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Biomedical subjects

J A Hanson

Publications and source records attributed to J A Hanson.

At least 19 recordsLinked to original sources
PubMed1999

The R-type pyocin of Pseudomonas aeruginosa C is a bacteriophage tail-like particle that contains single-stranded DNA.

Pseudomonas aeruginosa R-type pyocin particles have been described as bacteriocins that resemble bacteriophage tail-like structures. Because of their unusual structure, we reexamined whether they contained nucleic acids. Our data indicated that pyocin particles isolated from P. aeruginosa C (pyocin C) contain DNA. Probes generated from this DNA by the random-primer extension method hybridized to distinct bands in restriction endonuclease-digested P. aeruginosa C genomic DNA. These probes also hybridized to genomic DNA from 6 of 18 P. aeruginosa strains that produced R-type pyocins. Asymmetric PCR, complementary oligonucleotide hybridization, and electron microscopy indicated that pyocin C particles contained closed circular single-stranded DNA, approximately 4.0 kb in length. Examination of total intracellular DNA from mitomycin C-induced cultures revealed the presence of two extrachromosomal DNA molecules, a double-stranded molecule and a single-stranded molecule, which hybridized to pyocin DNA. Sequence analysis of 7,480 nucleotides of P. aeruginosa C chromosomal DNA containing the pyocin DNA indicated the presence of pyocin open reading frames with similarities to open reading frames from filamentous phages and cryptic phage elements. We did not observe any similarities to known phage structural proteins or previously characterized pseudomonal prt genes expressing R-type pyocin structural proteins. These studies demonstrate that pyocin particles from P. aeruginosa C are defective phages that contain a novel closed circular single-stranded DNA and that this DNA was derived from the chromosome of P. aeruginosa C.

Amino Acid Sequence↗
PubMed1997

Characterization of highly radiosensitive cell lines from a human ovarian small-cell cancer.

Cells were obtained at paracentesis from a patient with a rapidly growing ovarian tumor. A monolayer cell line (V7S), a xenograft tumor line (V7), and subsequently a xenograft-derived monolayer cell line (V7M) were established. Histological and immunohistochemical studies of the original tumor, xenograft, and cell lines provided a diagnosis of small-cell carcinoma of the ovary-which is consistent with the clinical course of the patient. V7S and V7M had a predominantly hypodiploid karyotype with a small tetraploid population. The V7M, which has been in long-term culture, also showed a nonrandom translocation involving chromosomes 1 and 14 and monosomy of X. Radiobiologically, V7S, V7, and V7M showed marked radiosensitivity with surviving fractions at 2 Gy, measured by clonogenic assay, of between 0.022 and 0.147. Split-dose experiments provided evidence that this radiosensitivity was not due to an inability in cellular repair. In vivo data from the xenograft (V7) revealed a highly radiosensitive tumor, corroborating the in vitro studies.

Carcinoma, Small Cell↗
PubMed1997

Staging intrathoracic non-small-cell lung cancer.

This article outlines the ability of imaging techniques to stage intrathoracic non-small-cell lung cancer, particularly the extent of primary tumour (T stage), and the presence of nodal metastases (N stage). The detection of hilar and mediastinal lymph-node metastases by CT is covered initially, followed by an appraisal of MRI and radionuclide imaging techniques. Finally, the evaluation of mediastinal and chest-wall invasion by CT and MRI is described, and note is made of developing applications of ultrasound and endosonography. Computed tomography remains the standard technique, but its limitations are discussed, as is the value of other complementary imaging techniques.

Carcinoma, Non-Small-Cell Lung↗
PubMed1997

Determination of radiosensitivity in established and primary squamous cell carcinoma cultures using the micronucleus assay.

In this study, the cytokinesis-block micronucleus assay (CBMN) was used to measure radiosensitivity in three established cell lines (SCC-61, V175 and V134) and 10 primary cell cultures of squamous cell carcinoma (SCC) of the head and neck. Assessment involved optimisation of the assay to determine cytochalasin-B (CB) concentration and sampling time postirradiation. A much closer correlation between dose-response data measured in the clonogenic and micronucleus assays was found when the micronucleus assay was performed under standardised conditions for each cell line (2 micrograms/ml CB: 48 h postirradiation) instead of predetermined optimised assay conditions. This indicates that, for these SCC cell lines, the CBMN assay may be able to predict in vitro radiosensitivity. To be of clinical use in predicting radiosensitivity, the CBMN assay also needs to be evaluated with primary cell cultures. In this study, no relationship between micronucleus frequency at 2 or 6 Gy and patient clinical outcome 12 months following surgery and radiotherapy was seen. Similarly, no association between patient outcome and tumour stage, nodal stage and histology was observed. These CBMN assay data from the primary cell cultures are presently inconclusive as a measure of patient tumour radiosensitivity.

