bluuebunny/crossref_metadata_2025 huggingface dataset:
RESPONSE OF CHLORELLA PYRENOIDOSA TO ALUMINUM AND LOW pH12
Authors: Foy C. D. , Gerloff G. C.
Published: August 2007

Chlorella pyrenoidosa, a green alga which has no measurable Ca requirement, tolerated much higher Al concentrations in solution than higher plants which require considerable Ca. This alga also gave significant positive yield responses to Al concentrations between 1.5 and 12 ppm (added at pH 4.6). The positive Al response was not attributable to V, Cr, Ni, Co, W, or Ti contaminants in the Al salt.

A strain of C. pyrenoidosa having even greater Al tolerance was isolated, by subjecting the original Strain I (Fitzgerald) culture to increasing Al stress. This strain, I‐Al, grew in stagnant cultures containing 48 ppm Al at an initial pH of 4.2. Its yield also was not significantly decreased by 48 ppm Al in aerated cultures when both inoculum and solution pH were 4.6. Under the same conditions the original Strain I organism was injured by 3 and 6 ppm Al and was killed by 12 ppm.

Algal strains which differ in Al tolerance may be useful in (1) studies on the mechanism of Al toxicity and mineral nutrition in general; and (2) in raising the pH, precipitating Al, and thereby detoxifying Al‐containing acid mine drainage water and commercial wastes.
THALASSIOSIRA ECCENTRICA (EHRENB.) CLEVE, T. SYMMETRICA SP. NOV., AND SOME RELATED CENTRIC DIATOMS1
Authors: Fryxell Greta A. , Hasle Grethe R.
Published: August 2007

Examination of original material from the Ehrenberg collection plus clonal cultures from the Gulf of Mexico and net hauls from widely separated stations in the world's oceans confirms that Coscinodiscus eccentricus is correctly placed as Thalassiosira eccentrica (Ehrenb.) Cleve. A closely related species, T. symmetrica, is described, with, the main differences being found in the value processes and distribution patterns. The former species is more abundant in inshore waters; the latter has been found in oceanic waters. Comparisons are drawn between these 2 species, T. mendiolana and Planktoniella sol.
THE RELATIONSHIP OF LIGHT, TEMPERATURE, AND CURRENT TO THE SEASONAL DISTRIBUTION OF BATRACHOSERMUM (RHODOPHYTA)12
Authors: Rider David E. , Wagner Richard H.
Published: August 2007

Observations of the 2 growth sites and the laboratory experiments performed on B. vagum and B. moniliforme indicate that B. moniliforme is better suited to higher intensity illumination than is B. vagutn. B. vagnm was found growing year‐round in a dark‐water stream protected from high intensity light by the filtering effect of the bog‐dark water. B. moniliforme was found growing in a clear water stream. Without the protection of dark water, the B. moniliforme disintegrated under the high light intensities of summer. In the laboratory, B. moniliforme retained a healthy macroscopic condition over a full range of light‐intensity treatments; above 250 ft‐c B. vagum was increasingly distintegrated.

Light intensity, however, was not the only factor regulating the growth, of Batrachospermum in the 2 growth sites. The pattern of growth of B. vagum in Sinking Creek varied with the depth of the water and, therefore, with the light intensity it received. However, it was found that where all Conditions were the same, the greatest percent cover of the algae was in the center of the stream where the current was the greatest. Thus it was found that within the limitations caused by water depth, current velocity can become limiting to the growth of B. vagum. Although the evidence for environmental factors affecting the growth of B. moniliforme in Smay's Run is less extensive, light intensity and current velocity in this site also appear to interact to control the growth pattern of the algae.
ULTRASTRUCTURE OF SPERMATIAL DEVELOPMENT IN THE PARASITIC RED ALGAE LEVRINGIELLA GARDNERI AND ERYTHROCYSTIS SACCATA12
Authors: Kugrens Paul , West John A.
Published: August 2007

Morphologically, the development of spermatia in Levringiella gardneri and Erythrocystis saccata is identical, although cytologically several differences are evident. Mature spermatia contain 1 or 2 large spermatial vesicles that contain fibrous material, several small mitochondria, some proplastids, and are surrounded by a wall, either single‐layered as in Erythrocystis or triple‐layered as in Levringiella. Spermatial vesicles are formed by aggregations of endoplasmic reticulum in Levringiella, whereas concentric membrane bodies and dictyosomes may be involved in Erythrocystis. In addition to being fibrillar, the contents of the vesicle assume a convoluted appearance in Levringiella. Several spermatia are formed per mother cell and are connected by small pit connections which rupture to allow spermatial release from the spermatangial branch.
ONTOGENY OF SEXUAL CONCEPTACLES IN A SPECIES OF BOSSIELLA (CORALLINACEAE)1
Authors: Johansen H. William
Published: August 2007

The first evidence of conceptacle formation in male and female plants of Bossiella californica ssp. Schmittii is the secretion of a cap below the epithallium. Subsequent development involves the disintegration of the upper enucleate parts of cortical cells below the center of the cap concomitant with the growth of tissue surrounding these cells. Protoplasts in the lower parts of these cortical cells recover and become initials of reproductive cells. Differentiation of each initial in female plants results in a supporting cells bearing 1 or 2, 2‐celled carpogonial filaments, and in male plants results in a basal cell bearing 2 or 3 spermatangial mother cells which bud off spermatangia. Following fertilization, supporting cells fuse and form a broad, thin fusion cell from the upper surface of which gonimoblast (carposporangial) filaments arise.
NUTRITIONAL STUDIES ON THE CHLOROMONADOPHYCEAE: VACUOLARIA VIRESCENS AND GONYOSTOMUM SEMEN12
Authors: Heywood Peter
Published: August 2007

