Poster - Thurs Eve-09: Evaluation of a commercial 2D ion-chamber array for intensity modulated radiation therapy dose measurements

Experimental verification of calculated dose from a treatment planning system is often essential for quality assurance (QA) of intensity modulated radiation therapy (IMRT). Film dosimetry and single ion chamber measurements are commonly used for IMRT QA. Film dosimetry has very good spatial resolution, but is labor intensive and absolute dose is not reliable. Ion chamber measurements are still required for absolute dose after measurements using films. Dosimeters based on 2D detector arrays that can measure 2D dose in real-time are gaining wider use. These devices provide a much easier and reliable tool for IMRT QA. We report the evaluation of a commercial 2D ion chamber array, including its basic performance characteristics, such as linearity, reproducibility and uniformity of relative ion chamber sensitivities, and comparisons between measured 2D dose and calculated dose with a commercial treatment planning system. Our analysis shows this matrix has excellent linearity and reproducibility, but relative sensitivities are tilted such that the +Y region is over sensitive, while the -Y region is under sensitive. Despite this behavior, our results show good agreement between measured 2D dose profiles and Eclipse planned data for IMRT test plans and a few verification plans for clinical breast field-in-field plans. The gamma values (3% or 3 mm distance-to-agreement) are all less than 1 except for one or two pixels at the field edge This device provides a fast and reliable stand-alone dosimeter for IMRT QA.

Electronic portal imaging based on Cerenkov radiation: A new approach and its feasibility

Most electronic portal imaging devices (EPIDs) developed so far use a Cu plate/phosphor screen to absorb x rays and convert their energies into light, and the light image is then read out. The main problem with this approach is that the Cu plate/phosphor screen must be thin (approximately 2 mm thick) in order to obtain a high spatial resolution, resulting in a low x-ray absorption or low quantum efficiency for megavoltage x rays (typically 2-4%). In addition, the phosphor screen contains high atomic number (high-Z) materials, resulting in an over-response of the detector to low-energy x rays in dosimetric verification. In this paper, we propose a new approach that uses Cerenkov radiation to convert x-ray energy absorbed by the detector into light for portal imaging applications. With our approach, a thick (approximately 10-30 cm) energy conversion layer made of a low-Z dielectric medium, such as a large-area, thick fiber-optic taper consisting of a matrix of optical fibers aligned with the incident x rays, is used to replace the thin Cu plate/phosphor screen. The feasibility of this approach has been investigated using a single optical fiber embedded in a solid material. The spatial resolution expressed by the modulation transfer function (MTF) and the sensitivity of the detector at low doses (approximately one Linac pulse) have been measured. It is predicted that, using this approach, a detective quantum efficiency of an order of magnitude higher at zero frequency can be obtained while maintaining a reasonable MTF, as compared to current EPIDs.

Development of high quantum efficiency, flat panel, thick detectors for megavoltage x-ray imaging: An experimental study of a single-pixel prototype

Our overall goal is to develop a new generation of electronic portal imaging devices (EPIDs) with a quantum efficiency (QE) more than an order of magnitude higher and a spatial resolution equivalent to that of EPIDs currently used for portal imaging. A novel design of such a high QE flat-panel based EPID was introduced recently and its feasibility was investigated theoretically [see Pang and Rowlands, Med. Phys. 31, 3004 (2004)]. In this work, we constructed a prototype single-pixel detector based on the novel design. Some fundamental imaging properties including the QE, spatial resolution, and sensitivity of the prototype detector were measured with a 6 MV beam. It has been shown that the experimental results agree well with theoretical predictions and further development based on the novel design including the construction of a prototype area detector is warranted.

[Effects of pyracantha fortuneana extract on blood coagulation]

OBJECTIVE

To study the effect of the Pyracantha fortuneana extract and its defferent polar fractions on blood coagulation.

METHODS AND RESULTS

The Pyracantha fortuneana extract could noticeably shorten the coagulation time of glass slide in mice (P < 0.05) after oral administration, and also shorten the recalcification time and prothrombin time in vitro (P < 0.01, P < 0.05), while in three polar fractions of the extract, the effects of the chloroform phase that could shorten the coagulation time of glass slide in mice(P < 0.01) after oral administration, and also shorten the recalcification time and prothrombin time in vitro (P < 0.01) are more noticeable than that of the acetic ether phase (P < 0.01, P < 0.05). The petroleum ether phase has no above-mentioned effect (P > 0.05).

