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Biomedical subjects

T M Thomas

Publications and source records attributed to T M Thomas.

At least 19 recordsLinked to original sources
PubMed2006

Characterization of the structure and properties of authentic and counterfeit polypropylene surgical meshes.

A counterfeit version of the Ethicon Prolene polypropylene mesh was distributed to hospitals and clinics and unintentionally implanted into patients undergoing tension-free hernia repair. On December 19, 2003, the Food and Drug Administration (FDA) issued a public health web notification indicating that the counterfeit mesh was not sterile or safe to use. To develop safety recommendations for patients with the counterfeit mesh implant, we compared the counterfeit's structural, physical, chemical and mechanical properties with polypropylene meshes previously cleared by FDA. The mesh fibers for all the products tested were found to have similar chemical and physical properties. The mechanical properties were directly related to the knitted structure (loop size, repeat distance, fabric tightness) and the porosity. Extracts from the counterfeit mesh passed cytotoxicity screening tests. The FDA further recommended that if the mesh had been inadvertently implanted, then those patients should be monitored as would be the practice for any patient with an implanted surgical mesh.

Herniorrhaphy↗
PubMed2003

Preparation of monoclonal antibodies using the electrophoresis separation instrument, Gradiflow.

Gradiflow, a preparative electrophoresis separation device, was utilized to develop and test generic protocols for the preparation of monoclonal antibodies (MAbs) from tissue culture supernatant and ascites fluid. The charge based protocol separated the high pI antibodies from the lower isoelectric points (pI) contaminants by either moving the antibody (ascites fluid) or contaminants (tissue culture supernatant) through a polyacrylamide separation membrane. A total of 60 separations were performed with tissue culture supernatant, and a further 30 separations with ascites fluid. The Gradiflow procedure resulted in higher yields, equivalent functionality and similar purity compared with affinity chromatography antibody preparation on protein A and G. The results suggest that the Gradiflow protocols may be an alternative method of antibody preparation for these samples.

Animals↗
PubMed2002

Preparative electrophoresis: a general method for the purification of polyclonal antibodies.

Antibodies were purified from normal rabbit, sheep, goat, rat, human and bovine serum using preparative electrophoresis on a Gradiflow in a single-step process using an asymmetrical cartridge with three different pore size polyacrylamide membranes. Recoveries in each case were over 80% and were higher than those obtained using affinity chromatography on protein A, protein G or protein L. Degree of purity was at least comparable with these methods. These results suggest that preparative electrophoresis can be considered a general method for the purification of research quantities of antibodies from multiple serum sources and may be particularly useful where the reactivity with protein A, G or L is unknown.

Animals↗
PubMed2000

Cortical inputs to m2-immunoreactive striatal interneurons in rat and monkey.

Previous anatomical studies have been unsuccessful in demonstrating significant cortical inputs to cholinergic and somatostatinergic striatal interneurons in rats. On the other hand, electrophysiological studies have shown that cortical stimulation induces monosynaptic EPSPs in cholinergic interneurons. It has been proposed that the negative anatomical findings might have been the result of incomplete labeling of distal dendrites. In the present study, we reinvestigated this issue using m2 muscarinic receptor antibodies as a selective marker for cholinergic and somatostatinergic interneurons in the striatum. This was combined with injections of either the anterograde tracer biotinylated dextran amine (BDA) in the monkey prefrontal cortex or aspiration lesion of the sensorimotor cortex in rats. The results showed that, in both species, a small percentage (1-2%) of cortical terminals make asymmetric synaptic contacts with m2-immunoreactive interneurons in the striatum. Interestingly, the majority of these synapses are onto small dendritic spines or spine-like appendages, as opposed to dendritic shafts and/or cell bodies. Thus, m2-containing striatal interneurons do receive direct cortical inputs and can, therefore, integrate and modulate cortical information flow through the striatum. Although the density of cortical terminals in contact with individual striatal interneurons is likely to be relatively low compared to the massive cortical input to projection neurons, both cholinergic and somatostatinergic interneurons display intrinsic properties that allow even small and distal inputs to influence their overall state of neuronal activity.

Animals↗
PubMed1999

Neonatal Marfan syndrome: a case report.

A case of neonatal Marfan syndrome is presented. The patient was noted to have cardiomegaly and tricuspid regurgitation on antenatal ultrasound scan. She was born with long, slender fingers and toes, an aged appearance and non-paralytic hypotonia. Echocardiogram revealed a dilated right atrium, right ventricle, dysplastic tricuspid valve and severe tricuspid regurgitation. She subsequently died of severe heart failure. Post-mortem examination showed the pathological features of lobar emphysema and cystic medial necrosis of the aorta. These features supported the diagnosis of neonatal Marfan syndrome. Nucleotide sequencing showed substitution of G by A at codon 1032 in exon 25 located in the long arm of chromosome 15. This resulted in the substitution of a cysteine by a tyrosine. A de novo mutation is suggested by the absence of affected family members.