Unialgal, nonaxenic cultures of Vacuolaria virestcens Cienkowsky were grown in soil‐water medium, in simple salt solutions with added peat and soil extract, and in synthetic medium. Doubling times in different media were determined: maximum growth rate (doubling time = 46.0 hr) was obtained in continuous light (210 ft‐c) at 24 ± I C. Gonyostomum semen (Ehrenberg) Diesing was isolated from a natural population and grown in soil‐water medium and a synthetic medium. Other techniques that have been used for culturing chloromonadophycean algae are reviewed.
OBSERVATIONS ON THE STRUCTURE OF SOME FORMS OFGOMPHONEMA PARVULUMKÜTZ. II. THE INTERNAL ORGANIZATION1
Authors: Dawson Penelope A.
Published: August 2007

The diatom speciesGomphonema parvulumKütz. was isolated, grown in culture, and the details of the internal organization studied by light and electron microscopy. The organism is usually identified from its frustular morphology, but members of the genusGomphonemacan be separated from other naviculoid forms by the H‐shaped chromatophore, whose lobes are connected on 3 sides across the center of the cell, and also from the position of the pyrenoid. This is situated, on the inner side of the chromatophore and is not embedded in the center of the chromatophore. New observations of this pennate diatom include details of the periplastidial network, of the Golgi vesicular activity, and of the storage products.
LIFE HISTORY STUDIES OF SELECTED BRITISH CERAMIUM SPECIES1
Authors: Edwards Peter
Published: August 2007

Ceramium shuttleworthianum, C. rubrum, and C. pedicellatum demonstrated a Polysiphonia type of life history without deviations in unialgal culture. The reported absence of fertile gametophytic plants of C. shuttleworthianum and C. flabelligerum from northern Scotland in the northern part of their geographical ranges is probably attributable to the inhibition of gametangial production by the environment.
COMPARATIVE STUDIES OF PYRENOID ULTRASTRUCTURE IN ALGAE OF THE MONOSTROMA COMPLEX123
Authors: Hori Terumitsu
Published: August 2007

The pyrenoid structure in 15 species of the Monostroma complex is very diverse us revealed by a study of the morphology of the pyrenoid matrix, associated starch shell, and pattern of intrapyrenoidalthylakoid bands. From these characteristics 8 types of pyrenoid structure were classified. The variation of pyrenoid structure was shown not only among the species studied, but also between the alternation of generations (M. angicava and M. nitidum). In M. fuscum var. splendens, M. groenlandicum, M. undulatum, and M. zostericola pyrenoid structure is the same throughout the life cycle. The pyrenoid matrix of M. zostericola is surrounded by a double membrane that prevents the direct connection of the pyrenoid matrix with chloroplast thylakoids. The pyrenoid also lacks a starch shell. These findings support the establishment of a new genus Kornmannia by Bliding to include M. zostericola. In addition, similarities in pyrenoid ultrastructure suggest an affinity of Capsosiphon fulvescens with M. groenlandicum.
AN ELECTRON MICROSCOPIC STUDY OF THE SPOROPHYTIC AND GAMETOPHYTIC PLANTS OF PADINA VICKERSIAE HOYT1
Authors: Fagerberg Wayne R. , Dawes Clinton J.
Published: August 2007

An electron microscopic comparison was made of the “isomorphic” sporophytic and gametophytic plants of Padina vickersiae. Light microscopic studies of the 2 generations showed few differences. This observation was also supported by studies at the ultrastructural level. However, minor differences in the gametophytic plant have been noted: (1) a well‐defined nucleolus in the nucleus of the non‐meristematic cell; (2) a general lack of osmiophilic globules in the chloroplasts; and (3) a clumping of chloroplasts in the maturing oogonium. The first and second differences are considered in terms of growth activity.
THE LIFE CYCLE OF BANGIA FUSCOPURPUREA IN CULTURE. I. EFFECTS OF TEMPERATURE AND PHOTOPERIOD ON THE MORPHOLOGY AND REPRODUCTION OF THE BANGIA PHASE12
Authors: Sommerfeld Milton R. , Nichols H. Wayne
Published: August 2007

The Bangia phase of Bangia fuscopurpurea was grown in laboratory culture in a variety of photoperiod and temperature regimes. Plants of the Bangia phase grown from 2 types of asexual spores, monospores and conchospores, exhibited growth differences under similar growing conditions. Plants derived from monospores grew more rapidly and matured earlier than those derived from carpospores. Day length and temperature were found to significantly influence growth rule, maturation, and plant size. Long day lengths resulted in more rapid growth in filament length and diameter and earlier spore formation and spore release. Maximum filament length was observed in a 12/12 hr light‐dark cycle at 15 C. Spore formation and release were delayed by decreasing day length or temperature. Temperature and photoperiod were also found to influence the type of spores produced by the Bangia phase. When grown at 22 C, the Bangia phase produced only monospores, which reproduced the Bangia phase. At 9 C, with photoperiods of 11 hr or more of light, the Bangia phase produced carpospores which gave rise to the alternating Conchocelis phase. The conditions under which sporogenesis occurred determined the spore type differentiated.
ULTRASTRUCTURAL OBSERVATIONS OF A COLACIUM PALMELLA: THE RESERVOIR, EYESPOT, AND FLAGELLA1
Authors: Willey Ruth L. , Durban Elisa M. , Bowen William R.
Published: August 2007