CONCLUSION

The Pyracantha fortuneana extract can reduce the blood coagulation. Both the chloroform phase and the acetic ether phase of the extract have activity of blood coagulation, but the petroleum ether phase does not.

[The role of AT1 receptor and cyclin kinase inhibitor p27 protein in angiotensin II-induced hypertrophy of mesangial cell]

OBJECTIVE

To investigate the role of p27 and AT1 receptor in the hypertrophy of mesangial cell (MC) induced by angiotensin II (Ang II).

METHODS

p27 protein of MC lysate was detected with Western blotting analysis. The degree of cultured MC hypertrophy was estimated through [3H] thymidine incorporation and [3H] leucine incorporation. The effect of reducing p27 expression on cell hypertrophy was analysed with p27 antisense oligodeoxynucleotide (ODN) phosphorothioate. The extracellular matrix (ECM) protein (type IV collagen and fibronectin) of MC lysate was examined with ELISA.

RESULTS

Ang II stimulated p27 expression of MC cultured in normal glucose DMEM. MC stimulated by Ang II revealed hypertrophy as well as increased [3H] leucine incorporation, decreased [3H] thymidine incorporation and increased ECM. p27 antisense ODN transfection abolished the effect of Ang II mentioned above. Losartan lowered p27 level of MC stimulated by Ang II and attenuated MC hypertrophy induced by Ang II; meanwhile [3H] leucine incorporation and ECM level decreased, [3H] thymidine incorporation increased. The effect of Losartan was dose-dependent.

CONCLUSION

Ang II induced MC hypertrophy by increasing p27 protein level through AT1 receptor. Because the cell cycle is controlled by the interplay between the positive and negative cell cycle regulatory proteins (CCRP), further research is needed to study the expression of the positive and negative CCRP in MC in order to understand better the role of CCRP in MC hypertrophy induced by Ang II.

[The achievement of industrialized healthy aquatic breeding of hippocampus and its application prospects]

The artificial industrialized aquatic breeding of Hippocampus, which is a kind of Chinese medicinal marine material, has been achieved in the artificial aquatic breeding base of Hippocampus of Guangdong Richvast Group Company since 1983. This article reported part of the achievements of the large-scale artificial aquatic breeding experiments. The prospects for the research and application of Hippocampus as health foods and drugs were also analyzed.

Enhancement of Taxol production and excretion in Taxus chinensis cell culture by fungal elicitation and medium renewal

An endophytic fungus, Aspergillus niger, isolated from the inner bark of a Taxus chinensis tree, was used as an elicitor to stimulate the Taxol (paclitaxel) production in a Taxus chinensis cell suspension culture. Different elicitor doses and elicitation times were tested in a batch culture; and the highest volumetric Taxol yield was achieved when 40 mg of the fungal elicitor (carbohydrate equivalent) l(-1) was added to the culture during the late exponential-growth phase. The elicitation resulted in a more than two-fold increase in the Taxol yield and about a six-fold increase in total secretion. The Taxol yield was further improved substantially by applying medium renewal and re-elicitation to the culture. In particular, with repeated medium renewal (in a way similar to medium perfusion) and a second elicitation of the culture, the volumetric Taxol yield was increased to 67.1+/-7.5 mg l(-1), which was about seven times the amount obtained in the non-elicited batch culture. The Taxol productivity of the perfusion-like culture with repeated fungal elicitation was 1.5 mg l(-1) day(-1), which was about 40% higher than that of the elicitor-treated batch culture and three times the productivity of the non-elicited batch culture.