Cardiomegaly↗
PubMed1998

The effects of temperature on the kinetics and stability of mesophilic and thermophilic 3-phosphoglycerate kinases.

The effects of temperature on the kinetic parameters kcat and Km, for three isolates of the highly conserved monomeric enzyme 3-phosphoglycerate kinase (PGK), were investigated in detail using a rapid automated kinetics apparatus. PGK was purified from the thermophilic bacterium Thermoanaerobacter sp. Rt8.G4 (optimum growth temperature 68 degrees C), the mesophile Zymomonas mobilis (optimum growth temperature 32 degrees C) and a second, unidentified, soil mesophile designated unid A (optimum growth temperature 27 degrees C). The kinetic behaviour with temperature of each PGK preparation was distinct, despite the conserved nature of the enzyme. The kcat values increased with temperature, but not as rapidly exponentially, as might be expected from the Arrhenius equation. Maximum kcat values were at much higher temperatures than the optimum growth temperatures for the mesophiles, but for the thermophile the temperature of maximum kcat was close to its optimum growth temperature. Km values were in general nearly constant through the lower temperature ranges, but increased substantially as the optimum temperature (highest kcat) was passed. Thermal irreversible denaturation of the PGK proteins was also investigated by measuring loss of activity over time. In a dilute buffer, Arrhenius plots for denaturation were linear, and the calculated apparent energy of activation (Eact) for denaturation for the thermophilic PGK was 600 kJ.mol-1, whereas for the mesophilic enzymes the values were 200-250 kJ.mol-1. In the presence of substrates, a considerable stabilization occurred, and in the case of the Z. mobilis enzyme, the apparent Eact was increased to 480 kJ.mol-1. A theoretical explanation for these observations is presented. Comparing the kinetics data with irreversible denaturation rates determined at relevant temperatures, it was clear that kcat values reached a maximum, and then decreased with higher temperature before irreversible denaturation had any significant influence.

Bacteria, Anaerobic↗
PubMed1997

Muscarinic acetylcholine receptor subtype, m2: diverse functional implications of differential synaptic localization.

The muscarinic acetylcholine receptor (mAChR) molecular subtype, m2, has been postulated to be the presynaptic cholinergic autoreceptor in many brain regions. However, due to a lack of subtype-specific pharmacological agents, conclusive evidence for m2 as an autoreceptor remains elusive. The development of subtype-specific antibodies has enabled extensive characterization of the synaptic localization of the m2 subtype. Specifically, double-labeling immunocytochemistry with m2 antibodies and antibodies to the vesicular acetylcholine transporter (VAChT), a novel specific marker of cholinergic terminals, in the striatum has allowed the first direct anatomical evidence of m2 localization in cholinergic terminals. Additionally, other anatomical studies in striatum and the septohippocampal pathway have revealed that this subtype is also expressed presynaptically in non-cholinergic terminals, and is postsynaptically expressed in both cholinergic and non-cholinergic neurons. The implications of these data for understanding the functional roles of this subtype are discussed.

Animals↗
PubMed1997

Mammary myofibroblastoma with leiomyomatous differentiation.

An unusual example of mammary myofibroblastoma in a 36-year-old woman was reported. The central portion resembled mammary myofibroblastoma or solitary fibrous tumor of other sites and showed reactivity for CD34 and muscle-specific actin, with few cells staining for desmin. The peripheral portion resembled leiomyoma and showed strong reactivity for actin and desmin but only focal staining for CD34. We interpret this tumor as mammary myofibroblastoma showing frank peripheral leiomyomatous differentiation. Although closely related to solitary fibrous tumor, mammary myofibroblastoma appears slightly different because of its consistent slant toward myoid differentiation in the form of actin and variable desmin reactivity as opposed to the rare and sparse immunohistochemical expression of myoid features by solitary fibrous tumors of other sites. This case demonstrates this phenomenon carried to an extreme, a feature not previously documented in mammary myofibroblastoma. It is of interest to note the modulation of the antigenic profile with the differentiation process, that is, loss of CD34 and gain of desmin accompanying the myoid differentiation.

Adult↗
PubMed1992

Helicobacter pylori-related gastritis and gastric ulcer. A continuum of progressive epithelial degeneration.