A recently described euglenoid of the genus Colacium inhabits the rectums of damselfly larvae during the winter as a nonflagellated, stalkless palmella stage. Contrary to previous reports, which were based on light microscope observations, ultrastructural observations establish that the reservoir and canal with its nonemergent flagella remain structurally intact in the palmella condition. The 2 non‐emergent flagella are structurally distinct. The larger flagellum, which probably gives rise to the single, emergent flagellant of the swimming euglenoid, has the typical 9 + 2 microtubular arrangement, together with a paraflagellar rod throughout most of its length. The crystalline paraflagellar body, typical of swimming euglenoids, is absent. The smaller flagellum has a 9 + 0 arrangement of the axonemal microtubules. This flagellum appears to terminate within the reservoir with a successive loss of number and arrangement of microtubules near its distal end. Hair‐like structures lining the reservoir membrane may represent preformed nontubular mastigonemes. The eyespot granules are clustered around the cytostome and do not display the compact organization or position typical of the flagellated stage or the stalked stage of Colacium.
“OBLIGATE” ALGAL EPIPHYTE: SMITHORA NAIADUM GROWS ON A SYNTHETIC SUBSTRATE1
Authors: Harlin Marilyn M.
Published: August 2007

The supposedly obligate epiphyte Smithora naiadum, normally found only on the sea grasses Phyllospadix scouleri and Zostera marina, grew on an artificial substrate under field conditions. This development shows that the alga does not appear to require a chemical factor from its normal host plant for (1) substrate selection and adhesion, (2) growth of basal cushion and young blades, or (3) maturation of thick cushions.
GLIDING MOTILITY OF OSCILLATORIA: ULTRASTRUCTURAL AND CHEMICAL CHARACTERIZATION OF THE FIBRILLAR LAYER1,2
Authors: Halfen Lawrence N.
Published: August 2007

Ultrastructural examination of platinum‐carbon replicated trichomes or wall fragments of 3 Oscilatoria species readily displayed the fibrillar components of the presumed motility system. These fibrils had a lateral organization as well as longitudinal continuity and wavelike distortions, which are consistent with the hypothesized movement mechanism. The fibrils were sensitive to proteolytic enzymes but resistant to hydrolytic agents, suggesting a protein composition. The fibrils and motility were unaffected by cytochalasin B.
ALGAL SUCCESSION ON ARTIFICIAL REEFS IN A MARINE LAGOON ENVIRONMENT IN GUAM1,2
Authors: Tsuda Roy T. , Kami Harry T.
Published: August 2007

Algal succession on artificial reefs constructed of tires has been studied over a 26‐mo period. Filamentous algae, ie, Calothrix crustacea, Feldmannia indica, and Sphacelaria tribuloides, are the primary colonizers; the fleshy brown alga, Dictyota bartayresii, appears soon after. Lobophora variegata is the only alga present which occurs seasonally. Low light penetration through the silly lagoon water and selective browsing by herbivorous fishes favor the blue‐greens Calothrix crustacea and Microcoleus lyngbyaceus to be the dominant algae in the climax community which, occurs within a 1‐year period.
SALINITY ADAPTATION BY DUNALIELLA TERTIOLECTA. I. INCREASES IN CARBONIC ANHYDRASE ACTIVITY AND EVIDENCE FOR A LIGHT‐DEPENDENT Na+/H+ EXCHANGE1,2
Authors: Latorella A. H. , Vadas R. L.
Published: August 2007

When Dunaliella tertiolecta, previously adapted to medium containing 0.5 M NaCl, is transferred to higher salinities, there is a lag in growth, suggesting an adaptation period. Since there is no significant difference in the Na+ content of cells grown between 0.5 and 3.5 M NaCl, a mechanism for Na+ extrusion or exclusion is indicated.

Increasing the salinity of cell suspensions stimulates an incorporation of H+ by the cells, suggesting an H+/Na+ exchange. Cells adapted to higher salinities have, increased carbonic anhydrase activity, suggesting that increased CO2 or HCO3− transport may be required at higher salinities.

Growth, of D. tertiolecta at salinities above 2.5 M requires continuous illumination; therefore a light‐driven H+/Na+ exchange accompanied by a HCO3− influx is proposed.
ELECTROPHORETIC AND IMMUNOLOGICAL ANALYSES OF SEVEN CHLOROSARCINACEAN ALGAE1
Authors: Thomas Dempsey L. , Groover Robert D.
Published: August 2007

Proteins from 7 species of chlorosarcinacean algae representing 4 genera were studied with starch and disc gel electrophoresis and immunology to determine biochemical relationships. Migration patterns of enzymes and serological reactions indicated that 4 species of Chlorosarcinopsis were closely related, whereas Friedmannia israeliensis, Fasciculochloris boldii, and Chlorosarcina longispinosa were more diverse. Malate dehydrogenase, glutamate dehydrogenase, nonspecific alpha esterases, and peroxidase (using pyrogallol as the hydrogen donor) were present in all 7 species. No peroxidase activity occurred with benzidine. Leucine aminopeptidase was obvious in only 2 species. A single distinct band of general protein in F. israeliensis and C. longispinosa suggested the presence of homogenous reserve protein. The 7 species exhibited serological affinity to 4 isolates of Protosiphon representing diverse morphology within the genus. The data are discussed relative to current knowledge of comparative morphology of chlorosarcinacean algae.
SULFUR AND THE TOXICITY OF THE RED ALGA CERAMIUM RUBRUM TO BACILLUS SUBTILIS1,2
Authors: Ikawa Miyoshi , Thomas Victor M. , Buckley Lawrence J. , Uebel J. John
Published: August 2007

Crystalline sulfur has been isolated from the red seaweed Ceramium rubrum and shown to be responsible for the toxicity of this alga to the growth of Bacillus subtilis. This alga was unusual in that it contained a much higher free sulfur content than other red and brown algae tested.
OBSERVATIONS ON THE SYMBIOSIS OF PERIDINIUM BALTICUM AND ITS INTRACELLULAR ALGA. I. ULTRASTRUCTURE1,2
Authors: Tomas Ronald N. , Cox Elenor R.
Published: August 2007

