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Biomedical subjects

T M Scott

Publications and source records attributed to T M Scott.

At least 19 recordsLinked to original sources
PubMed2006

Geographical variation in antibiotic resistance profiles of Escherichia coli isolated from swine, poultry, beef and dairy cattle farm water retention ponds in Florida.

AIMS: The aim of this study was to assess geographical variation in multiple antibiotic resistance (MAR) profiles of livestock Escherichia coli as well as to evaluate the ability of MAR profiles to differentiate sources of faecal pollution. METHODS AND RESULTS: More than 2000 E. coli isolates were collected from water retention ponds and manure of swine, poultry, beef and dairy farms in south, central and north Florida, and analysed for MAR using nine antibiotics. There were significant differences in antibiotic resistance of E. coli by season and livestock type for more than one antibiotic, but regional differences were significant only for ampicillin. Over the three regions, discriminant analysis using MAR profiles correctly classified 27% of swine, 49% of poultry, 56% of beef and 51% of dairy isolates. CONCLUSIONS: Regional variations in MAR combined with moderate discrimination success suggest that MAR profiles of E. coli may only be marginally successful in identifying sources of faecal pollution. SIGNIFICANCE AND IMPACT OF THE STUDY: This study demonstrates the existence of regional and seasonal differences in MAR profiles as well as the limited ability of MAR profiles to discriminate among livestock sources.

Agriculture↗
PubMed2004

Assessment of virulence-factor activity relationships (VFARs) for waterborne diseases.

Virulence-factor activity relationship (VFAR) is a concept that was developed as a way to relate the architectural and biochemical components of a microorganism to its potential to cause human disease. Development of these relationships requires specialised bioinformatics databases that do not exist at present. A pilot-scale VFAR database was designed for three different waterborne organisms: Escherichia coli, Norovirus and Cryptosporidium, to evaluate VFAR relationships. For the web-based database, each organism has separate pages containing virulence genes, occurrence genes, primer sets and probes, taxonomy, outbreaks, and serotype/species/genogroup/genotype. As the database continues to grow, it will be possible to relate the occurrence and prevalence of certain genes in various microorganisms to outbreak data and, subsequently, to establish the utility of using a combination of specific genes as markers of virulence and in establishing virulence-factor activity relationships (VFARs). The database and the VFARs established will be of use to the regulatory community as a way to assist with prioritising those organisms, which need to be regulated.

Animals↗
PubMed2003

Assessment of methods for detection of infectious Cryptosporidium oocysts and Giardia cysts in reclaimed effluents.

This study evaluates the occurrence of Cryptosporidium oocysts and Giardia cysts in reclaimed effluents if method 1623 with the Envirochek capsule filters (standard and high-volume [HV] filters) and a modified version of the Information Collection Rule method (ICR) with the polypropylene yarn-wound cartridge filter are used. The recovery efficiency of the analytical methods was evaluated with samples of reagent, tap, and reclaimed water by using flow cytometer-sorted spike suspensions. (Oo)cyst recovery efficiency determined filter performance and method reproducibility in the water matrix tested. Method 1623 with the Envirochek HV capsule filter generated significantly higher recovery rates than did the standard Envirochek filter and the modified ICR method. Notwithstanding, large variations in recovery rates (>80%) occurred with samples of reclaimed water, and none of the water quality parameters analyzed in the reclaimed effluents could explain such variability. The highest concentrations of indigenous oocysts were detected by method 1623 with the HV filter, which provided a sufficient number of oocysts for further confirmation of infectious potential. Confirmation of species and potential infectivity for all positive protozoan samples was made by using a nested PCR restriction fragment polymorphism assay and the focus detection method most-probable-number assay, respectively. The methodology and results described in the present investigation provide useful information for the establishment of pathogen numeric standards for reclaimed effluents used for unrestricted irrigation.

Animals↗
PubMed2001

Elution, detection, and quantification of polio I, bacteriophages, Salmonella montevideo, and Escherichia coli O157:H7 from seeded strawberries and tomatoes.

