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Biomedical subjects

J A Morgan

Publications and source records attributed to J A Morgan.

At least 73 records · Page 4Linked to original sources
PubMed1991

Survival of Aeromonas salmonicida in lake water.

The survival of Aeromonas salmonicida subsp. salmonicida in lake water was investigated by using a variety of techniques. They included acridine orange epifluorescence, respiration, cell culture, cell revival, flow cytometry, plasmid maintenance, and membrane fatty acid analysis. During a 21-day study, A. salmonicida became nonculturable in sterile lake water samples. Flow cytometry and direct microscopy indicated that cells were present. Although the nonculturable cells could not be revived, the recovery method did indicate that the presence of low numbers of culturable cells within samples could produce misleading results. Plasmid DNA, genomic DNA, and RNA were maintained in the nonculturable cells; in addition, changes in the fatty acid profiles were also detected. Although viability could not be proven, it was shown that the morphological integrity of nonculturable cells was maintained.

Aeromonas↗
PubMed1991

Use of a xylE marker gene to monitor survival of recombinant Pseudomonas putida populations in lake water by culture on nonselective media.

IncQ marker plasmids were previously constructed to enable the analysis of the survival of populations of Pseudomonas putida released into lake water (C. Winstanley, J. A. W. Morgan, R. W. Pickup, J. G. Jones, and J. R. Saunders, Appl. Environ. Microbiol. 55:771-777, 1989). We constructed equivalent IncP plasmids, pLV1016 and pLV1017, to provide conjugative alternative systems. Detection of the xylE gene carried by marker plasmids was found to be a valid indicator to use for studying the survival of released populations by culturing on nonselective media. These plasmids were used to study the survival of populations of Pseudomonas putida in both sterile and untreated lake water. The effects of inoculum size, the metabolic burden imposed on the cell by the unregulated expression of xylE, and an auxotrophic mutation carried by the host strain were studied. We also assessed the reproducibility and hence the predictability of the survival of released populations. Model systems with a single lake water sample and model systems with three different lake water samples, taken from the same site in consecutive months, were used to analyze variability between replicates and to assess differences caused by host strain or water sample. A large variability was found depending on which water sample was used. These findings imply that it will be difficult to predict accurately the survival of released populations in the natural environment.

Catechol 2,3-Dioxygenase↗
PubMed1991

Molecular biology: new tools for studying microbial ecology.

The general aim of studies in microbial ecology is to determine the activities of particular groups of organisms in the natural environment. Current developments in molecular biology are providing methods that can be adopted for investigations in microbial ecology. Presently, molecular techniques are being used to determine population and community structures in samples. Following on from this, methods are needed to determine the activities of these organisms in their natural state. This review describes the application of molecular techniques to the study of micro-organisms in environmental samples.

Bacteria↗
PubMed1990

Morphology of rat exocrine pancreas prepared by anhydrous cryo-procedures.

This paper describes and compares the morphology of a relatively complex tissue, the exocrine pancreas, prepared by state-of-the-art anhydrous cryoprocedures. Cryopreparative procedures are being used increasingly for a wide range of applications, for example, electron-probe x-ray microanalysis and immunocytochemical localization of antigenic molecules, because they preserve the composition of the specimen better than procedures involving aqueous media. Some doubts have remained concerning the morphology of cryosections and the precise identification of subcellular structures. We show that thin and sufficiently large cryosections of fresh biological tissues can be produced using commercially available hardware. The freeze-dried cryosections display high intrinsic contrast, are stable under the beam, and allow identification of intracellular fine structure.

Animals↗
PubMed1989

Presentations of acute phenytoin overdose.

A 15-year-old boy ingested 19.6 g (15 g verifiable) phenytoin sodium approximately four hours before emergency department presentation. The patient survived the suicide attempt with only supportive care, despite the ingestion of 392 mg/kg and a peak serum level of 100.8 micrograms/mL. A wide spectrum of physical findings consistent with acute massive ingestion of phenytoin was noted. This case report and a review of cases reported in the English literature of acute single anticonvulsant ingestion further delineate the clinical presentation of acute phenytoin overdose.

Adolescent↗
PubMed1989

The diagnosis, therapy and prognosis of diffuse malignant mesothelioma.

Between 1969 and 1985, 245 patients with diffuse malignant mesothelioma were treated (157 male, 88 female). The average age was 55.8 years and the sex ratio was 1.8:1 in favour of males. The right side was more frequently affected than the left (56.7% vs. 43.3%). A pleural effusion and dyspnoea were the presenting signs and symptoms in 83.7% of the patients and unilateral chest pain in 64.2%. Noninvasive diagnostic procedures included a chest X-ray and computed tomography of the thorax. Pleural effusion and pleural thickening were detected most frequently. Malignant cells were identified by pleural fluid cytology in 45.3% and by needle biopsy of the pleura in 42.7% of the patients. Forty-five patients were treated conservatively and 200 patients underwent operation: diagnostic thoracotomy (78); partial pleurectomy (72); total pleurectomy (46); extended pleuropneumonectomy (2); partial removal of the diaphragm (1) and total pleurectomy and upper lobectomy (1). The perioperative mortality was 6%. The conservative and postoperative treatment depended on the patients' symptoms and included radiotherapy and chemotherapy alone or in combination. The mean survival time of the 222 non-survivors was 9.2 months. After 1 year, 36% of the patients were still alive, after 2 years, 10.8% and the 5-year survival was 4.1%. The median survival time in patients treated non-operatively was 6 months--a little over half that of the patients treated surgically (10.1 months).

Adult↗
PubMed1989

Direct phenotypic and genotypic detection of a recombinant pseudomonad population released into lake water.