The ultrastructure of Peridinium balticum indicates that an eudosymbiont is present within the dinoflagellate. The structure and probable function of the organelles of both protists arc described and discussed. The origin of photosynthetic dinoflagellates from heterotrophic forms by means of a chrysophyte‐like endosymbiont is postulated.
PHYSIOLOGICAL ECOLOGY OF GELIDIELLA ACEROSA (FORSSKAL) FELDMANN ET HAMEL1
Authors: Rao P. Sreenivasa , Mehta V. B.
Published: August 2007

The effects of different concentrations of salinity, pH, and nutritional and growth‐promoting sub‐stances on the production of proliferations in Gelidiella acerosa were investigated, with a view of increasing the production rule of the alga in its aquiculture.
Poorly differentiated squamous cell carcinoma with osteoclastic giant‐cell‐like proliferation
Authors: Emanuel Patrick O. , Shim Helen , Phelps Robert G.
Published: August 2007

Although osteoclast giant‐cell‐like proliferations have been reported in a diverse range of human malignancies, to the best of our knowledge, they have never been described in cutaneous squamous cell carcinoma (SCC). Histologically, osteoclastic giant cell tumors within extraosseous malignancy resemble their bony and soft tissue counterparts, with round to spindle‐shaped cells admixed with osteoclast‐like multinucleate cells. These cells should be distinguished from sarcomatoid differentiation within a carcinoma; they have a benign morphology with a low nuclear to cytoplasmic ratio, minimal pleomorphism/mitoses and negative immunohistochemistry for cytokeratin. The authors report the rare occurrence of osteoclast‐like giant cells (OGCs) and accompanying epithelioid histiocytes lacking overtly malignant features in association with a poorly differentiated SCC occurring on sun‐damaged skin. Immunohistochemically, the area rich in OGCs was strongly positive for CD68 and completely negative for cytokeratin, whereas the poorly differentiated infiltrative area had the reverse immunophenotype and nuclear positivity for p63. The histological differential diagnosis and the origin of the proliferation are discussed in this article.
On Selecting Single-Level Formulations for Complex System Design Optimization
Authors: Allison James T. , Kokkolaras Michael , Papalambros Panos Y.
Published: August 2007

Design of complex products with several interacting subsystems or disciplinary analyses poses substantive challenges to both analysis and optimization, necessitating specialized solution techniques. A product or system may qualify as complex due to large scale or due to strong interactions. Single-level strategies for complex system optimization centralize decision-making authority, while multilevel strategies distribute the decision-making process. This article studies important differences between two popular single-level formulations: multidisciplinary feasible (MDF) and individual disciplinary feasible (IDF). Results presented aim at aiding practitioners in selecting between formulations. Specifically, while IDF incurs some computational overhead, it may find optima hidden to MDF and is more efficient computationally for strongly coupled problems; further, MDF is sensitive to variations in coupling strength, while IDF is not. Conditions that lead to failure of MDF are described. Two new reproducible design examples are introduced to illustrate these findings and to provide test problems for other investigations.
Automatic Synthesis of a Planar Linkage Mechanism With Revolute Joints by Using Spring-Connected Rigid Block Models
Authors: Kim Yoon Young , Jang Gang-Won , Park Jung Hun , Hyun Jin Sub , Nam Sang Jun
Published: August 2007

In traditional linkage design practice, a designer first decides the specific linkage type, such as a four- or six-bar linkage, and then varies the joint locations and link lengths until the designer finds the desired linkage. The objective of this research is to establish an automatic mechanism synthesis method that determines the linkage type and dimensions during the synthesis process. The synthesis process can be formulated as a minimization problem. However, the process can be extremely difficult and time-consuming unless there is a single unified linkage model that represents any linkage mechanism without complicating kinematic analysis and allows the use of an efficient gradient-based optimizer. The main contribution of this investigation is to propose a unified planar linkage model consisting of rigid blocks connected by zero-length springs having real-valued variable stiffness. Stiffness controlling variables are the design variable of the minimization problem and a general planar linkage can be simulated by the spring-connected rigid block model if the stiffness value is chosen appropriately. Though mechanisms involving only revolute joints are investigated and the solved problems are relatively simple, the notion of the block model and the synthesis formulation in real variables are expected to give a different perspective on mechanism synthesis.
On Satisfaction of the Fifth Necessary Condition of Proper Part Surface Generation in Design of Plunge Shaving Cutter for Finishing of Precision Involute Gears
Authors: Radzevich Stephen P.
Published: August 2007

In this paper, a novel modified scheme and effective computer representation for design of a plunge shaving cutter is presented. The paper aims to develop a novel design of shaving cutter for plunge shaving of precision involute gears. The study is carried out on the premise of satisfaction of the fifth necessary condition of proper part surface generation (PSG) when designing the plunge shaving cutter. In the current study, the author’s earlier developed DG/K method of surface generation is used together with the principal elements of analytical mechanics of gears. (The DG/K method is based on fundamental results obtained in differential geometry of surfaces, and on kinematics of multi-parametric motion of a rigid body in the E3 space. The interested reader may wish to go for details to the monograph: Radzevich, S.P., Fundamentals of Surface Generation, Monograph, Kiev, Rastan, 2001, 592 pp., and to: Radzevich, S.P., Sculptured Surface Machining on Multi-Axis NC Machine, Monograph, Kiev, Vishcha Schola, 1991, 192 pp.) In the particular case under consideration, the method employs (a) an analytical description of the gear tooth surface to be machined, (b) configuration of the plunge shaving cutter relative to the involute gear, (c) analytical representation of the coordinate systems transformations, and (d) the fifth condition of proper PSG that is adapted to finishing of precision involute gears. The fifth condition of proper PSG is investigated in the paper. On the premise of the obtained results of the investigation, a novel design of plunge shaving cutter for finishing of precision involute gears is proposed. The developed novel design of plunge shaving cutter can be used on shaving machines available on the market, e.g. on Gleason’s new Genesis™ 130SV computer numerical control (CNC) shaving machine.
Design of a Friction Clutch Using Dual Belleville Structures
Authors: Shen Wenming , Fang Weileun
Published: August 2007

