32.1% of the melanomas were aneuploid, 2.3% were tetraploid, and 66.6% were diploid. Pathology Image Processing Environment analysis estimated DNA ploidy in 12 tumors that were unprocessable by flow cytometry. Of 10 tumors that were diploid by flow cytometry, PIPE detected stemline aneuploidy in five and some aneuploid cells in five more. Seven tumors were aneuploid by PIPE but diploid by CAS 200, five of which contained occasional DNA aneuploid cells on the CAS 200 histograms. Pathology Image Processing Environment analysis quantified tumor samples with an average of 500 (250 to 1,050) cells in less than 10 minutes. All cells classified as spindle A according to the Callender system (more than 10,000) were diploid. Spindle B and epithelioid cells occupied both diploid and aneuploid peaks on the DNA histograms. Dioxyribonucleic acid variables did not correlate with established prognosticators, such as Callender cell type, largest tumor dimension, or glaucoma, nor did they reach significance by univariate and multivariate analyses. The value of these findings as a diagnostic support in uveal melanoma, particularly in combination with fine needle aspiration biopsy, is discussed.

DNA, Neoplasm↗
PubMed1995

Energetic consequences of flight speeds of foraging red and hoary bats (Lasiurus borealis and Lasiurus cinereus; Chiroptera: Vespertilionidae)

We used Doppler radar readings of the flight speeds of foraging, lactating female Lasiurus borealis (N=826) and Lasiurus cinereus (N=544) to test morphologically based predictions about their flight performance. Both species flew at speeds (V=6.7 and 7.7 m s-1, respectively) that differed significantly from predicted minimum power speed (Vmp; 4.0 and 5.08 m s-1, respectively) or predicted maximum range speed (Vmr; 5.25 and 6.69 m s-1, respectively), perhaps reflecting the active pursuit of moths performing evasive manoeuvres. Estimates of costs of flight and lactation are combined with data on prey size together with encounter and capture rates to illustrate the energetic benefits accruing to these species when they forage in concentrations of insects.

Journal Article↗
PubMed1994

Cytokine dysregulation and the initiation of systemic autoimmunity.

Autoimmunity (AI) exemplifies the potent and destructive activity expressed by the immune system when normal constraints against self-reactivity are lost or compromised. We have previously described a dramatic and intrinsic defect in cytokine expression in macrophages (M phi) from young AI-prone mice [1-3]. There are two points in particular that we believe speak to the importance of this observation: (i) Cytokine dysregulation is distinguished from many of the aberrancies reported in AI-prone mouse strains in that, as an inherent trait, it cannot arise as a consequence of the disease process. (ii) This defect is a remarkably consistent characteristic of M phi from strains that develop manifestations of systemic AI, including MRL/+, NZB, NZB/W F1, BXSB, and NOD, and distinguishes these strains from mice whose disease is predicated on defects in apoptosis (e.g., the lpr and gld mutations). The multigenic basis for disease and renal pathology in the former strains more closely mirror human lupus than do the disease manifestations of lpr and gld mice. In light of clear evidence that cytokines are key mediators of lymphocyte growth and function, a defect in the cytokine network has the potential to disrupt the normal regulation of self-reactivity, leading to the initiation of systemic AI.

Animals↗
PubMed1994

Expression of the symbiotic plasmid from Rhizobium leguminosarum biovar trifolii in Sphingobacterium multivorum.

An inoculant strain of Rhizobium leguminosarum biovar trifolii containing a Tn5 marked symbiotic plasmid transferred this plasmid by conjugation to Sphingobacterium multivorum, an organism that can be found in soil. The transconjugant bacteria nodulated the roots of white clover (Trifolium repens) seedlings but did not fix atmospheric nitrogen. Microscopic examination revealed abnormal nodule structures. Bacteria isolated from the nodules were shown to be closely related to the recipient S. multivorum and Southern blots of genomic digests probed with nodA DNA confirmed that the transconjugants contained symbiotic genes. This is the first report of the spontaneous transfer, by conjugation, of a symbiotic plasmid from R. leguminosarum biovar trifolii to S. multivorum.

Acyltransferases↗
PubMed1993

Deoxyribonucleic acid ploidy studies in choroidal melanomas.