This study compared the effect of different physical and chemical treatments of strawberries and tomatoes to determine their ability to recover seeded viral and bacterial pathogens from produce surfaces. Solutions of salts, amino acids, complex media, and detergents were compared as eluants. Phosphate-buffered saline (PBS) containing 0.1% Tween 80 eluted the highest number of seeded microorganisms. Elution with this defined solution was then compared under different conditions of physical agitation. Rotary shaking for 20 min at 36 degrees C eluted higher numbers of viruses and bacteria than did low- or high-speed stomaching. Commercially available and laboratory prepared bacteriological differential media were compared for their ability to recover and distinguish eluted Salmonella Montevideo and Escherichia coli O157:H7 strains from seeded produce. The recovery of seeded bacterial pathogens was low when differential media containing selective ingredients were used (MacConkey sorbitol agar, XLD agar, MacConkey agar). Highest recoveries were obtained on a medium consisting of tryptic soy agar supplemented with sodium thiosulfate and ferric ammonium citrate compared with selective media that inhibited up to 50% of the growth of the eluted microorganisms.

Bacteriological Techniques↗
PubMed2000

Influence of salts on virus adsorption to microporous filters.

We investigated the direct and indirect effects of mono-, di-, and trivalent salts (NaCl, MgCl(2), and AlCl(3)) on the adsorption of several viruses (MS2, PRD-1, phiX174, and poliovirus 1) to microporous filters at different pH values. The filters studied included Millipore HA (nitrocellulose), Filterite (fiberglass), Whatman (cellulose), and 1MDS (charged-modified fiber) filters. Each of these filters except the Whatman cellulose filters has been used in virus removal and recovery procedures. The direct effects of added salts were considered to be the effects associated with the presence of the soluble salts. The indirect effects of the added salts were considered to be (i) changes in the pH values of solutions and (ii) the formation of insoluble precipitates that could adsorb viruses and be removed by filtration. When direct effects alone were considered, the salts used in this study promoted virus adsorption, interfered with virus adsorption, or had little or no effect on virus adsorption, depending on the filter, the virus, and the salt. Although we were able to confirm previous reports that the addition of aluminum chloride to water enhances virus adsorption to microporous filters, we found that the enhanced adsorption was associated with indirect effects rather than direct effects. The increase in viral adsorption observed when aluminum chloride was added to water was related to the decrease in the pH of the water. Similar results could be obtained by adding HCl. The increased adsorption of viruses in water at pH 7 following addition of aluminum chloride was probably due to flocculation of aluminum, since removal of flocs by filtration greatly reduced the enhancement observed. The only direct effect of aluminum chloride on virus adsorption that we observed was interference with adsorption to microporous filters. Under conditions under which hydrophobic interactions were minimal, aluminum chloride interfered with virus adsorption to Millipore, Filterite, and 1MDS filters. In most cases, less than 10% of the viruses adsorbed to filters in the presence of a multivalent salt and a compound that interfered with hydrophobic interactions (0.1% Tween 80 or 4 M urea).

Adsorption↗
PubMed1998

Isolation of an amoeba naturally harboring a distinctive Legionella species.

There are numerous in vitro studies documenting the multiplication of Legionella species in free-living amoebae and other protozoa. It is believed that protozoa serve as host cells for the intracellular replication of certain Legionella species in a variety of environmental settings. This study describes the isolation and characterization of a bacterium initially observed within an amoeba taken from a soil sample. In the laboratory, the bacterium multiplied within and was highly pathogenic for Acanthamoeba polyphaga. Extracellular multiplication was observed on buffered charcoal yeast extract agar but not on a variety of conventional laboratory media. A 16S rRNA gene analysis placed the bacterium within the genus Legionella. Serological studies indicate that it is distinct from previously described species of the genus. This report also describes methods that should prove useful for the isolation and characterization of additional Legionella-like bacteria from free-living amoebae. In addition, the characterization of bacterial pathogens of amoebae has significant implications for understanding the ecology and identification of other unrecognized bacterial pathogens.

Amoeba↗
PubMed1998

Dynamic susceptibility contrast MR imaging of regional cerebral blood volume in Alzheimer disease: a promising alternative to nuclear medicine.