This paper presents a simplified friction clutch design, which consists of the dual Belleville spring and the friction plates. This design exploits the preset angle on the Belleville spring to increase the friction area during operation; thus, the load on spring is reduced at a given transmitted torque. Due to the increasing of friction area, the Belleville spring can also act as a friction plate, and the components required for the clutch can be reduced. The maximum transmittable torque of the clutch is easily adjusted by varying the preload on the Belleville spring. Moreover, it is very easy to assemble the components of the present clutch. To demonstrate the present design, a prototype friction clutch with a Belleville spring has been fabricated and tested. We showed that the transmitted torque remained constant for different operating speeds.
Comparing computed tomography localization with daily ultrasound during image‐guided radiation therapy for the treatment of prostate cancer: a prospective evaluation
Authors: Feigenberg Steven J. , Paskalev Kamen , McNeeley Shawn , Horwitz Eric M. , Konski Andre , Wang Lu , Ma Charlie , Pollack Alan
Published: August 2007

In the present paper, we describe the results of a prospective trial that compared isocenter shifts produced by BAT Ultrasound (Nomos, Sewicky, PA) to those produced by a computed tomography (CT) unit in the treatment room to aid in positioning during image‐guided radiation therapy.

The trial included 15 consecutive patients with localized prostate cancer. All patients underwent CT and MR simulation immobilized supine in an Alpha Cradle and were treated with intensity‐modulated radiation therapy. BAT Ultrasound was used daily to correct for interfraction motion by obtaining shift in the x, y, and z directions. Two days per week during therapy, CT scans blinded to the ultrasound shifts were obtained and recorded.

We analyzed 218 alignments from the 15 patients and observed a high level of correlation between the CT and ultrasound isocenter shifts (correlation coefficients: 0.877 anterior–posterior, 0.842 lateral, and 0.831 superior–inferior). The systematic differences were less than 1 mm, and the random differences were approximately 2 mm. The average absolute differences, including both systemic and random differences, were less than 2 mm in all directions.

The isocenter shifts generated by using a CT unit in the treatment room correlate highly with shifts produced by the BAT Ultrasound system.

PACS numbers: 87.53, 87.59.fm, 87.63.Df
Image‐guided helical tomotherapy for localized prostate cancer: technique and initial clinical observations
Authors: Ramsey Chester R. , Scaperoth Daniel , Seibert Rebecca , Chase Daniel , Byrne Thomas , Mahan Stephen
Published: August 2007

The purpose of the present study was to implement a technique for daily computed tomography (CT)–based image‐guided radiation therapy and to report observations on treatment planning, imaging, and delivery based on the first 2 years of clinical experience.

Patients with previously untreated stage T1 – T3 biopsy‐proven adenocarcinoma of the prostate were considered eligible for treatment with daily CT‐guided helical tomotherapy. The prostate was targeted daily using megavoltage CT (MVCT) images that were fused with treatment‐planning CT images based on anatomic alignments. All patients were treated at 2 Gy per fraction to 76 – 78 Gy (mean: 76.7 Gy).

As part of this study, 33 prostate patients were planned, imaged, and treated with a total of 1266 CT‐guided fractions. The prostate, rectum, bladder, femoral heads, and pubis symphysis were visible in one or more slices for all 1266 MVCT image sets. The typical range of measured prostate displacement relative to a 3‐point external laser setup in this study was 2 – 10 mm [3.4 mm standard deviation (SD)] in the anterior–posterior direction, 2 – 8 mm (3.7 mm SD) in the lateral direction, and 1 – 6 mm (2.4 mm SD) in the superior–inferior direction. The obese patients in this study had a substantially larger lateral variation (8.2 mm SD) attributable to mobility of skin marks. The prostate, seminal vesicles, rectum, and bladder anatomy were used to position the patient relative to the desired treatment position without the use of implanted markers. Acute toxicities were within the expected range given the number of patients treated and the dose level.

PACS numbers: 87.50.Gi, 87.53.Mr, 87.53.Tf
Commissioning experience with cone‐beam computed tomography for image‐guided radiation therapy
Authors: Lehmann Joerg , Perks Julian , Semon Sheldon , Harse Rick , Purdy James A.
Published: August 2007

This paper reports on the commissioning of an Elekta cone‐beam computed tomography (CT) system at one of the first U.S. sites to install a “regular,” off‐the‐shelf Elekta Synergy (Elekta, Stockholm, Sweden) accelerator system. We present the quality assurance (QA) procedure as a guide for other users. The commissioning had six elements: (1) system safety, (2) geometric accuracy (agreement of megavoltage and kilovoltage beam isocenters), (3) image quality, (4) registration and correction accuracy, (5) dose to patient and dosimetric stability, and (6) QA procedures. The system passed the safety tests, and agreement of the isocenters was found to be within 1 mm. Using a precisely moved skull phantom, the reconstruction and alignment algorithm was found to be accurate within 1 mm and 1 degree in each dimension. Of 12 measurement points spanning a ‐cm volume in a Rando phantom (The Phantom Laboratory, Salem, NY), the average agreement in the x, y, and z coordinates was 0.10 mm, mm, and 0.22 mm [standard deviations (SDs): 0.21 mm, 0.55 mm, 0.21 mm; largest deviations: 0.6 mm, 1.0 mm, 0.5 mm] respectively. The larger deviation for the y component can be partly attributed to the CT slice thickness of 1 mm in that direction. Dose to the patient depends on the machine settings and patient geometry. To monitor dose consistency, air kerma (output) and half‐value layer (beam quality) are measured for a typical clinical setting. Air kerma was 6.3 cGy (120 kVp, 40 mA, 40 ms per frame, 360‐degree scan, S20 field of view); half value layer was 7.1 mm aluminum (120 kV, 40 mA).

