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Biomedical subjects

A R Smith

Publications and source records attributed to A R Smith.

At least 19 recordsLinked to original sources
PubMed1995

Patterns of care survey results: treatment planning for carcinoma of the prostate.

PURPOSE: Treatment planning has been defined differently at various institutions to encompass tasks ranging from the initial evaluation of the patient to the delivery of the treatment as well as a more narrow view, focused primarily on isodose computation. To evaluate the impact of much of the new treatment-planning technology that has become available, it is necessary to define and develop recommended guidelines for the treatment-planning process. METHODS AND MATERIALS: The 1989 Patterns of Care Study (PCS) included questionnaires to access treatment planning practices currently in use for the entire census of oncology facilities in the United States. These questionnaires were developed by a consensus committee consisting of both physicists and radiation oncologists whose charge was to formulate a description of current treatment-planning practices. The description was based on the committee's experience and knowledge of the treatment-planning process considered to be widely available and in general use, as well as a review of the literature. From the description of the treatment-planning process, a set of guidelines for treatment planning was developed for prostate as well as each of the other disease sites included in the PCS. Data from the study defined the general structure, methodology, process, and tools used by each institution involved in the Patterns of Care Survey Study. National averages for all of the variables were calculated with weighted averages, with the weights reflecting the sample design and number of patients in the different types of facilities. The data were stratified according to academic, hospital, or free-standing facility and were compared with the Consensus Guidelines for Treatment Planning of the Prostate. DISCUSSION: Based on the consensus statement, the treatment-planning process was separated into the following categories: (a) Treatment-Planning Workup, (b) Treatment Plan Implementation, (c) Treatment Delivery, (d) Treatment Verification, and (e) Quality Assurance. The results from the survey were summarized for each category and compared with the consensus statement. CONCLUSIONS: Although there is an increasing trend toward using computed tomography (CT) information to acquire individualized patient data, volume definition and localization are often completed in the simulator without the direct use of CT information (47%). As more sophisticated beam arrangements and blocking are used, one needs to look at the full three-dimensional (3D) volume to ensure that there are no marginal misses due to blocking and beam arrangement. Improved and more widespread use of immobilization devices is also required with conformal treatments and reduced margins. The results of the survey helped to identify and establish the standard of practice for treatment planning of the prostate as well as to provide documentation for better defining a complete description of the treatment planning process. Well-documented guidelines will provide more consistent treatment of patients, which should have an impact on outcome.

Clinical Protocols↗
PubMed1995

Treatment planning for Hodgkin's disease: a patterns of care study.

PURPOSE: To conduct a survey of the process of treatment planning for the radiation treatment of Hodgkin's Disease in the United States, and to compare survey results with consensus guidelines as determined by recognized experts. METHODS AND MATERIALS: A consensus committee developed guidelines for the radiotherapeutic management of Hodgkin's Disease. A series of survey forms were designed to evaluate the standards of practice and compare these with the consensus guidelines. A total of 61 facilities divided evenly into the strata of academic, hospital based, and free standing had eligible Hodgkin's Disease cases. There were 275 eligible cases of Hodgkin's Disease evaluated. Data collected from the radiation oncology records included treatment-specific parameters such as energy, dose, blocking, and calculations, as well as treatment planning practices. Statistical analysis was performed on each data element and for all institution strata. RESULTS: For a number of treatment parameters, there were some discrepancies note between the current United States practice and the consensus guidelines. Some significant differences were found in practice between the stratified institution types. A representative sample of results are: the majority of Hodgkin's Disease patients are treated with x-ray energies in the recommended range, between 4 and 10 MV. Standard mantle (for upper extended field treatment) and modified spade (for lower extended field treatments) are the fields of choice for all types of facilities. The consensus guidelines recommended that dose calculations at multiple points be obtained; however, 15% of patients in the survey received only a single point calculation. Current irregular field dosimetry calculation software does not take account of inhomogeneities. Thirty percent of Hodgkin's Disease patients do not receive a gap calculation for the abutment of upper and lower extended fields. In 70% of treatment fields, no compensation is used. Very few patients receive any kind of in vivo dosimetry check. CONCLUSION: The survey served to verify that, in general, Hodgkin's Disease treatment planning at all strata of institution has kept pace with recommended practice as delineated in current literature and texts. Small pockets of practice still need improvement in technique and equipment. Changes in practice were identified that can contribute to improved dose uniformity and accuracy.

