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Biomedical subjects

J N Thomas

Publications and source records attributed to J N Thomas.

At least 19 recordsLinked to original sources
PubMed2006

How we do it: diagrammatic recording of tympanomastoid procedures.

Accurate documentation of the operative findings of tympanomastoid procedures is essential for effective patient management and to satisfy the growing demands of clinical audit. Due to the three-dimensional complexity of the middle ear, it is difficult to represent graphically. Consequently, most surgeons only describe subjectively their operative, otological findings. We present for the first time a simple middle ear template which provides an objective tool to improve the recording of tympanomastoid procedures.

Documentation↗
PubMed2000

Cardiac sarcoplasmic reticulum and sarcolemmal proteins separated by two-dimensional electrophoresis: surfactant effects on membrane solubilization.

We evaluated the use of the alkyaryl amidosulfobetaine zwitterionic detergent, designated as C8psi, to facilitate the solubilization of cardiac subcellular, membrane-associated proteins. Hearts from 7-week-old male Sprague-Dawley rats were isolated, and the left ventricles dissected and subsequently homogenized. The sarcolemma (SL) and the sarcoplasmic reticulum (SR) were isolated from different homogenate preparations originating from rat hearts by ultracentrifugation methods. The isolated membrane preparations were solubilized and the proteins precipitated. After resuspension, protein separation was achieved in first-dimensional IEF using an immobilized (pH 4-7) gradient and in the second dimension using 12% sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE). Gels were then stained, images analyzed, and protein spots excised for subsequent identification. Protein identification from both SR and SL samples did not identify any of the known major membrane-associated proteins. Solubilization of whole tissue lysates with C8psi resulted in no increase in the total number of proteins detected relative to samples solubilized in the presence of 3-[(3-cholamidopropyl)dimethylammonio]-1-propanesulforate (CHAPS). The data suggest the utility of newer surfactants such as C8psi to improve both the resolution of (2-D) protein profiles and increase the number of proteins extracted from subcellular organelle fractions.

Animals↗
PubMed1997

Supplemental melatonin increases clonal lifespan in the protozoan Paramecium tetraurelia.

The hypothesis that melatonin supplementation can increase the lifespan of a single-celled organism was tested by the administration of melatonin to the ciliated protozoan Paramecium tetraurelia. Melatonin supplementation in dim red light at a dose of 0.043 mM (10 mg/L) of nutrient media (bacterized Cerophyl) per day, followed by incubation for 23 hr in darkness, increased the mean clonal lifespan of Paramecium tetraurelia in days by percentages ranging from 20.8% (P < 0.01, two-tailed t-test) to 24.2% (P < 0.01, ANOVA) over controls. Maximum clonal lifespan in days was also increased in melatonin-supplemented cells, from 14.8% to 24.0% over controls. Mean clonal lifespan in fissions was not significantly greater in melatonin-supplemented cells, with values ranging from 6.0% to 15.5% over controls. Maximum clonal lifespan in fissions did not differ appreciably, with values ranging from 1.0% to 9.1% over controls, except in the case of cells selected for rapid division rates, in which melatonin-supplemented cells (393 fissions) lived 20.9% longer than controls (325 fissions) in terms of cumulative cell doublings during the clonal lifespan. The finding that melatonin supplementation increased clonal lifespan in Paramecium tetraurelia, an aerobic, single-celled organism, suggests that the mechanism of melatonin's longevity-promoting effects may be intracellular.

Animals↗
PubMed1993

Preliminary survivorship report on combined intraoperative radiation and hyperthermia treatments for unresectable pancreatic adenocarcinoma.

Five patients with unresectable pancreatic adenocarcinoma were treated with simultaneous intraoperative radiotherapy and intraoperative hyperthermia. Postoperative survivorship averaged 15.8 months, which compares favorably to a previous study in which 19 patients receiving intraoperative radiotherapy without intraoperative hyperthermia survived an average of 6.05 months. Three of the five patients following the experimental protocol of intraoperative radiotherapy and intraoperative hyperthermia with additional external beam radiotherapy are still alive, which may result in average postoperative survivorship exceeding 15.8 months.

Adenocarcinoma↗
PubMed1990

Assignment of intrachain disulfide bonds and characterization of potential glycosylation sites of the type 1 recombinant human immunodeficiency virus envelope glycoprotein (gp120) expressed in Chinese hamster ovary cells.

This report describes the structural characterization of the recombinant envelope glycoprotein (rgp120) of human immunodeficiency virus type 1 produced by expression in Chinese hamster ovary cells. Enzymatic cleavage of rgp120 and reversed-phase high performance liquid chromatography were used to confirm the primary structure of the protein, to assign intrachain disulfide bonds, and to characterize potential sites for N-glycosylation. All of the tryptic peptides identified were consistent with the primary structure predicted from the cDNA sequence. Tryptic mapping studies combined with treatment of isolated peptides with Staphylococcus aureus V8 protease or with peptide:N-glycosidase F followed by endoproteinase Asp-N permitted the assignment of all nine intrachain disulfide bonds of rgp120. The 24 potential sites for N-glycosylation were characterized by determining the susceptibilities of the attached carbohydrate structures to peptide:N-glycosidase F and to endo-beta-N-acetylglucosaminidase H. Tryptic mapping of enzymatically deglycosylated rgp120 was used in conjunction with Edman degradation and fast atom bombardment-mass spectrometry of individually treated peptides to determine which of these sites are glycosylated and what types of structures are present. The results indicate that all 24 sites of gp120 are utilized, including 13 that contain complex-type oligosaccharides as the predominant structures, and 11 that contain primarily high mannose-type and/or hybrid-type oligosaccharide structures.