We suggest performing items 1, 2, and 3 monthly, and 4 and 5 annually. In addition, we devised a daily QA procedure to verify agreement of the megavoltage and kilovoltage isocenters using a simple phantom containing three small steel balls. The frequency of all checks will be reevaluated based on data collected during about 1 year.

PACS number: 87.53.Xd
Radiation shielding for gamma stereotactic radiosurgery units
Authors: McDermott Patrick N.
Published: August 2007

Shielding calculations for gamma stereotactic radiosurgery units are complicated by the fact that the radiation is highly anisotropic. Shielding design for these devices is unique. Although manufacturers will answer questions about the data that they provide for shielding evaluation, they will not perform calculations for customers. More than 237 such units are now installed in centers worldwide. Centers installing a gamma radiosurgery unit find themselves in the position of having to either invent or reinvent a method for performing shielding design.

This paper introduces a rigorous and conservative method for barrier design for gamma stereotactic radiosurgery treatment rooms. This method should be useful to centers planning either to install a new unit or to replace an existing unit. The method described here is consistent with the principles outlined in Report No. 151 from the U.S. National Council on Radiation Protection and Measurements. In as little as 1 hour, a simple electronic spreadsheet can be set up, which will provide radiation levels on planes parallel to the barriers and 0.3 m outside the barriers.

PACS numbers: 87.53.Ly, 87.56By, 87.52Tr
Effect of skull shape approximations in Gamma Knife dose calculations
Authors: Berndt Anita , Beck James
Published: August 2007

Doses in Leksell GammaPlan (Elekta, Stockholm, Sweden) are calculated for each shot by summing the contribution from the 201 radiation beams emitted by the Gamma Knife (Elekta), weighted for attenuation in the tissue traversed. The patient's head is modeled based on 24 skull measurements, from which the depth to the calculation point is determined for each beam. The limited number of measurement points associated with this approach can result in substantial discrepancies between the skull model used for dose calculations and the actual skull contour from computed tomography or magnetic resonance data. A review of 24 patients found that differences between the actual and approximated skull shape gave treatment time errors as large as 4.1%, although in most instances, the errors were less than 1%. The conclusion was that the Leksell GammaPlan head model provides a quick and convenient approach for specifying the shape of the patient's head in all but extreme cases, where discrepancies as large as ~5% can result.

PACS number: 87.53.Ly
A survey on planar IMRT QA analysis
Authors: Nelms Benjamin E. , Simon Jeff A.
Published: August 2007

Quality assurance (QA) systems for intensity‐modulated radiation therapy (IMRT) have become standard tools in modern clinical medical physics departments. However, because formalized industry standards or recommendations from professional societies have yet to be defined, methods of IMRT QA analysis vary from institution to institution. Understanding where matters stand today is an important step toward improving the effectiveness of IMRT QA and developing standards.

We therefore conducted an IMRT QA survey. This particular survey was limited to users of an electronic two‐dimensional diode array device, but we took care to keep the questions as general and useful as possible. The online survey polled institutions (one survey per institution) on a collection of questions about methods of IMRT QA. The topics were general to the IMRT QA analysis methods common to all IMRT systems; none of the questions was vendor‐ or product‐specific.

Survey results showed that a significant proportion of responding institutions (32.8%) use the single‐gantry‐angle composite method for IMRT QA analysis instead of field‐by‐field analysis. Most institutions perform absolute dose comparisons rather than relative dose comparisons, with the 3% criterion being used most often for the percentage difference analysis, and the 3 mm criterion for distance‐to‐agreement analysis. The most prevalent standard for acceptance testing is the combined 3% and 3 mm criteria. A significant percentage of responding institutions report not yet having standard benchmarks for acceptance testing—specifically, 26.6%, 35.3%, and 67.6% had not yet established standard acceptance criteria for prostate, head and neck, and breast IMRT respectively.

This survey helps in understanding how institutions perform IMRT QA analysis today. This understanding will help to move institutions toward more standardized acceptance testing. But before standards are defined, it would be useful to connect the conventional planar QA analyses to their resulting impact on the overall plan, using clinically relevant metrics (such as estimated deviations in dose–volume histograms).