As a system for studying the fate of genetically engineered microorganisms in the environment, we have previously constructed recombinant plasmids encoding a xylE marker gene (C. Winstanley, J. A. W. Morgan, R. W. Pickup, J. G. Jones, and J. R. Saunders, Appl. Environ. Microbiol. 55:771-777, 1989). A series of direct membrane filter methods have been developed which facilitate the detection of bacterial cells harboring the xylE gene, its product, catechol 2,3-dioxygenase, and catechol 2,3-dioxygenase enzyme activity directly from water samples. These methods enable detection of recombinant populations at concentrations as low as 10(3) to 10(4) cells ml of lake water-1. Direct detection facilitates ecological studies of a range of bacterial strains containing the marker system in aquatic environments. The fate of a recombinant pseudomonad population in lake water was assessed by a combination of colony-forming ability, direct counts, and direct detection of the xylE gene and phenotypic expression of its product.

Blotting, Western↗
PubMed1989

Differential regulation of lambda pL and pR promoters by a cI repressor in a broad-host-range thermoregulated plasmid marker system.

Plasmid systems with unique markers were constructed to assess the fate of recombinant DNA and genetically manipulated bacteria in soil and freshwater model environments. On such constructs the marker gene, xylE (for catechol 2,3-dioxygenase), is expressed from the lambda promoter pL or pR, each of which is controlled by the temperature-sensitive lambda repressor c1857. Combinations of these elements were cloned into the broad-host-range plasmid pKT230 to form pLV1010 (pL-xylE), pLV1011 (pL-xylE-c1857), and pLV1013 (pR-xylE-c1857). The recombinant plasmids were introduced into different gram-negative bacteria. The thermoregulated system of pLV1013 functioned well in a range of species, with xylE induction being readily achieved by elevation of the temperature from 28 to 37 degrees C. There was a difference in the induction of catechol 2,3-dioxygenase activity, depending on whether xylE was expressed from pL (pLV1011) or pR (pLV1013). Our observations on testing the different systems in a number of hosts suggest that genes carried by the DNA of genetically engineered microorganisms may not be expressed in a predictable manner following transfer from the release host to other species.

Catechol 2,3-Dioxygenase↗
PubMed1989

Immunological reaction against the aging human subarachnoid erythrocyte. A model for the onset of cerebral vasospasm after subarachnoid hemorrhage.

The role of the aging human erythrocyte in the mechanisms leading to cerebral vasospasm after subarachnoid hemorrhage was investigated using an in vitro model for the environment of the erythrocyte in a subarachnoid blood clot. It has long been suspected that, due to its potent vasoactivity, erythrocyte lysate provides the major vasoconstrictive input to cerebral arteries during vasospasm. Under the model conditions (incubation at 37 degrees C in an artificial cerebrospinal fluid), however, the rate of spontaneous hemolysis was quite slow (about 1%/day), becoming only somewhat more rapid after 4 days' incubation. The rate of hemolysis of aging erythrocytes was dramatically increased (500- to 1000-fold) by the addition of plasma proteins, but only after the erythrocytes had aged 2 to 3 days, or more. The mechanism of age-dependent, plasma-induced hemolysis of originally autologous erythrocytes is shown to involve activation of the plasma complement protein pathway, analogous to the mechanisms of innate immunity which lead to lysis of nonautologous cell types and activate the inflammatory response.

Aging↗
PubMed1989

[Pulse oximetry monitoring of single lung anesthesia in non-cardiac thoracic surgery].

The pulse oximeter provides continuous and non-invasive measurement of the arterial oxygen saturation. Pulse oximetry contributes to safer patient management because of the immediate availability of oxygen saturation values. This is particularly important in high-risk anaesthesia such as one-lung anaesthesia. Pulse oximetry is as important as ECG monitoring and invasive blood pressure monitoring and should therefore be a standard monitoring technique in thoracic surgery. With a pulse oximeter it is possible to efficiently monitor anaesthesia during one lung ventilation thereby avoid hypoxia with its life-threatening complications.

Adult↗
PubMed1988

Scalp laceration repair without prior hair removal.

The effect on the infection rate of hair removal prior to scalp laceration repair has not been studied prospectively in the outpatient setting. Concern exists that not removing skin hair may lead to an increased incidence of serious wound infections. Sixty-eight scalp lacerations were repaired without hair removal and examined prospectively for infection. No infections were noted at 5-day follow-up. The mean patient age was 21.8 +/- 19.8 years, and the mean laceration length was 2.5 +/- 2.0 cm. The mean time from injury to repair of laceration was 2.2 +/- 2.8 hours. Sixty-three lacerations (92.7%) were repaired within 3 hours of injury. A prospective, randomized study in a select patient population to examine the effect of prior hair removal on infection rate is warranted.

Adolescent↗
PubMed1986

False aneurysm of the descending thoracic aorta caused by an inhaled foreign body. A case report.

A case of traumatic false aneurysm of the descending thoracic aorta is reported. The aneurysm was caused by the inhalation of a needle into the left main bronchus. The diagnosis of a false aneurysm was made 42 days after inhalation. The aneurysm was repaired by direct suture without the need for circulatory assistance or a shunt. There were no intra- or postoperative complications.

Adolescent↗
PubMed1986

Testicular torsion following orchiopexy.

A case of testicular torsion one year after orchiopexy is presented. The occurrence of testicular torsion following surgery is a rare event which has the potential for diagnostic misadventures. To better delineate this condition, we performed a literature review of all reported cases of recurrent testicular torsion. Thirteen reported patients with testicular torsion following orchiopexy are presented and discussed.

Adult↗