Carcinoma, Squamous Cell↗
PubMed1997

The influence of experience on the reliability of goniometric and visual measurement of forefoot position.

Goniometric measurement of forefoot position relative to the rearfoot is a routine procedure used by rehabilitation specialists. This measurement is also frequently made by visual estimation. The influence of tester experience on the reliability of these two techniques at the forefoot is unknown. The purpose of this investigation was to directly examine the reliability of goniometric and visual estimation of forefoot position measurements when experienced and inexperienced testers perform the evaluation. Two clinicians (> or = 10 years experience) and two physical therapy students were recruited as testers. Ten subjects (20-31 years old), free from pathology, were measured. Each foot was evaluated twice with the goniometer and twice with visual estimation by each tester. Intraclass correlation coefficient (ICC) and coefficients of variation method error were used as estimates of reliability. There was no dramatic difference in the intratester or intertester reliability between experienced and inexperienced testers, regardless of the evaluation used. Estimates of intratester reliability (ICC 2,1), when using the goniometer, ranged from 0.08 to 0.78 for the experienced examiners and from 0.16 to 0.65 for the inexperienced examiners. When using visual estimation, ICC (2,1) values ranged from 0.51 to 0.76 for the experienced examiners and 0.53 to 0.57 for the inexperienced examiners. The estimate of intertester reliability [ICC (2,2)] for the goniometer was 0.38 for the experienced examiners and 0.42 for the inexperienced examiners. When using visual estimation, ICC (2,2) values were 0.81 for the experienced examiners and 0.72 for the inexperienced examiners. Although experience does not appear to influence forefoot position measurements, of the two evaluation techniques, visual estimation may be the more reliable.

Adult↗
PubMed1996

Magnetic resonance imaging of adrenocortical adenomas in childhood: correlation with computed tomography and ultrasound.

There are few descriptions of the magnetic resonance (MR) appearance of hyperfunctioning adrenocortical tumours, particularly those occurring in childhood. We studied five patients, two girls and three boys, aged 6-14.3 years, presenting with clinical syndromes of adrenocortical hyperfunction. The diagnoses were Cushing's syndrome (n = 2), virilisation (n = 2), and Conn's syndrome (n = 1). Biochemical features suggested an adrenal lesion in each case. MR and ultrasound were performed in all five cases, with CT in four. Each patient had a functional adrenal tumour secreting either cortisol, androgens or aldosterone alone, or a combination of cortisol, androgens and oestradiol. The histological diagnosis was adenoma in four cases and tumour of indeterminate nature in one case. MR clearly showed the tumours (diameter 1.0-7.5 cm), all the lesions being of high signal intensity relative to liver on T2-weighted sequences. CT revealed an adrenal mass in each of the four patients scanned, three of which enhanced after intravenous contrast medium injection. The multiplanar imaging of MR allowed better distinction from adjacent structures and also demonstrated an unenlarged contralateral adrenal gland. In the patient with a 1-cm Conn's adenoma the lesion was more easily seen on MR than CT. Ultrasound showed the four larger tumours but was unable to visualise the contralateral adrenal or the Conn's adenoma. In conclusion, the MR appearances of four adrenocortical adenomas and one indeterminate tumour in children are described. MR has been found to be at least equal to CT in the detection of these tumours, with some possible advantages. Both techniques are superior to ultrasound.

Adenoma↗
PubMed1996

The role of computed tomography in evaluation of subchondral osseous lesions in seven horses with chronic synovitis.

Seven horses with severe, persistent lameness of sudden onset were evaluated with scintigraphy and/or computed tomography. The lameness was localised to the front fetlock joint in 2 horses and to the tibiotarsal joint in 5 horses. Five of the horses had a history of intra-articular injections of the involved joint prior to presentation. All horses had effusion of the affected joint and were positive to flexion tests. Intraarticular anaesthesia eliminated or improved the lameness in 4 cases and a nerve conduction block proximal to the affected joint improved the lameness in another. Cytology examination of fluid from affected joints identified normal joint fluid (one horse) or elevations in nucleated cell counts of 0.9 x 10(9)/l-36.8 x 10(9)/l and total protein 20-42 g/l (6 horses). The joint fluid of 2 of these horses cultured positive for bacteria. Initial radiographs were either normal (4 cases) or the changes seen were not sufficient to explain the degree of lameness. In the 6 cases where scintigraphy was performed, intense focal isotope uptake was found in the suspected region, which corresponded to the proximal portion of the first phalanx (2 cases), distal tibia (2 cases), or talus (3 cases). Computed tomography (CT) was performed because occult fracture or osteomyelitis was suspected; and knowledge of the precise anatomical location of the lesion was considered necessary to assess the need for surgery and to plan the surgical approach. Hypodense focal lesions with hyperdense haloes were found in the subchondral bone deep to the sagittal groove of the first phalanx (P1) (2 cases) in the cochlea of the distal tibia (2 cases), and in the intertrochlear portion of the talus (3 cases). Communication between the lesion and the joint space was demonstrated by CT in 5 cases. Post mortem examination of one case revealed synovitis and a chronic bone abscess (Brodie's abscess) communicating with the joint space.