Stimulation of taxol production and excretion in Taxus spp cell cultures by rare earth chemical lanthanum

The trivalent ion of a rare earth element, lanthanum, was tested for elicitor-like effects on taxol production in suspension cultures of four different Taxus spp cells. In T. yunnanensis cell cultures, the lanthanum ion at concentrations from 1.15 to 23.0 microM stimulated taxol production. The lanthanum ion also promoted taxol excretion by the T. yunnanensis cells considerably. The maximum stimulation of taxol production was achieved by the addition of 5.8 microM La3+ to the culture during mid-log growth phase, increasing the volumetric taxol yield by nearly threefold, from 2.61+/-0.37 to 9.89+/-1.92 mg l(-1) over a 28 day culture period. At higher concentrations, i.e. 23.1 and 46.2 microM, however, the lanthanum ion caused significant growth inhibition. For the other three Taxus cell lines, namely an embryo and a leave cell of T. chinensis and a stem cell of T. chinensis marv, the addition of lanthanum ion to the culture only had a significant effect on taxol production by the T. chinensis marv stem cells, increasing the volumetric yield by about threefold to 4.69+/-0.76 mg l(-1). These results suggest that lanthanum has elicitor-like effects on secondary metabolite synthesis of plant cell cultures.

Enhanced taxol production and release in Taxus chinensis cell suspension cultures with selected organic solvents and sucrose feeding

Suspension culture of Taxus chinensis cells was carried out in aqueous-organic two-phase systems for the production and in situ solvent extraction of taxol (paclitaxel). Three organic solvents, hexadecane, decanol, and dibutylphthalate, were tested at 5-20% (v/v) in the culture liquid. All of these solvents stimulated taxol release and the yield per cell, though decanol and higher concentrations of the other two solvents depressed biomass growth significantly. Ten percent dibutylphthalate was the optimal solvent for improving taxol production and release with minimal cell growth inhibition. The time of solvent addition to the culture also affected taxol production, with the addition during the late-log growth phase being most favorable. By feeding sucrose to the culture near the stationary growth phase, the cell growth and taxol production period was extended from 27 to 42 days. The combining of the two-phase culture and sucrose feeding increased the taxol yield by about 6-fold compared with the single-phase batch culture, to 36.0 +/- 3.5 mg/L, with up to 63% taxol released. This study shows that in situ solvent extraction combined with nutrient feeding is an effective process strategy for production and recovery of secondary metabolites in plant cell suspension culture.

Microtubule-associated protein 1 subunit expression in primary cultures of rat brain

Microtubule-associated protein 1A (MAP1A) and MAP1B are developmentally regulated proteins linked to axon formation. They each consist of a unique heavy chain and three common light chains. We used immunofluorescence microscopy to qualitatively assess the variability in MAP1 subunit expression between individual cells. The ratio of light chain 1 to MAP1 heavy chain varies greatly between cells with some cells expressing MAP1A heavy chain in the apparent absence of light chain 1. The results imply the existence of MAP1 molecules that differ in light chain composition. Transfection experiments indicate that the light chains differ in microtubule binding activity and subcellular targeting activity. This further suggests that the regulation of MAP1 light chain content can control MAP1 function.

Regulation of microtubule-associated protein 1B (MAP1B) subunit composition

The MAP1B and MAP1A genes each produce an mRNA that encodes a polyprotein. When cleaved, each polyprotein yields a single heavy chain and a single light chain, which become noncovalently associated. In previous work, it was found that the MAP1B light chains and heavy chains exist in a 2:1 ratio. Through use of quantitative immunoblot techniques, this finding was further examined in the developing rat brain. MAP1B heavy chain (HC) and light chain (LC1), as well as the light chain of MAP1A (LC2), were prepared in purified form for use as standards and/or immunogens for generation of antibodies for immunoblotting. Brain homogenates and microtubule-enriched fractions from developing rats were assayed for MAP1B HC and LC1 content. Results indicated that postnatal rat brain homogenates contain LC1 in a 6:1 to 8:1 molar ratio to the MAP1B HC. Purified microtubules also contain LC1 in excess of MAP1B HC, but at a ratio of 2:1. We propose that most of the excess LC1 in homogenates is either insoluble or not bound to microtubules. The findings raise the possibility of a function for the "excess" LC1 that does not require association with MAP1 HC and/or microtubules. Given a synthetic mechanism that produces MAP1B HC and LC1 in a 1:1 ratio at both transcription and translation steps, we propose that the "excess" LC1 in brain homogenates is a consequence of LC1 having a greater half-life than the MAP1B HC. Consistently with this hypothesis, a major pool of MAP1B HC is rapidly degraded after blocking protein synthesis with cycloheximide, whereas LC1 levels remain constant even after 24 hr of cycloheximide treatment.