Amino Acid Sequence↗
PubMed1990

Endoscopic examination of the neonatal larynx at extubation: a prospective study of variables associated with laryngeal damage.

Despite postmortem and clinical studies, the etiological factors that determine why only a proportion of intubated neonates develop subglottic stenosis remain unclear. This prospective study was initiated to identify factors that were associated with laryngeal abnormalities secondary to intubation. Thirty neonates were examined at extubation by two independent observers blinded to the neonate's ventilatory history. Thirty-six possible prognostic indicators were recorded for each neonate. After screening by univariate (chi 2) analysis, 10 indicators were selected for further analysis. Of these 10 selected only two indicators showed an association with the laryngeal appearance. Active neonates had significantly more abnormalities in the supraglottis (P = 0.004) than those who were quiescent. Younger neonates had more abnormalities in the glottis though the significance level was marginal (P = 0.056). Other prognostic indicators, including birthweight, gestational age, duration of intubation and frequency of intubation, were not significantly related to laryngeal appearance. This study supports the hypothesis that the etiology of laryngotracheal stenosis is multifactorial, and has identified two possible etiological factors: age and neonatal activity. Neonatal activity has not been identified previously as an etiological factor. The contribution of individual factors may vary from one neonatal unit to another, as a result of variation in intubation, ventilation and extubation policy. This could explain the inconsistency in etiological factors identified by previous studies. It is therefore not yet possible to recommend a standard technique for the ventilation of premature neonates that would further reduce the incidence of laryngotracheal stenosis.

Erythema↗
PubMed1986

Optimization of environment for high density Vero cell culture: effect of dissolved oxygen and nutrient supply on cell growth and changes in metabolites.

This study was initiated for optimization of the environment of a technologically useful mammalian cell line for high density production. Cultures of Vero cells on microcarriers were perfused with 100%, 50%, 25% and 12.5% modified L15 media (galactose was replaced with 10 mM-fructose, with 4 mM-glutamine and 5% foetal bovine serum) in phosphate-buffered saline at either 4 or 8 vol. day-1. Cell growth, pH, dissolved oxygen, and changes in the metabolites, lactate to pyruvate and lactate to ammonia indices, demonstrated that under the conditions used in the present study, perfusion of cultures with 50% L15 medium in PBS at 8 vol. day-1 provided the optimum microenvironment for Vero cell growth. The highest cell density in the perfused cultures was 3 X 10(7) cells ml-1, which at these conditions was ten times higher than the maximum cell density (3 X 10(6) cells ml-1) obtained in a batch culture. Nutrient supply and conditioning factors were the most probable growth-limiting factors in cultures that were perfused with 12.5% and 25% L15 media, while multilayering, limitation of available oxygen, and accumulation of metabolic end products in the cellular microenvironment were the most probable causes of a density-dependent inhibition of cell growth observed under the optimized and overfed (supply of 100% L15 medium at the rate of 8 vol. day-1) culture conditions. Under the optimized environmental condition, the major source of energy was probably glutamine during the first week. However, significant utilization of fructose became evident at higher cell densities during the second week, when lactate production dramatically declined and reached an almost undetectable level, while respiration progressively assumed the predominant role in energy production. It is postulated that 'available' oxygen in the multicell-layered microenvironment of the optimized cultures was higher than in the overfed culture due to the greater utilization rate of oxygen for oxidation of excess nutrients in the overfed culture.

Ammonia↗
PubMed1984

Alteration of regression of cholesterol accumulation in rats by dietary pectin.

Male, Wistar rats (50-74 g) were given a semi-purified diet containing cholesterol (10 g/kg diet) for 4 weeks, groups of control and experimental animals killed, and the remainder of the cholesterol-fed animals given either a semi-purified cholesterol-free diet without a fibre source or a similar diet with pectin (50 g/kg diet) for 8 weeks. Animals were killed at 2-week intervals and serum and liver cholesterol and triglycerides, faecal neutral steroids and acidic steroids measured. Animals given pectin had significantly lower serum cholesterol levels than animals given the basal diet after 4 and 6 weeks. Both experimental groups efficiently decreased their liver cholesterol levels during regression. Bile acid excretion was elevated in both groups, especially in rats receiving pectin, but neutral steroid excretion was unchanged. The increase in bile acid excretion was primarily in the form of chenodeoxycholic acid and its metabolites. This increased bile acid excretion is postulated to result from stimulation of the normal mechanism for increased steroid excretion in the rat, i.e. a change in the value of cholic: chenodeoxycholic acid or from a mechanism not yet elucidated.

Animals↗
PubMed1979

An ultrastructural study of a nasal haemangioendothelioma.

A malignant haemangioendothelioma of the nose has been examined with the electron microscope. The tumour is predominantly poorly differentiated with only little evidence of its vascular ancestry identified. The cells are polygonal with a wide spectrum of organelles, including microfilaments. A conspicuous feature was the presence of cytoplasmic fenestrae developing into intracytoplasmic vacuolated spaces. The satisfactory progress of this patient is noted, and the value of electron microscopy in enabling an early and accurate diagnosis of this tumour to be made is emphasised.

Adult↗
PubMed1978

Partial upper airway obstruction and sleep apnoea.

An unusual case is described in which partial upper airway obstruction led to a sequence of events characterized by sleep disturbance, enuresis, somnolence and cardio-respiratory collapse. The upper airway obstruction was not immediately apparent as the cause of subsequent clinical events. Attention is drawn to the general medical problems which may be produced by upper airway obstruction, with particular reference to those accompanying obesity and abnormal stature.

Achondroplasia↗