Consensus Statements as Topic↗
PubMed1995

Treatment planning structure and process in the United States: a "Patterns of Care" study.

PURPOSE: To conduct a study of the structure and process of treatment planning in the United States. METHODS AND MATERIALS: A Patterns of Care treatment planning consensus committee developed a survey form that was used to gather data for 106 items relating to the structure and process of treatment planning. These questions were general in nature and not specific to any particular disease site. Seventy-three facilities were randomly selected for site visits from the 1321 radiation therapy facilities in the United States: 21 academic, 26 hospital, and 26 free-standing. During the site visit the facility physicist, assisted by the site-visit physicist, completed the form. RESULTS: Twenty-nine percent of facilities have cobalt-60 machines; 25% have 4 MV linacs; 75% have photon energies in the range of 5-8 MV; and less than 10% have energies greater than 20 MV. Academic facilities led hospital and free-standing facilities by about 30 percentage points in the availability of all electron energies (88 vs. 58%, approximately, in the range 4-13 MeV and scaling downward to about 60 vs. 30% at the highest energies). The national averages for the availability of Cs-137, Ir-192, and I-125 were 87, 73, and 44%, respectively. Computerized tomography (CT) scanning is not available or not used in 15% of hospital and free-standing facilities. Ninety-six percent of facilities have treatment planning computers; at 10% of facilities physicians do not participate in treatment planning. The estimated national averages of facilities having formal quality assurance (QA) programs for treatment planning systems, simulators, film processors, and blocking systems are 44, 79, 62, and 55%, respectively. Sixty-three percent of facilities obtain independent machine calibrations. CONCLUSION: This is the first patterns of treatment planning study carried out in the United States and the results reported here will establish a baseline for future studies. The present study has identified some elements that were unexpected, such as the percentage of facilities lacking formal QA programs for treatment planning systems; however, it has not established any impact of such findings. It is recommended that future studies include the availability of new technologies such as multileaf collimation, dynamic wedges, digital portal imaging, and CT simulation. With the increasing nationwide concern with the cost of health care, we must continue to monitor the implementation, use, and impact on treatment outcome of new and expensive technologies.

Brachytherapy↗
PubMed1995

Reagent strip testing urine for significant bacteriuria in a urodynamic clinic.

OBJECTIVES: To determine the effectiveness of two reagent strips in detecting significant bacteriuria amongst patients attending for urodynamic assessment. PATIENTS AND METHODS: Four hundred patients undergoing urodynamic assessment were recruited for the study. Routine diagnostic catheter specimens of urine were tested for nitrite, leucocytes and protein. RESULTS: The leucocytes and nitrite strips had a high specificity rate of 99.5%. The frequency of significant bacteriuria in our population was 7% (n = 28). CONCLUSION: Culturing samples which test negative for these strips is unnecessary. Reagent strip testing of urine provides a cheap, rapid method of screening for infection.

Ambulatory Care↗
PubMed1995

Gluco-oligosaccharide production by a strain of Erwinia amylovora.

When grown in sorbitol-asparagine-salts medium, cells of Erwinia amylovora isolate T83 released a mixture of oligosaccharides and lipopolysaccharide in place of extracellular polysaccharide. The oligosaccharide fraction was usually readily separable from lipopolysaccharide by gel permeation chromatography, but some samples required disaggregation by preliminary treatment with EDTA. By 1H- and 13C-NMR spectroscopy, methylation analysis and mass spectrometry, the oligosaccharide fraction was shown to consist of terminal, beta-1,2- and beta-1,2,6-linked D-glucose residues in the ratio 2.2:2.6:1, indicating a branched oligosaccharide structure. The purified oligosaccharide fraction was partially resolved by gel permeation chromatography into two components containing approximately equal amounts of glucose. When grown on pear slices, isolate T83 produced normal extracellular polysaccharide.

Erwinia↗
PubMed1995

Cellular fatty acid analysis of Bacillus thuringiensis ssp. israelensis (ONR-60A).