[Stable carbon isotope characteristics of some woody plants in warm temperate zone]

It was found that the delta 13C values of the foliar, trunk, flower, and fruit of some woody plants in broad-leaved forest in warm temperate zone were affected by many factors, and showed a great interspecific difference and temporal and spatial heterogeneity. The intraspecific variation of delta 13C values was also great, with the order of Vitex negundo var. heterophylla 6.549@1000(-22.226@1000(-)-28.775@1000), Fraxinus rhynchophylla 5.706@1000(-23.687@1000(-)-29.393@1000), Jugans mandshurica 5.229@1000 (-26.146@1000-31.375@1000), Quercus liaotungensis 3.333@1000 (-24.324@1000(-)-27.657@1000), Syringa pekinensis 2.414@1000(-25.655@1000(-)-28.070@1000), and Prunus armeniaca var. ansu 2.296@1000 (-23.436@1000(-)-26.432@1000). Different organs of the same species had different delta 13C values: trunk and root barks had the low, while xylem had the highest delta 13C value. According to the relationship analysis between delta 13C value of Prunus armeniaca var. ansu xylem and environment factors, it was found that delta 13C value was strongly affected by annual mean temperature and followed by annual precipitation, mean temperature and precipitation in growth season.

Immunolocalization of dystrobrevin in the astrocytic endfeet and endothelial cells in the rat cerebellum

Dystrobrevin is a newly discovered dystrophin-associated protein that is classified as alpha- and beta-dystrobrevin. Previous studies reported that dystrophin, utrophin, syntrophin and beta-dystroglycan were expressed in the cerebellum. In the present study, we examined cellular and subcellular localization of dystrobrevin in the adult rat cerebellum immunohistochemically. Confocal microscopy showed that dystrobrevin was expressed around blood vessels and under the pia mater as dystrophin, utrophin and beta-dystroglycan were. Immunoelectron microscopy demonstrated that dystrobrevin was localized not only in the astrocytic endfeet around blood vessels and under the pia mater, but also in endothelial cells. Considering the fact that dystrobrevin possesses multiple phosphotyrosine kinase residues, these data suggest that dystrobrevin plays a role in blood-brain barrier functions as a component of the dystrophin complex.

[Improving memory effects of eel oil capsule on memory obstruction of mice hurt by anisodine]

The effects of eel oil capsule on memory obstruction of mice were observed in step-down test, step-through test, Y-maze test and Japanese labyrinth test. The results indicated that the eel oil capsule treating group with dosages of 0.234, 0.702 and 2.106 g/kg markedly enhance the acquirement, strengthing and reappearance of memory, having the functions of improving brain memory hurt by Anisodine.

Developmental expression of the protein kinase C substrate/binding protein (clone 72/SSeCKS) in rat testis identification as a scaffolding protein containing an A-kinase-anchoring domain which is expressed during late-stage spermatogenesis

The coordinated interaction of kinases, phosphatases and other regulatory molecules with scaffolding proteins is emerging as a major theme in intracellular signaling networks. In this report we show that a cDNA isolated from a rat testis expression library by interactive cloning using the regulatory subunit (R) of a type-II protein kinase A (PKA) is identical with a previously characterized protein kinase C (PKC)-binding protein termed either clone 72 [Chapline, C., Mousseau, B., Ramsay, K., Duddy, S., Li, Y., Kiley, S. C. & Jaken, S. (1996) J. Biol. Chem. 271, 6417-6422] or SSeCKS [Lin, X., Tombler, E., B., Nelson, P.J., Ross, M. & Gelman, I.H. (1996) J. Biol. Chem. 271, 28430-28438]. Deletion mutagenesis demonstrated that amino acids 1495-1524 of clone 72/SSeCKS had the ability to interact with RII. Antibodies prepared against the recombinant protein recognized a 280/290-kDa doublet and a 240-kDa protein on Western blots of rat testis cytosolic and Triton X-100 extracts. Expression of clone 72/SSeCKS mRNA and protein levels was developmentally regulated in rat testis. Northern-blot analysis showed a dramatic increase in clone 72/SSeCKS-hybridizing mRNA starting 30 days after birth. Immunohistochemical examination showed high expression levels in elongating spermatids. Clone 72/SSeCKS was not detected in mature sperm. These studies suggest a role for clone 72/SSeCKS, a PKA/PKC scaffolding protein, during the process of spermiogenesis.