BACKGROUND AND PURPOSE: The goal of our study was to evaluate the sensitivity and specificity for Alzheimer disease of semiquantitative dynamic susceptibility contrast (DSC) MR imaging as compared with results of qualitative single-photon emission computed tomography (SPECT) in the same patients and with previously published semiquantitative SPECT results. METHODS: Fifty subjects were studied: 19 patients with probable Alzheimer disease with moderate cognitive impairment, eight mildly impaired patients with possible or probable Alzheimer disease, 18 group-matched elderly healthy comparison subjects, and five elderly comparison patients with psychiatric diagnoses. Relative values of temporoparietal regional cerebral blood volume (rCBV) were measured as a percentage of cerebellar rCBV, and group classification was assessed with logistic regression. The DSC MR imaging results were compared with SPECT scans in these same subjects and with previously published semiquantitative SPECT data. RESULTS: Temporoparietal rCBV ratios were reduced 20% bilaterally in the patients with Alzheimer disease. Using left and right temporoparietal rCBV as index measures, sensitivity was 95% in moderately affected patients with Alzheimer disease and 88% in patients with mild cases. Specificity was 96% in healthy comparison subjects and in psychiatric comparison subjects. Sensitivity with DSC MR imaging was considerably better than with visual clinical readings of SPECT scans (74% in moderate and 50% in mild Alzheimer disease cases), and was similar to previous published SPECT temporoparietal measurements (90%). Specificity with SPECT was 100% visually and 87% based on previous temporoparietal measurements. CONCLUSIONS: DSC MR imaging of rCBV is promising as a safe, potentially lower-cost alternative to nuclear medicine imaging for the evaluation of patients with dementia.

Adult↗
PubMed1997

Vascular innervation in atherogenesis.

Although collar-induced atherosclerosis continues to be used as an investigative tool, the underlying mechanism has not been established. Two primary mechanisms suggested are adventitial ischemia due to reduction in vasa vasorum, and perivascular denervation. We have examined the effect of injuring the common carotid artery in the pattern produced by the ends of a silastic collar, and have correlated the effect on innervation with change in intima/media ratios in normal and cholesterol-fed rabbits. The serum cholesterol of cholesterol-fed rabbits was significantly elevated by 10 days following initiation of cholesterol feeding, and further elevated at 21 days. No structural difference was detected between the uninjured carotid arteries of control and cholesterol-fed rabbits. At the site of injury in freeze injured carotid arteries there was a thickening of the intima which was increased in cholesterol-fed rabbits. The intima at the site of injury was composed of lipid-laden cells embedded in a matrix of collagen and elastin fibres. In carotid artery segments, between two sites of freeze injury, denervation was established by immunohistochemistry and electron microscopy. The denervated segments were not morphologically different from uninjured carotid arteries in either control or cholesterol-fed rabbits. While injury induced intimal thickening and foam cell development, denervation did not. It is concluded that perivascular denervation is a consequence of silastic collar application and is not involved in the induction of atherosclerosis.

Animals↗
PubMed1996

Severe cardiovascular disease and Alzheimer's disease: senile plaque formation in cortical areas.

The main objectives of this study were to analyze the distribution of senile plaques (SP) and neurofibrillary tangles (NFT) in different cortical areas of patients suffering from severe cardiovascular diseases (CVD) and to compare them with Alzheimer's disease (AD) cases. Forty brains were divided into three groups: an AD group (n = 12), a CVD group (n = 17), and a nonheart disease control group (n = 11). The cortical areas examined were the middle frontal gyrus, the superior and inferior watershed areas, the hippocampal formation with the transentorhinal cortex, and the primary visual cortex. SP and NFT were counted in Bielschowsky-stained sections from all cortical areas and from the hippocampal formation and the transentorhinal cortex, respectively. Patients with severe CVD occupied an intermediate position in the spectrum of SP formation between AD and nonheart disease patients. The CVD group showed a higher prevalence of SP than the control group, and SP counts were significantly larger in the inferior watershed area, dentate gyrus, subiculum, and transentorhinal cortex. The distribution of SP was similar in CVD and AD patients. Control and CVD patients showed no difference regarding the number of NFT. The existence of a possible cardiovascular component in the genesis of SP is discussed.

Aged↗
PubMed1996

Dynamic susceptibility contrast MRI of regional cerebral blood volume in Alzheimer's disease.