The cellular fatty acid composition of Bacillus thuringiensis ssp. israelensis (B.t.i.) ONR-60A was determined by gas-liquid chromatography (GLC). Isolates of ONR-60A were obtained from the Bacillus Genetic Stock Center, Pasteur Institute, and USDA culture collections. These isolates were compared to one another and the culture collections differed in the strains that they contained. Eleven separate strains of ONR-60A were identified, based on fatty acid composition of the cell envelope. The current Pasteur Institute international standard for B.t.i., IPS 82, was also analyzed and it consisted of 3 strains using these same criteria. Profiles were created for each strain found in ONR-60A and IPS 82, and validated against profiles of commercially produced B.t.i. from 2 time periods, 1983-84, and 1990-94. Approximately 84% of the commercially produced B.t.i. (134 out of 160 agar plates) was identified as belonging to the strains found in ONR-60A and in IPS 82. The most prevalent strain found in IPS 82 is also the most prevalent strain in the recently produced commercial material, 40.8% of the commercial plates analyzed, but commercially produced B.t.i. also retained a strong ONR-60A ancestry (35% of the plates analyzed).

Bacillus thuringiensis↗
PubMed1994

6-Thioguanine-induced growth arrest in 6-mercaptopurine-resistant human leukemia cells.

The thiopurines 6-thioguanine (6TG) and 6-mercaptopurine (6MP) are cytotoxic to proliferating cells by a mechanism involving incorporation into DNA via the purine salvage pathway, and resistance to these agents can be conferred by lack of the salvage pathway enzyme hypoxanthine-guanine phosphoribosyltransferase. However, human and murine hypoxanthine-guanine phosphoribosyltransferase-deficient leukemia cell lines have been shown to respond to 6TG by growth arrest and differentiation by a mechanism apparently not involving incorporation of 6TG into DNA. If so, leukemia cells resistant to 6MP should still respond to 6TG by growth arrest via an undescribed epigenetic mechanism. To test this, polyclonal 6MP-resistant variants were produced from three human leukemia cell lines, HL-60, U937, and CCRF-CEM. Treatment of both sensitive and resistant cells with 6TG induced growth arrest. The effect of 6TG in the 6MP-sensitive HL-60 and U937 cells was associated with significant loss of viability and DNA fragmentation. In contrast, the 6TG-treated 6MP-resistant cells exhibited a slower decline in viability and no DNA fragmentation. To identify the mechanism by which 6TG may induce growth arrest, tRNA was isolated from 6MP-resistant cells cultured for 48 h with 6TG. 6TG was found to be incorporated into tRNAs normally containing queuine in the anticodon wobble position. These studies may provide a basis for the development of new therapeutic regimens for the treatment of leukemia.

Apoptosis↗
PubMed1994

Application of airborne gamma spectrometric survey data to estimating terrestrial gamma-ray dose rates: an example in California.

We examined the applicability of radioelement data from the National Aerial Radiometric Reconnaissance, an element of the National Uranium Resource Evaluation, to estimate terrestrial gamma-ray absorbed dose rates, by comparing dose rates calculated from aeroradiometric surveys of uranium, thorium, and potassium concentrations with dose rates calculated from a radiogeologic data base and the distribution of lithologies in California. Gamma-ray dose rates increase generally from north to south following lithological trends, with low values of 25-30 nGy h-1 in the northernmost 1 x 2 degrees quadrangles between 41 and 42 degrees N to high values of 75-100 nGy h-1 in southeastern California. Lithologic-based estimates of mean dose rates in the quadrangles generally match those from aeroradiometric data, with statewide means of 63 and 60 nGy h-1, respectively. These are intermediate between a population-weighted global average of 51 nGy h-1 reported in 1982 by UNSCEAR and a weighted continental average of 70 nGy h-1, based on the global distribution of rock types. The concurrence of lithologically and aeroradiometrically determined dose rates in California, with its varied geology and topography encompassing settings representative of the continents, indicates that the National Aerial Radiometric Reconnaissance data are applicable to estimates of terrestrial absorbed dose rates from natural gamma emitters.

Background Radiation↗
PubMed1994

Effect on lipopolysaccharide structure of aeration during growth of a plum isolate of Pseudomonas syringae pv. morsprunorum.