Peripheral target regulation of the development and survival of spinal sensory and motor neurons in the chick embryo

Unilateral limb-bud removal (LBR) before the outgrowth of sensory or motor neurons to the leg of chick embryos was used to examine the role of limb (target)-derived signals in the development and survival of lumbar motoneurons and sensory neurons in the dorsal root ganglia (DRG). After LBR, motor and sensory neurons underwent normal initial histological differentiation, and cell growth in both populations was unaffected. Before their death, target-deprived motoneurons also expressed a cell-specific marker, the homeodomain protein islet-1. Proliferation of sensory and motor precursor cells was also unaffected by LBR, and the migration of neural crest cells to the DRG and of motoneurons into the ventral horn occurred normally. During the normal period of programmed cell death (PCD), increased numbers of both sensory and motor neurons degenerated after LBR. However, whereas motoneuron loss increased by 40-50% (90% total), only approximately 25% more sensory neurons degenerated after LBR. A significant number of the surviving sensory neurons projected to aberrant targets in the tail after LBR, and many of these were lost after ablation of both the limb and tail. Treatment with neurotrophic factors (or muscle extract) rescued sensory and motor neurons from cell death after LBR without affecting precursor proliferation of either population. Activity blockade with curare failed to rescue motoneurons after LBR, and combined treatment with curare plus muscle extract was no more effective than muscle extract alone. Treatment with the antioxidant N-acetylcysteine rescued motoneurons from normal cell death but not after LBR. Two specific inhibitors of the interleukin beta1 converting enzyme (ICE) family of cysteine proteases also failed to prevent motoneuron death after LBR. Taken together these data provide definitive evidence that the loss of spinal neurons after LBR cannot be attributed to altered proliferation, migration, or differentiation. Rather, in the absence of limb-derived trophic signals, the affected neurons fail to survive and undergo PCD. Although normal cell death and cell death after target deprivation share many features in common, the intracellular pathways of cell death in the two may be distinct.

Cloning and characterization of a testis-specific, developmentally regulated A-kinase-anchoring protein (TAKAP-80) present on the fibrous sheath of rat sperm

cAMP is important for the initiation of mammalian sperm motility. Previously we established that a type II cAMP-dependent protein kinase is tightly associated with the fibrous sheath of rat sperm. This unique cytoskeletal structure surrounds the 9+2 axonemal network in the principal piece of the flagellum. Association of the kinase to the fibrous sheath is mediated via its regulatory subunit, RII. An RII-binding overlay procedure was used to document that RII could specifically associate with fibrous sheath polypeptides of 120 and 80 kDa. In this study, we report the cloning of a rat testis-specific, developmentally regulated, RII-binding protein (TAKAP-80). A 1.2-kb cDNA clone, isolated by screening a rat testis expression library with 32P-labeled RII, hybridized to a 1.8-kb mRNA transcript present exclusively in testis. This transcript appeared at detectable levels at 30 days after birth. Over the next 10 days the mRNA levels increased greatly. This time interval corresponds to the initiation of spermiogenesis. The complete nucleotide sequence of TAKAP-80 cDNA was obtained by polymerase chain reaction and contained a continuous open reading frame of 502 amino acids. The deduced amino acid sequence showed a clear demarcation of charged and hydrophobic amino acid residues. Amino acids 1-147 of the protein contained 45% charged residues, with lysine and arginine predominating. Similarly, amino acids 268-502 also contained a high percentage of charged amino acids (35%). In contrast, amino acids 148-267 were mostly hydrophobic and contained clusters of a repeating PXXP motif where X was predominantly valine and alanine or sometimes proline. The 1.2-kb cDNA clone was inserted into the pRSET vector and expressed as a His6 tag fusion protein in Escherichia coli. The recombinant protein was soluble and bound RIIalpha, RIIbeta and type IIalpha holoenzyme by the RII-binding overlay procedure. Deletion analysis revealed that the high-affinity interaction site for RII was contained within amino acids 258-378 of TAKAP-80. Antibodies prepared against the fusion protein recognized an 80-kDa protein present in the urea-insoluble particulate fraction of rat testis and in purified fibrous sheath preparations isolated from rat epididymal sperm. Levels of the 80-kDa immunoreactive protein were significantly higher in mature (60 days old) compared with immature (30 days old) rat testis, correlating with the mRNA levels.