OBJECTIVE: The purpose of this study was to investigate the potential effectiveness of dynamic susceptibility contrast magnetic resonance imaging (MRI) to discriminate elderly patients with Alzheimer's disease from normal matched comparison subjects. METHOD: Images of regional cerebral blood volume (CBV) were generated from echo-planar MRI with the dynamic susceptibility contrast method in 13 Alzheimer's disease patients and 13 comparison subjects group-matched on age and gender. RESULTS: Temporoparietal cerebral blood volume, expressed as a percentage of the cerebellum value, was reduced 17% bilaterally in the patients with Alzheimer's disease. Blood volume in sensorimotor regions was reduced only 8.5% in the patients. Discriminant function analysis based on left and right temporoparietal measures correctly classified 88.5% of the subjects as patients or comparison subjects. Temporoparietal CBV was reduced even in mildly affected Alzheimer's disease patients (Mini-Mental State scores > 24). CONCLUSIONS: Dynamic susceptibility contrast MRI of regional CBV is promising as a nonradioactive, potentially lower-cost alternative to other functional neuroimaging methods for evaluating Alzheimer's disease.

Aged↗
PubMed1995

Deficits in short-term memory in adult survivors of childhood abuse.

Exposure to stress has been associated with alterations in memory function, and we have previously shown deficits in short-term verbal memory in patients with a history of exposure to the stress of combat and the diagnosis of posttraumatic stress disorder (PTSD). Few studies of any kind have focused on adult survivors of childhood physical and sexual abuse. The purpose of this study was to investigate short-term memory function in adult survivors of childhood abuse. Adult survivors of severe childhood physical and sexual abuse (n = 21), as defined by specific criteria derived from the Early Trauma Inventory (ETI), who were presenting for psychiatric treatment were compared with healthy subjects (n = 20) matched for several variables including age, alcohol abuse, and years of education. All subjects were assessed with the Wechsler Memory Scale (WMS) Logical (verbal memory) and Figural (visual memory) components, the Verbal and Visual Selective Reminding Tests (SRT), and the Wechsler Adult Intelligence Scale-Revised (WAIS-R). Adult survivors of childhood abuse had significantly lower scores on the WMS Logical component for immediate and delayed recall in comparison to normal subjects, with no difference in visual memory, as measured by the WMS or the SRT, or IQ, as measured by the WAIS-R. Deficits in verbal memory, as measured by the WMS, were associated with the severity of abuse, as measured by a composite score on the ETI. Our findings suggest that childhood physical and sexual abuse is associated with long-term deficits in verbal short-term memory. These findings of specific deficits in verbal (and not visual) memory, with no change in IQ, are similar to the pattern of deficits that we have previously found in patients with combat-related PTSD.

Adult↗
PubMed1995

Effect of denervation of the rat superior mesenteric arterial bed on the distribution of resistance among the first four orders of branching.

The rat superior mesenteric artery with its first four orders of branching has been examined as an isolated perfused preparation. Lumen diameter and proportional resistance at each level have been determined and compared under conditions of constant pressure following methoxamine-induced constriction and acetylcholine-induced relaxation in intact and denervated preparations. A comparison was also made between intact preparations under conditions of constant pressure and constant flow. Lumen diameter and segment length were measured by analysis of video-taped images. The distribution of resistance among the first four orders of branching was estimated from the measured values using the Poiseuille formula. Intact first and fourth order branches had a proportionately low resistance, with the remaining resistance being fairly evenly distributed between the second and third order branches. No change in the pattern occurred as a result of either methoxamine or acetylcholine treatment. The pattern of distribution of resistance changed following denervation, so that proportional resistance was high in the first order branches and fell off from the second to fourth order branches. With methoxamine, the first order branches of denervates had a significantly higher resistance than in intact tissues, with the distribution of resistance in the second to fourth order branches following the basal resistance pattern. Reduction in the proportion of resistance with acetylcholine was similar in both intact and denervated preparations. Distribution of resistance did not differ between constant flow and constant pressure intact preparations.

Acetylcholine↗
PubMed1995

MRI-based measurement of hippocampal volume in patients with combat-related posttraumatic stress disorder.