PACS numbers: 87.50.Gi, 87.52.Df, 87.52.Px, 87.53.Dq, 87.53.Tf, 87.53.Kn, 87.56.Fc
Duplicating a tandem and ovoids distribution with intensity‐modulated radiotherapy: a feasibility study
Authors: Malhotra Harish K. , Avadhani Jaiteerth S. , de Boer Steven F. , Jaggernauth Wainwright , Kuettel Michael R. , Podgorsak Matthew B.
Published: August 2007

Brachytherapy plays an important role in the definitive treatment of cervical cancers by radiotherapy. In the present study, we investigated whether sliding‐window intensity‐modulated radiation therapy (IMRT) can achieve a pear‐shaped distribution with a similar sharp dose falloff identical to that of brachytherapy. The computed tomography scans of a tandem and ovoid patient were pushed to both a high dose rate (HDR) and an IMRT treatment planning system (TPS) after the rectum, bladder, and left and right femoral heads had been outlined, ensuring identical structures in both planning systems. A conventional plan (7 Gy in 5 fractions, defined as the average dose to the left and right point A) was generated for HDR treatment. The 150%, 125%, 100%, 75%, 50%, and 25% isodose curves were drawn on each slice and then transferred to the IMRT TPS. The 100% isodose envelope from the HDR plan was the target for IMRT planning. A 7‐field IMRT plan using 6‐MV X‐ray beams was generated and compared with the HDR plan using isodose conformity to the target and 125% volume, dose– volume histograms, and integral dose. The resulting isodose distribution demonstrated good agreement between the HDR and IMRT plans in the 100% and 125% isodose range. The dose falloff in the HDR plan was much steeper than that in the IMRT plan, but it also had a substantially higher maximum dose. Integral dose for the target, rectum, and bladder were found to be 6.69 J, 1.07 J, and 1.02 J in the HDR plan; the respective values for IMRT were 3.47 J, 1.79 J, and 1.34 J. Our preliminary results indicate that the HDR dose distribution can be replicated using a standard sliding‐window IMRT dose delivery technique for points lying closer to the three‐dimensional isodose envelope surrounding point A. Differences in radiobiology and patient positioning between the two techniques merit further consideration.

PACS: 87.53.Jw
Daily quality assurance phantom for ultrasound image guided radiation therapy
Authors: Drever Laura , Hilts Michelle
Published: August 2007

A simple phantom was designed, constructed, tested, and clinically implemented for daily quality assurance (QA) of an ultrasound‐image‐guided radiation therapy (US‐IGRT) system, the Restitu Ultrasound system (Resonant Medical, Montreal, QC). The phantom consists of a high signal echogenic background gel surrounding a low signal hypoechoic egg‐shaped target. Daily QA checks involve ultrasound imaging of the phantom and segmenting of the embedded target using the automated tools available on the US‐IGRT system. This process serves to confirm system hardware and software functions and, in particular, accurate determination of the target position. Experiments were conducted to test the stability of the phantom at room temperature, its tissue‐mimicking properties, the reproducibility of target position measurements, and the usefulness of the phantom as a daily QA device. The phantom proved stable at room temperature, exhibited no evidence of bacterial or fungal invasion in 9 months, and showed limited desiccation (resulting in a monthly reduction in ultrasound‐measured volume of approximately 0.2 cm3). Furthermore, the phantom was shown to be nearly tissue‐mimicking, with speed of sound in the phantom estimated to be 0.8% higher than that assumed by the scanner calibration. The phantom performs well in a clinical setting, owing to its light weight and ease of operation. It provides reproducible measures of target position even with multiple users. At our center, the phantom is being used for daily QA of the US‐IGRT system with clinically acceptable tolerances of cm3 on target volume and mm on target position. For routine daily QA, this phantom is a good alternative to the manufacturer‐supplied calibration phantom, and we recommended that that larger phantom be reserved for less frequent, more detailed QA checks and system calibration.

PACS numbers: 87.66.Xa, 87.63.Df
First Report of the Emergence of CTX-M-Type Extended-Spectrum β-Lactamases (ESBLs) as the Predominant ESBL Isolated in a U.S. Health Care System
Authors: Lewis James S. , Herrera Monica , Wickes Brian , Patterson Jan E. , Jorgensen James H.
Published: August 2007

CTX-M-type extended-spectrum β-lactamases (ESBLs) have become increasingly common worldwide, with the notable exception of the United States, where TEM- and SHV-type ESBLs have appeared to predominate. We have noted the emergence of ESBLs in our health care system (the University Health System in San Antonio, TX), especially in
Escherichia coli
isolates, that preferentially hydrolyze cefotaxime rather than ceftazidime, suggesting the possibility of CTX-M-type enzymes. Microbiology laboratory records were reviewed to identify ESBL-producing isolates and to compare the diameters of ceftazidime disk diffusion zones of inhibition to cefotaxime zone diameters. All isolates had been initially detected and confirmed using the procedures recommended by the Clinical and Laboratory Standards Institute. A total of 94 stored ESBL-producing isolates recovered between January 2000 and June 2006 (predominately from blood and normally sterile fluids) were retrieved for further study and screened using PCR primers specific for the presence of CTX-M, TEM, and SHV ESBLs. Only small numbers of retained ESBL-producing isolates were available for study in 2000 and 2002. The percentages of available ESBL-producing organisms in the following years were found to produce CTX-M enzymes: 2000, 25%; 2001, 10%; 2002, 0%; 2003, 60%; 2004, 69%; 2005, 89%; and 2006, 70%. The most common CTX-M-type ESBL was CTX-M-15, followed by CTX-M-16, CTX-M-8, and CTX-M-14. Comparing the disk diffusion zone diameters of cefotaxime and ceftazidime was helpful with the initial recognition of CTX-M-producing
E. coli
, which had an average cefotaxime zone diameter 7 mm smaller than the ceftazidime zone. However, comparing ceftazidime and cefotaxime zones for CTX-M-producing
Klebsiella
spp. was not helpful with initial recognition. CTX-M enzymes were also identified in
Proteus mirabilis
,
Enterobacter
spp., and
Morganella morganii
. Based on pulsed-field gel electrophoresis typing of the
E. coli
isolates, the CTX-M-producing isolates did not represent the spread of a single clone in the institution or in the community. In conclusion, CTX-M-type ESBLs are now the most common ESBL type isolated from patients in our health care system and may also be present but unrecognized in other U.S. locales.
Intracellular Metabolism and Persistence of the Anti-Human Immunodeficiency Virus Activity of 2′,3′-Didehydro-3′-Deoxy-4′-Ethynylthymidine, a Novel Thymidine Analog
Authors: Paintsil Elijah , Dutschman Ginger E. , Hu Rong , Grill Susan P. , Lam Wing , Baba Masanori , Tanaka Hiromichi , Cheng Yung-Chi
Published: August 2007