In several tumors of different organ sites, the amount of DNA in a cell (ploidy) is associated with malignancy. We performed DNA quantitation in 21 choroidal melanomas and compared flow cytometry with image analysis in 11 of these melanomas. We modified our preparation technique to overcome problems with pigment and control cell populations in the image analysis group. Fifteen tumors were diploid and two tumors were tetraploid. Four tumors were unprocessable by flow cytometry, but two of these tumors were diploid by image analysis. Image analysis also detected tetraploidy in two tumors that were diploid by flow cytometry. During image analysis, cells were classified according to the Callendar classification and histograms were plotted for each cell type. All spindle A cells were diploid and most tetraploid peaks were formed by epithelioid cells. The use of image analysis on small samples of choroidal melanomas may be of value both in confirmation of diagnosis and prognosis of these lesions, and perhaps therapeutically, for example, in the monitoring of radiation treatment.

Choroid Neoplasms↗
PubMed1993

Prognostic factors following enucleation of 111 uveal melanomas.

Follow up information was retrieved on 111 patients who underwent enucleation for uveal melanoma between 1964 and 1987, allowing a minimum postoperative period of 5 years. Univariate survival analysis was carried out using Kaplan-Meier curves and the differences between the curves were analysed with the Mantel-Cox test. Multivariate analysis used the Cox proportional hazards model. Univariate analysis isolated each of the following as significant prognosticators: largest tumour diameter (LTD) (p < 0.002), presence of epithelioid cells (p < 0.03), and glaucoma (p < 0.001). A combination of cell type, glaucoma, and LTD (p < 0.0001) had strong and independent prognostic significance in multivariate analysis. The results of this series are compared with previous studies and the value of cell type information and new quantitative parameters is discussed.

Adolescent↗
PubMed1992

Chromatographic separation of cholesterol in foods.

Based on the current literature and on experience gained in the laboratory, a simplified procedure using direct saponification (0.4 M potassium hydroxide in ethanol and heating at 60 degrees C for 1 h) is the most appropriate method for the determination of total cholesterol in foods. Extraction of the unsaponifiable matter with hexane is efficient and no extra clean-up is required before quantification. An internal standard, 5 alpha-cholestane or epicoprostanol, should be added to the sample prior to saponification and, together with reference standards, carried through the entire procedure to ensure accurate results. A significant improvement in cholesterol methodology has been achieved by decreasing the sample size and performing all the sample preparation steps in a single tube. The method has the advantages of elimination of an initial solvent extraction for total lipids and errors resulting from multiple extractions, transfers, filtration and wash steps after saponification. The resulting hexane extract, which contains a variety of sterols and fat soluble vitamins, requires an efficient capillary column for complete resolution of cholesterol from the other compounds present. The development of fused-silica capillary columns using cross-linked and bonded liquid phases has provided high thermal stability, inertness and separation efficiency and, together with automated cold on-column gas chromatographic injection systems, has resulted in reproducible cholesterol determinations in either underivatized or derivatized form. If free cholesterol and its esters need to be determined separately, they are initially extracted with other lipids with chloroform-methanol followed by their separation by column or thin-layer chromatography and subsequently analysed by gas or liquid chromatography. Although capillary gas chromatography offers superior efficiency in separation, the inherent benefits of liquid chromatography makes it a potential alternative. Isotope dilution mass spectrometry has been widely accepted as a reliable analytical method for highly accurate determination of cholesterol in serum and several definitive methods have been reported. The combination of capillary gas chromatography with mass spectrometry has become an excellent approach for the determination of cholesterol in complex mixtures of sterols and tocopherols, providing high resolution with positive identification. When used to determine cholesterol in multi-component foods, spectrophotometric methods have been documented to overestimate significantly the amount of cholesterol owing to the presence of other interfering substances. A re-evaluation of food products should be undertaken using the more specific chromatographic methods to accumulate data that will more accurately reflect the true cholesterol content.

Cholesterol↗
PubMed1992

The future of podiatric medical education. Cautious optimism.

The leadership of the Pennsylvania College of Podiatric Medicine sets forth the following treatise on the outlook for podiatric medical education into the 21st century. Despite the seemingly impossible challenges facing the profession and its students, it is their opinion that the future is bright and with dedicated effort the profession will become stronger in the years ahead.

Education, Medical↗
PubMed1989

Effect of exogenous pyruvate on acrylamide neuropathy in rats.