The composition of lipopolysaccharide (LPS) extracted with aqueous phenol from a virulent English plum isolate of Pseudomonas syringae pv. morsprunorum varied according to the partial pressure of oxygen (pO2) in the culture medium at the time of harvest. When pO2 was low, the organism grew slowly and produced smooth LPS bearing rhamnan sidechains. As pO2 was raised, the rate of growth increased and smooth LPS was replaced by a rough species deficient in rhamnose, which co-extracted with a D-glucan. Organization of rhamnose and glucose into separate polymers was shown by the selective susceptibility of the rhamnose-containing polymer to hydrolysis by rhamnanase of the phage A7. By methylation analysis, GC-MS, and 1H- and 13C-NMR spectroscopy, the glucan was shown to consist of alpha (1-->4)-linked residues with alpha (1-->4,6)-branch points and non-reducing terminal residues in the approximate ratio 4:1:1, resembling glycogen in composition. A glucan which co-extracted with LPS using phenol/water from an avirulent plum isolate that was resistant to lysis by phages A1 and A7 was shown by methylation analysis to have a similar structure. Whether the effect on LPS composition was due directly to pO2, or was dependent on the rate of growth, has not been established. It is suggested that, because epiphytic growth would entail exposure to high pO2, English plum isolates growing on the surfaces of host plants might be unable to produce smooth LPS. Since cell surface composition affects virulence in plant-pathogenic pseudomonads, this effect could account for the observed failure of the English plum isolates to enter the host via leaf scars.

Aerobiosis↗
PubMed1994

Role of connective tissue and muscle in pelvic floor dysfunction.

This paper covers the role and anatomy of connective tissue and muscle in the normal pelvic floor of women. Current understanding of the changes in these components of pelvic floor dysfunction is discussed. Areas of ignorance in need of further research are highlighted.

Fascia↗
PubMed1993

Parental perceptions of information about medication prescribed for their children.

AIMS: The study aimed to examine parents' perceptions of the information provided to them on prescribed medication; how it might be improved and; parental level of knowledge of medication administration. METHODS: 245 parents completed a questionnaire at a preschool health day. The questionnaire covered parental opinion on whether the doctor provided enough information about illness and medication, recall of pharmacist's instructions on medication, parental general knowledge of medication and what parents wanted to know about medication for their children. RESULTS: The findings indicated there was an overall lack of information from the doctor on side effects and what to do if problems occurred with medication. Furthermore, half (49%) of the parents did not recall receiving any information from the pharmacist. Parents appeared to understand the basics of medication administration. CONCLUSIONS: It is suggested that improvements should be made regarding the information given to parents on prescribed medication. This may improve satisfaction with the service received from health professionals, such as doctors and pharmacists, and increase patient compliance with treatment regimes.

Adult↗
PubMed1993

Initiation of multi-leaf collimator conformal radiation therapy.

Clinical studies have been initiated in conformal radiotherapy using a computer controlled multi-leaf collimator. Quantitative dosimetry and treatment planning studies comparing field shaping by lead alloy blocks and the multi-leaf collimator demonstrate the clinical acceptability of the multi-leaf collimator. Sixteen patients with tumors in multiple sites have received some part of their treatments with both blocking systems. Studies of dosimetry and field shaping show that the multi-leaf collimator produces clinically acceptable blocking for most field shapes and disease sites. The 80-20% penumbra was characterized for a wide range of shaped beams. For straight edges perpendicular to the leaf travel, the penumbra of measured dose distributions from the multi-leaf collimator is equal to conventional divergent blocking. When the multi-leaf collimator leaves approach a contour at an angle, the penumbra increases. At forty-five degrees, the maximum angle of approach, the penumbra is approximately 4 mm wider than that for divergent blocks. Three-dimensional treatment planning demonstrates that equivalent dose distributions can be obtained from the two field shaping systems. The multi-leaf collimator can be used effectively and efficiently to treat a variety of disease sites. Its optimal utility may be in treating complex fields--five or more shaped coplanar or non-coplanar beams. It is well suited for conformal therapy applications.

Humans↗
PubMed1993

Characterization of a multi-leaf collimator system.

Commissioning measurements for a multi-leaf collimator installed on a dual energy accelerator with 6 and 15 MV photons are described. Detailed dosimetric characterization of the multi-leaf collimator is a requirement for modeling the collimator with treatment planning software. Measurements include a determination of the penumbra width, leaf transmission, between-leaf leakage, and localization of the leaf ends and sides. Standard radiographic film was used for the penumbra measurements, and separate experiments using radiochromic film and thermoluminescent dosimeters were performed to verify that distortions of the dose distribution at an edge due to changing energy sensitivity of silver bromide film are negligible. Films were analyzed with a scanning laser densitometer with a 210 micron spot. Little change in the penumbra edge distribution was noted for different positions of a leaf in the field. Experiments localizing the physical end of the leaves showed less than 1 mm deviation from the 50% decrement line. This small difference is attributed to the shaped end on the leaves. One side of a single leaf corresponded to the 50% decrement line, but the opposite face was aligned with a lower value. This difference is due to the tongue and groove used to decrease between-leaf leakage. For both energies, approximately 2% of photons incident on the multi-leaf collimator are transmitted and an additional 0.5% leakage occurs between the leaves. Alignment of the leaves to form a straight edge results in a penumbra profile which compares favorably with the standard technique of using alloy blocks. When the edge is stepped, the isodose lines follow the leaf pattern and the boundary is poorly defined compared to divergent blocks.