Animals↗
PubMed1996

Myasthenia gravis presenting with stridor.

The case is described of a 72 year old woman who presented with a two year history of exertional stridor in whom the diagnosis of myasthenia gravis was delayed. Although an uncommon cause, myasthenia gravis should be included in the differential diagnosis of stridor.

Aged↗
PubMed1995

The sensitivity of chronic lymphocytic leukaemia lymphocytes to irradiation in vitro.

The inhibition of [3H]-thymidine incorporation into the DNA of mitogen-stimulated chronic lymphocytic leukaemia lymphocytes by chlorambucil or gamma-irradiation in vitro was measured in a series of patients, some of whom were untreated, some treated and some who were showing resistance to first-line or second-line treatment. There was evidence of resistance to irradiation developing in parallel with that to chlorambucil. The resistance to chlorambucil in chronic lymphocytic leukaemia (CLL) is not necessarily due to altered drug transport or metabolism but to a more fundamental process affecting DNA damage.

Antineoplastic Agents, Alkylating↗
PubMed1995

Determination of radiation-induced damage in lymphocytes using the micronucleus and microgel electrophoresis 'Comet' assays.

DNA damage assays may be useful as rapid predictors of normal tissue radiosensitivity in clinical samples. We measured in vitro radiation-induced (2 Gy) damage to lymphocytes from cancer patients and normal healthy donors using both the micronucleus and microgel electrophoresis (Comet) assays simultaneously. For damage assessment, there was a good correlation (P < 0.001) between the mean comet lengths and the fraction of cells with comets. There was no correlation with initial damage, determined as the proportion of cells within a sample that formed comets, in comparison with the mean frequency of micronuclei per binucleate cell. However, there appeared to be an association between the determination of repair proficiency in the Comet assay and the mean frequency of micronuclei per binucleate cell in lymphocytes from cancer patients.

DNA↗
PubMed1995

The micronucleus assay: an evaluation of its use in determining radiosensitivity in vitro.

The cytokinesis-block micronucleus assay was used to measure radiosensitivity in vitro in a panel of seven cell lines. Six of these cell lines were used to study the major parameters of this assay. We observed varying sensitivities following cytochalasin-B exposure. Treatment with 1 microgram/ml cytochalasin-B for 24 h reduced cell survival in four of the six cell lines by > 60%. Cytochalasin-B concentration and post-irradiation culture time were both found to influence cell-response. In three cell lines (V39, V134 and HX142), a decrease in cytochalasin-B concentration (2-0.5 microgram/ml) resulted in an increase in the frequency of radiation-induced micronuclei per binucleate cell. In other cell lines, either the opposite (V7M, CHO-K1) or no effect (WiDr) was seen. A linear dose-response was observed between induced damage expressed as the frequency of micronuclei and radiation dose in all but one melanoma (V39) cell line. Evidence for radiation-induced division-delay, with the maximum frequency of binucleation in irradiated cultures occurring 24-48 h after that of controls, was only seen in two cell lines. Of particular note, and in contrast to some other published reports, was the lack of a general correlation between cell-response measured in the clonogenic and the cytokinesis-block micronucleus assays. Consideration of lethal lesions, determined from the clonogenic dose-response curve, with respect to micronucleus frequency showed a complex relationship, with one micronucleus per binucleate cell corresponding to a wide range of lethal lesions depending on the cell line.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1994

Aortic root thrombus causing stroke in a patient with systemic lupus erythematosus.

We report on a 24 year old woman with systemic lupus erythematosus (SLE) who presented with a cerebrovascular accident affecting her right side. Unusually, this was associated with an aortic root thrombus with absence of any commonly recognised thrombophilic features. Following removal of the thrombus and anticoagulation, she made a good recovery. The relationship between valvular problems and cerebral lesions in SLE is discussed.

Adult↗
PubMed1993

Organoapatites: materials for artificial bone. II. Hardening reactions and properties.