One hundred forty-five consecutive gastric biopsy specimens showing colonization by Helicobacter pylori (HP) were studied. Biopsy specimens were obtained from patients with the following conditions: gastric ulcer (GU; 76), active chronic gastritis (ACG; 52), GU with duodenal ulcer (DU; 10), and ACG with DU (7). The mean age of the patients in the ACG group was 8.6 years less than the patients in the GU group. Helicobacter pylori colonization and HP-induced epithelial degeneration (ED) were quantified by a grading system (grades 0 to 6) comprising both focal and global scores for bacterial density (HP grade) and severity of ED (ED grade). The ED grade was directly proportional to the HP grade in all biopsy specimens. Gastric ulcer biopsy specimens were associated with higher HP grades: HP grade more than 5 in 25 cases (32.9%) and ED grade more than 5 in 18 cases (23.6%) of GU compared with similar respective scores in 9 cases (17.9%) and 2 cases (3.8%) of ACG. The difference was due primarily to a higher global score of bacterial density and higher focal score of ED in the GU biopsy specimens. These results support the hypothesis that HP-positive ACG and HP-positive GU are lesions within a single disease spectrum. Heavy HP colonization and severe HP-induced epithelial damage are predisposing factors in ulcerogenesis. Because HP-positive ACG is probably a preulcerative state, eradication of the bacteria in HP-positive ACG might prevent subsequent GU.

Biopsy↗
PubMed1992

Modes of Helicobacter colonization and gastric epithelial damage.

A total of 144 gastric biopsies colonized by Helicobacter-like organisms were studied under light and differential interference contrast microscopy for the modes of bacterial colonization. Biopsies were also graded for the degree of epithelial damage (epithelial-damage-grade: 0 to 6, in ascending order of severity) and density of Helicobacter-like organism (Helicobacter-grade: 0 to 6, in ascending order of bacterial density). Three modes of colonization were identified: free-in-mucus, surface-adhesion and intercellular colonization. Because light microscopy cannot definitely prove the presence of intracellular colonization, bacteria located between cells and below the apical cell border were counted together as intercellular colonization. Bacteria free-in-mucus were seen in all biopsies. Surface adhesion was seen in 50-87.9% of biopsies, without obvious correlation with the epithelial-damage- and Helicobacter-grades. The incidences of intercellular and intracellular colonization were directly proportional to the epithelial-damage- and Helicobacter-grades. Free-in-mucus as the predominant mode of colonization was mainly seen in biopsies with lower (1-3) epithelial-damage- and Helicobacter-grades. Conversely, biopsies with intercellular colonization as the predominant mode of colonization were mainly cases with higher (4-6) epithelial-damage- and Helicobacter-grades. In cases showing predominantly bacteria between cells, 69.2% had a gastric ulcer whereas only 38.8% of cases showing predominantly bacteria free-in-mucus showed ulceration (P < 0.01). These results indicate that Helicobacter-like organisms can invade and penetrate between epithelial cells. When free-in-mucus, Helicobacter-like organisms are less likely to induce epithelial damage. However, the more invasive modes of colonization (intercellular) were associated with severe epithelial damage and high Helicobacter density.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1984

Localization and characterization of gastrin/cholecystokinin-like immunoreactivity in the central nervous system of Aplysia californica.

Gastrin/cholecystokinin-like immunoreactivity (G/CCK-LI) was localized by immunocytochemistry in neurons in the central nervous system of Aplysia californica. Neuronal cell bodies were specifically immunostained in the buccal, cerebral, pedal, and abdominal ganglia but not in the pleural ganglia. Neural G/CCK-LI processes were observed in the neuropil of all ganglia and connectives and in some but not all of the peripheral nerves examined. Somata containing G/CCK-LI ranged from 15 to 200 micron in diameter. Ganglionic G/CCK-LI was most efficiently extracted in neutral or basic solutions and consisted mainly of a substance eluting in a volume corresponding to a peptide of between 8 and 17 amino acid residues on gel filtration. This G/CCK-LI diluted in parallel to mammalian gastrin in radioimmunoassays using two antisera differing in their specificities for the bioactive COOH-terminal region of mammalian G/CCK. We conclude that G/CCK-LI is distributed widely in the central and peripheral nervous systems of Aplysia californica and that this immunoreactivity probably represents a small peptide which is similar but not identical to mammalian gastrins and cholecystokinins at the functionally critical COOH terminus.

Amino Acid Sequence↗
PubMed1981

Management of urinary incontinence in patients with multiple sclerosis.

We investigated the management of urinary incontinence in 50 patients with multiple sclerosis (MS) in two London boroughs. Only seven appeared to be satisfied with the management of their bladder problems. A total of 51 suggestions was made for improving management in 33 of the patients. Most of these suggestions involved services which were available though not being used. The management of urinary incontinence in patients with MS should be tailored to the requirements of the individual. Alternative forms of management may often not be reaching patients who might benefit from them.

Adolescent↗