OBJECTIVE: Studies in nonhuman primates suggest that high levels of cortisol associated with stress have neurotoxic effects on the hippocampus, a brain structure involved in memory. The authors previously showed that patients with combat-related posttraumatic stress disorder (PTSD) had deficits in short-term memory. The purpose of this study was to compare the hippocampal volume of patients with PTSD to that of subjects without psychiatric disorder. METHOD: Magnetic resonance imaging was used to measure the volume of the hippocampus in 26 Vietnam combat veterans with PTSD and 22 comparison subjects selected to be similar to the patients in age, sex, race, years of education, socioeconomic status, body size, and years of alcohol abuse. RESULTS: The PTSD patients had a statistically significant 8% smaller right hippocampal volume relative to that of the comparison subjects, but there was no difference in the volume of other brain regions (caudate and temporal lobe). Deficits in short-term verbal memory as measured with the Wechsler Memory Scale were associated with smaller right hippocampal volume in the PTSD patients only. CONCLUSIONS: These findings are consistent with a smaller right hippocampal volume in PTSD that is associated with functional deficits in verbal memory.

Adult↗
PubMed1994

A case-based anatomy course.

A course is described in which the students give consideration to clinical cases as they review their current knowledge, and follow a set protocol which guided them in preparing their learning. The students are required to examine a case history, put down as key words either their first answer or the knowledge they consider they would need to answer specific questions. They then select stations at which additional information, wet specimens, models and radiological images assist them in upgrading their knowledge. They complete the exercise by writing a final answer to the questions on the case. The tutor is able through examination of the key words to determine the knowledge of the students as they enter, and confirm appropriate learning by inspection of the final answer. The students are able to identify their own deficiencies, develop strategies for thinking and learning, resulting in the acquisition of expertise in problem solving, and extend their communication skills by working with colleagues. While the course was designed for second-year anatomy teaching it could be applied to other disciplines.

Anatomy↗
PubMed1994

The involvement of CGRP in acetylcholine-induced vascular relaxation.

Earlier work on peptidergic fibres suggested some involvement of CGRP perivascular nerve fibres in acetylcholine-induced endothelium-dependent vascular relaxation. We have investigated the effect of blocking CGRP receptors and CGRP replacement on acetylcholine-induced endothelium-dependent vascular relaxation in the isolated perfused mesenteric arterial bed in normal Sprague-Dawley rats and in rats seven days following freeze-denervation of the superior mesenteric artery. Freeze-denervation was carried out under pentobarbital anesthesia (40 mg/Kg). It was found that the ability of acetylcholine to cause relaxation was reduced by CGRP receptor blocking with CGRP8-37 in vessels from control rats, but returned to pre-blocking levels after washout of the antagonist. Treatment with CGRP increased the relaxation due to acetylcholine in denervated vessel beds, but not in control tissues. The CGRP receptor appears to be involved in the acetylcholine-induced relaxation of blood vessels. The mechanism of action is not known, although both acetylcholine and CGRP, act through activation of K+ channels, and CGRP may facilitate the activation of K+ channels by acetylcholine.

Acetylcholine↗
PubMed1994

The involvement of perivascular innervation in acetylcholine-induced endothelium-dependent vascular relaxation in the rat superior mesenteric arterial bed.

The distribution of the ability of perivascular peptidergic innervation to influence acetylcholine-induced relaxation in the arterial bed has been investigated using the superior mesenteric arterial bed of the rat. The superior mesenteric artery was denervated by freezing, under pentobarbital anaesthesia (40 mg/kg i.p.), at one of two different points and the animals allowed to survive for 7, 14, 21 or 28 days following freezing. This produced a range of denervation along the superior mesenteric artery and its branches. The ability to respond to acetylcholine in an endothelium-dependent fashion was determined pharmacologically in isolated perfused superior mesenteric artery preparations. The extent of the denervation was determined by immunohistochemistry. It was found that the ability of the arterial bed to relax in a concentration-dependent manner to increasing concentrations of acetylcholine was little altered by denervation of the superior mesenteric artery alone. However when a short piece of the superior mesenteric artery and its primary branches were denervated the response to acetylcholine was reduced. It is concluded that the innervation of the primary branches of the mesenteric artery, the jejunal and ileal branches, contributes to the ability of acetylcholine to cause endothelium-dependent relaxation.

Acetylcholine↗