This article reports on chemical reactions and the properties they generated in artificial bone materials termed "organoapatites." These materials are synthesized using methodology we reported in the previous article of this series. Two different processes were studied here for the transition from organoapatite particles to implants suitable for the restoration of the skeletal system. One process involved the hardening of powder compacts by beams of blue light derived from a lamp or a laser and the other involved pressure-induced interdiffusion of polymers. In both cases, the hardening reaction involved the formation of a polyion complex between two polyelectrolytes. In the photo-induced reaction an anionic electrolyte polymerizes to form the coulombic network and in the pressure-induced one, pressure forms the complex by interdiffusion of two polyions. Model reactions were studied using various polycations. Based on these results the organoapatite selected for the study was that containing dispersed poly(L-lysine) and sodium acrylate as the anionic monomer. The organomineral particles can be pressed at room temperature into objects of great physical integrity and hydrolytic stability relative to anorganic controls. The remarkable fact about these objects is that intimate molecular dispersion of only 2-3% by weight organic material provides integrity to the mineral network in an aqueous medium and also doubles its tensile strength. This integrity is essentially nonexistent in "anorganic" samples prepared by the same methodology used in organoapatite synthesis. The improvement in properties was most effectively produced by molecular bridges formed by photopolymerization. The photopolymerization leads to the "hardening" of pellets prepared by pressing of organoapatite powders. The reaction was found to be more facile in the microstructure of the organomineral, and it is potentially useful in the surgical application of organoapatites as artificial bone.

Apatites↗
PubMed1993

Organoapatites: materials for artificial bone. III. Biological testing.

This article reports on the in vivo testing of new artificial bone materials we have termed "organoapatites." These materials consist of mineral networks in which organic polymers are intimately dispersed by nucleation and growth of apatite crystals from a mother liquor containing the organic substances. Organoapatites were tested as implants in adult canine cortical bone for periods in the range from 12-35 weeks and fluorochromes were used in the model to investigate the kinetics of bone growth or repair. The analysis of histological samples was carried out using histomorphometric methods as well as fluorescence microscopy. Results showed excellent apposition of poly(amino acid) organoapatites with mineralized bone and fibrous encapsulation when a synthetic polyelectrolyte was the only organic component. This observation suggests that the molecularly dispersed organic dopant amounting to only 2-3% by weight of the microstructure can play a critical role in the tissue response to the implant. Relative to apatite controls, organoapatites were also found to have greater resistance to fragmentation in vivo and those containing amino acid units revealed interfacial bioerosion accompanied by regeneration of mineralized tissue. Design of organoapatite compositions and microstructures may therefore be useful in achieving the specific rate of biological response which is clinically desired.

Animals↗
PubMed1991

Calibration of dual-energy x-ray absorptiometry for bone density.

Bone mineral content (BMC, g) using DEXA (Lunar DPX) was measured on known hydroxyapatite samples in a water bath in the presence of uniform and nonuniform covering of fat-equivalent materials. Selective placement of paraffin over bone had a greater effect than lard in reducing apparent BMC, and polycarbonate plastic had a lesser effect. Measured BMC was 100.1 +/- 1.1% of actual hydroxyapatite weight when (1) fat over bone was about twice the mass of hydroxyapatite, and (2) the surrounding soft tissue was 15-30% fat. There was a linear relationship between observed and expected BMC, area (cm2), and bone mineral density (BMD, g/cm2) measured on an aluminum phantom using either the Lunar DPX or the Hologic QDR-1000. The measured area with the two densitometers was identical, but BMC differed. For both an anthropomorphic phantom and human subjects, use of a constant-threshold (0.2 g/cm2) edge-detection algorithm excluded less low-density bone from the transverse processes than the standard DPX edge-detection algorithm. Differences in edge detection could influence the results obtained with phantoms and in vivo and make system intercomparison difficult.

Absorptiometry, Photon↗
PubMed1991

DEXA measurement of spine density in the lateral projection. I: Methodology.

Bone mineral content and bone mineral density (BMC in g and BMD in g/cm2) were measured using dual-energy X-ray absorptiometry (DEXA). DEXA scans in the lateral decubitus position required about 12 minutes for the L2-L4 sequence at 0.75 mA (dose 5 mrem) and 4 minutes at 4.75 mA (7 mrem). The former scans were done with the Lunar DPX densitometer and the latter with the Lunar DPX-L. One test of the algorithms used for measurement is the equality of BMC in both AP and lateral projections. BMC in the lateral projection averaged about 1% lower than in the AP projection in phantoms and for L2 + L3 in 8 subjects, but the difference was not significant. Additional tests were done on the effects of tissue thickness and position from the tabletop. There was little or no influence of tissue thickness from 18 to 30 cm on BMD results, but there was a small influence of thickness below 18 cm (0.01 g/cm2; P = 0.01) and of distance from the tabletop at extremes of positioning (0.02 g/cm2; P = 0.06). The precision in vivo was similar for both 4- and 12-minute scans; the standard deviation of repeat measurements was about 0.02 g/cm2, which was about 2% relative to the mean BMD for a region within the vertebral body. The latter region included half the BMC of the body, or 24% of the entire vertebra. Results of 4-minute scans on the DPX and 12-minute scans on the DPX-L in 9 subjects were highly correlated (r = 0.98; P less than 0.001).

Absorptiometry, Photon↗