[Prostacyclin participates in regulation of hypoxic and high CO2 cerebrovascular tension]

By using prostacyclin synthetase inhibitor-indomethacin, the effects of prostacyclin in the presence of endothelial cell on hypoxia- and high CO2-induced vasodilatation were studied in newborn calf basilar artery strips. The results showed that indomethacin had no effects on cerebrovascular tension, but attenuated the hypoxia- and high CO2-induced vasodilatation. After destroying the endothelial cell, the cerebral vascular dilatation was decreased, and indomethacin had no obvious effect on the vascular tension. These results suggest that both prostacyclin and endothelial cell are involved in hypoxia- and high CO2-induced vasodilatation and the former is derived from endothelial cell.

Effects of a decision support system on the diagnostic accuracy of users: a preliminary report

OBJECTIVES

To assess the effects of incomplete data upon the output of a computerized diagnostic decision support system (DSS), to assess the effects of using the system upon the diagnostic opinions of users, and to explore if these effects vary as a function of clinical experience.

DESIGN

Experimental pilot study. Four clusters of nine cases each were constructed and equated for case difficulty. Definitive findings were omitted from the case abstracts. Subjects were randomly assigned to one of four clusters and were trained on the DSS prior to use.

SUBJECTS

The study involved 16 physicians at three levels of clinical experience (six general internists, four residents in internal medicine, and six fourth-year medical students), from three academic medical centers.

PROCEDURE

Each subject worked up nine cases, first without and then with ILIAD consultation. They were asked to offer up to six potential diagnoses and to list up to three steps that should be the next items in the diagnostic workup. Effects of DSS consultation were measured by changes in the position of the correct diagnosis in the lists of differential diagnoses, pre- and post-consultation.

RESULTS

The DSS lists of diagnostic possibilities contained the correct diagnosis in 38% of cases, about midway between the levels of accuracy of residents and attending general internists. In over 70% of cases, the DSS output had no effect on the position of the correct diagnosis in the subjects' lists. The system's diagnostic accuracy was unaffected by the clinical experience of the users.

Association of the regulatory subunit of a type II cAMP-dependent protein kinase and its binding proteins with the fibrous sheath of rat sperm flagellum

Demembranated rat sperm flagellar polypeptides capable of binding the regulatory subunit (RII) of a type II cAMP-dependent protein kinase, having apparent subunit molecular masses of 120, 80 and 57 kDa were identified by an RII overlay procedure [Horowitz, J. A., Wasco, W., Leiser, M. & Orr, G. A. (1988) J. Biol. Chem. 263, 2098-2104]. In this study it is shown that all three polypeptides capable of binding RII on a solid-phase blot are tightly associated with the fibrous sheath. Purified fibrous sheath preparations were capable of binding (a) [3H]cAMP and (b) purified catalytic subunits of cAMP-dependent protein kinase forming a functional holoenzyme. The 57-kDa protein was identified as RII by photoaffinity labeling with 8-azido[32P]cAMP. This peptide was phosphorylated by the catalytic subunit of cAMP-dependent protein kinase. RII alpha was also shown to form tight, specific complexes with the fibrous sheath demonstrating the presence of functional RII alpha-binding sites. Truncated RII beta fusion proteins were used to identify the N-terminal amino acids at positions 1-50 as a primary determinant for RII-binding protein interaction. Differential extraction of adult testis with buffers containing Triton X-100, urea and sodium dodecyl sulfate revealed the presence of 80-kDa (major) and 120-kDa (minor) RII-binding proteins in particulate extracts. The 80-kDa polypeptide is only expressed at late stages of spermatogenesis, i.e. during spermiogenesis, suggesting a developmental role for RII anchoring to the sperm flagellar fibrous sheath.