The protective effect of exogenous sodium pyruvate on the distal-proximal progression of experimental acrylamide neuropathy in rats was examined. Incorporation of 2% (w/w) sodium pyruvate powder in the diet of rats receiving subcutaneous injections of an aqueous solution of acrylamide (35 mg/kg/day, 5 days/week) retarded the onset and development of functional, morphological, and biochemical measures of acrylamide neuropathy. Pyruvate supplementation did not alter hexobarbital sleep time or zoxazolamine paralysis time, two in vivo measures of microsomal mixed-function oxidase activity, and the disposition of radioactivity in plasma or sciatic nerve following subcutaneous injection of [14C]acrylamide. Although acrylamide can interfere with energy metabolism at a variety of sites where pyruvate can rescue neurons (axons), the data of this study are consistent with our earlier hypothesis that acrylamide neuropathy may be associated with a glycolytic deficit. The exact site of pyruvate protection is unknown. Exogenous pyruvate is perhaps utilized by axons to circumvent toxin-induced glycolytic inhibition and provide chemical energy for fast axonal transport.

Acrylamide↗
PubMed1988

Moral distress in clinical practice: implications for the nurse administrator.

The purpose of this paper is to describe the experience and effect of moral distress in clinical practice and to present the implications of this phenomena for nurse administrators. Findings from three recent investigations provide the descriptive data for this paper. Nurses in clinical practice are frequently confronted with situations which challenge personal moral beliefs. Life and death events, sudden unexpected emergencies and professional role conflict have been identified as some examples of the kinds of situations that are most difficult to cope with. Feelings of emotional distress may occur as a result of participation in a patient care situation which involves an ethical issue. Personal and professional wholeness may be significantly compromised by the ineffective resolution of such issues. Moral distress may affect the nurse's ability to care for the patient and may require a significant period of resolution. Moral distress has been identified as one reason that nurses choose to leave their jobs and occasionally to leave the profession. Implications for the nurse administrator include a responsibility to be aware and supportive of the nurse in this situation. Commitment to developing effective strategies to assist nurses to cope successfully with the ethical dimension of clinical practice is an important management concern.

Adaptation, Psychological↗
PubMed1987

Two year electrophysiology follow-up in quinine amblyopia. A case report.

A 19-year-old girl presenting with quinine amblyopia had serial electrophysiology studies over a 2 year period. Visually evoked responses and the electro-oculogram were abolished early. By 2 months the VER and visual acuity had returned to normal. The electroretinogram, initially mildly subnormal, became virtually abolished by 2 months. No recovery in cone function took place. Of the rods 50% regained function with normal latency by 1 year, but receptor sensitivity did not return to normal until 2 years after ingestion. The electro-oculogram also recovered slowly over a 2 year period. This pattern suggest that quinine exerts a direct toxic effect on the cells of the outer retina and pigment epithelium, as well as on the ganglion cells.

Adult↗
PubMed1979

Immunosupression of the primary and secondary immune response by an IgM plasmacytoma (TEPC-183).

Previously we had established that TEPC-183 IgM(K) suppressed the primary immune response (IR) to both the T-dependent antigens 2,4-dinitrophenyl-haemocyanin (DNP-HCY) and T-independent pneumococcal polysaccharides. In the current investigation, the effect of TEPC-183 on an ongoing immune response to SS-III and DNP-HCY was examined. It was found that when TEPC-183 was injected 6 days after the initial antigen injection, at the height of the primary IR, the response was significantly suppressed to SS-III and to the DNP ligand. In addition, suppression of the secondary IR occurred when mice were injected with tumour as late as 35 days after the first antigen injection. Tumour removal lifted the immunosuppression to DNP and the tumour-removed group had a similar number of both direct and indirect anti-DNP-PFC, although HA levels were still reduced. When mice were pretreated with serum from normal mice or serum or ascites from TEPC-183 bearing mice, one day prior to and on the day of antigen injection, the immune response to DNP was reduced by TEPC-183 serum but not by normal mouse serum (NMS), while the anti-SSS-III response was reduced by both NMS and TEPC-183 serum. Thus, NMS selectively suppressed the T-independent response, but only TEPC-183 serum suppressed both types of responses. The suppressive effect of serum on the IR of normal mice indicates a role for soluble regulatory suppressive factors present in the serum of normal and tumour-bearing mice. The data are consistent with the idea that the tumour exerts its effect on the inductive as well as the proliferative phase of the immune response.

Animals↗