Equipment Design↗
PubMed1993

Amplification of rDNA loci to detect and type Neisseria meningitidis and other eubacteria.

In 1991-92, Neisseria meningitidis group C was isolated from the blood of eight students in Urbana, Illinois, USA, and from the cerebrospinal fluid of one student from a nearby community, Decatur, Illinois. These and other bacterial species were analysed by PCR fingerprinting using primers selected from the ribosomal (r)DNA loci. A rDNA primer pair spanning a region within the 16S rDNA amplified a predicted 280 base pair (bp) DNA fragment from Neisseria spp. and fragments of different sizes for other genera. This primer pair specifically detected a carrier of N. meningitidis in a small clinical battery. Identity of the fragment was confirmed by restriction endonuclease analysis. A 600 bp fragment was also amplified from the 16S-23S internal transcribed spacer (ITS) of N. meningitidis; amplification from six other genera yielded different-sized fragments. Digestion of the ITS fragment from N. meningitidis with Alu I revealed three patterns; pattern I was found only for serogroup C isolates, and it was the dominant pattern among recent isolates with the exception of the one from Decatur. The isolate from Decatur yielded pattern III which suggested a non-clonal relationship to the seven isolates from Urbana. Patterns II and III were more prevalent in isolates from the 1960's and 1980's. PCR-based analysis of these loci can complement the techniques which are currently used for the detection and typing of these and other eubacteria.

Adult↗
PubMed1993

Purification and preliminary characterization of permethrinase from a pyrethroid-transforming strain of Bacillus cereus.

Bacillus cereus SM3 was isolated on a mineral salts medium with Tween 80 as the primary carbon source. It was able to hydrolyze second- and third-generation pyrethroids, thereby generating noninsecticidal products. The enzyme responsible for this hydrolytic reaction was named permethrinase for this study. This is the first instance in which pyrethroid detoxification has been achieved with a cell-free microbial enzyme system. Permethrinase was purified by ion-exchange chromatography and gel filtration chromatography. The molecular mass of native permethrinase was 61 +/- 3 kDa, as estimated by Sephadex G-100 gel filtration. This novel microbial esterase seems to be a carboxylesterase. Permethrinase activity had an optimum pH of 7.5 and a temperature optimum of 37 degrees C. No cofactors or coenzymes were required for permethrinase activity. The enzyme may be a serine esterase, as it seems to be sensitive to the organophosphorus compound tetraethylpyrophosphate at concentrations in the micromolar range. Addition of dithiothreitol afforded permethrinase protection against the inhibitory effects of the sulfydryl agents p-chloromercuribenzoate and N-ethylmaleimide. The enzyme was stable over a range of temperatures. Cell extracts of strain SM3 also contained another esterase, which was active towards beta-naphthylacetate, but this enzyme was distinct from permethrinase.

Bacillus cereus↗
PubMed1993

Use of cellular fatty acid analysis to characterize commercial brands of Bacillus thuringiensis var. israelensis.

The cellular fatty acid composition of Bacillus thuringiensis var. israelensis (B.t.i.) from 5 commercial brands (Vectobac, Acrobe, Skeetal, Bactimos and Teknar), as well as of the current International Standard for B.t.i. (IPS 82), was determined using a Hewlett-Packard Microbial Identification System. The original strain of B.t.i., B.t. var. kurstaki, B.t. var. thuringiensis, B.t. var. morrisoni and Bacillus sphaericus strain 2362 were used as outgroups. Acrobe, Bactimos, Teknar, Vectobac and IPS 82 consisted of the same strain. Skeetal represented a different strain than the other commercially produced B.t.i. Our results indicate that cellular fatty acid analysis can be used to distinguish among the forms of B.t.i. produced by various manufacturers.

Bacillus thuringiensis↗