The therapeutic benefits of current antiretroviral therapy are limited by the evolution of drug-resistant virus and long-term toxicity. Novel antiretroviral compounds with activity against drug-resistant viruses are needed. 2′,3′-Didehydro-3′-deoxy-4′-ethynylthymidine (4′-Ed4T), a novel thymidine analog, has potent anti-human immunodeficiency virus (HIV) activity, maintains considerable activity against multidrug-resistant HIV strains, and is less inhibitory to mitochondrial DNA synthesis in cell culture than its progenitor stavudine (D4T). We investigated the intracellular metabolism and anti-HIV activity of 4′-Ed4T. The profile of 4′-Ed4T metabolites was qualitatively similar to that for zidovudine (AZT), with the monophosphate metabolite as the major metabolite, in contrast to that for D4T, with relatively poor formation of total metabolites. The first phosphorylation step for 4′-Ed4T in cells was more efficient than that for D4T but less than that for AZT. The amount of 4′-Ed4T triphosphate (4′-Ed4TTP) was higher than that of AZTTP at 24 h in culture. There was a dose-dependent accumulation of 4′-Ed4T diphosphate and 4′-Ed4TTP on up-regulation of thymidylate kinase and 3-phosphoglycerate kinase expression in Tet-On RKO cells, respectively. The anti-HIV activity of 4′-Ed4T in cells persisted even after 48 h of drug removal from culture in comparison with AZT, D4T, and nevirapine (NVP). The order of increasing persistence of anti-HIV activity of these compounds after drug removal was 4′-Ed4T > D4T > AZT > NVP. In conclusion, with the persistence of 4′-Ed4TTP and persistent anti-HIV activity in cells, we anticipate less frequent dosing and fewer patient compliance issues than for D4T. 4′-Ed4T is a promising antiviral candidate for HIV type 1 chemotherapy.
Synergistic Efficacy of the Combination of ST-246 with CMX001 against Orthopoxviruses
Authors: Quenelle Debra C. , Prichard Mark N. , Keith Kathy A. , Hruby Dennis E. , Jordan Robert , Painter George R. , Robertson Alice , Kern Earl R.
Published: August 2007

The combination of ST-246 and hexadecyloxypropyl-cidofovir or CMX001 was evaluated for synergistic activity in vitro against vaccinia virus and cowpox virus (CV) and in vivo against CV. In cell culture the combination was highly synergistic against both viruses, and the results suggested that combined treatment with these agents might offer superior efficacy in vivo. For animal models, ST-246 was administered orally with or without CMX001 to mice lethally infected with CV. Treatments began 1, 3, or 6 days postinfection using lower dosages than previously used for single-drug treatment. ST-246 was given at 10, 3, or 1 mg/kg of body weight with or without CMX001 at 3, 1, or 0.3 mg/kg to evaluate potential synergistic interactions. Treatment beginning 6 days post-viral inoculation with ST-246 alone only increased the mean day to death at 10 or 3 mg/kg but had no effect on survival. CMX001 alone also had no effect on survival. When the combination of the two drugs was begun 6 days after viral infection using various dosages of the two, a synergistic reduction in mortality was observed. No evidence of increased toxicity was noted with the combination either in vitro or in vivo. These results indicate that combinations of ST-246 and CMX001 are synergistic both in vitro and in vivo and suggest that combination therapy using ST-246 and CMX001 for treatment of orthopoxvirus disease in humans or animals may provide an additional benefit over the use of the two drugs by themselves.
Effects of DNA- and
Mycobacterium bovis
BCG-Based Delivery of the Flt3 Ligand on Protective Immunity to
Mycobacterium tuberculosis
Authors: Triccas James A. , Shklovskaya Elena , Spratt Joanne , Ryan Anthony A. , Palendira Umaimainthan , Fazekas de StGroth Barbara , Britton Warwick J.
Published: August 2007

The control of intracellular pathogens such as
Mycobacterium tuberculosis
is dependent on the activation and maintenance of pathogen-reactive T cells. Dendritic cells (DCs) are the major antigen-presenting cells initiating antimycobacterial T-cell responses in vivo. To investigate if immunization strategies that aim to optimize DC function can improve protective immunity against virulent mycobacterial infection, we exploited the ability of the hematopoietic growth factor Fms-like tyrosine kinase 3 ligand (Flt3L) to expand the number of DCs in vivo. A DNA fusion of the genes encoding murine Flt3L and
M. tuberculosis
antigen 85B stimulated enhanced gamma interferon (IFN-γ) release by T cells and provided better protection against virulent
M. tuberculosis
than DNA encoding the single components. Vaccination of mice with a recombinant
Mycobacterium bovis
BCG strain secreting Flt3L (BCG:Flt3L) led to early expansion of DCs compared to immunization with BCG alone, and this effect was associated with increased stimulation of BCG-reactive IFN-γ-secreting T cells. BCG and BCG:Flt3L provided similar protective efficacies against low-dose aerosol
M. tuberculosis
; however, immunization of immunodeficient mice revealed that BCG:Flt3L was markedly less virulent than conventional BCG. These results demonstrate the potential of in vivo targeting of DCs to improve antimycobacterial vaccine efficacy.