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2.
IEEE Trans Syst Man Cybern B Cybern ; 41(6): 1544-55, 2011 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-21659031

RESUMEN

Robots are frequently presented with vast arrays of diverse data. Unfortunately, perfect memory and recall provides a mixed blessing. While flawless recollection of episodic data allows increased reasoning, photographic memory can hinder a robot's ability to operate in real-time dynamic environments. Human-inspired forgetting methods may enable robotic systems to rid themselves of out-dated, irrelevant, and erroneous data. This paper presents the use of human-inspired forgetting to act as a filter, removing unnecessary, erroneous, and out-of-date information. The novel ActSimple forgetting algorithm has been developed specifically to provide effective forgetting capabilities to robotic systems. This paper presents the ActSimple algorithm and how it was optimized and tested in a WiFi signal strength estimation task. The results generated by real-world testing suggest that human-inspired forgetting is an effective means of improving the ability of mobile robots to move and operate within complex and dynamic environments.

3.
Front Pharmacol ; 12: 719268, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-34497520

RESUMEN

Diabetic cardiomyopathy (DCM) is a primary disease in diabetic patients characterized by diastolic dysfunction leading to heart failure and death. Unfortunately, even tight glycemic control has not been effective in its prevention. We have found aberrant diastolic Ca2+ concentrations ([Ca2+]d), decreased glucose transport, elevated production of reactive oxygen species (ROS), and increased calpain activity in cardiomyocytes from a murine model (db/db) of type 2 diabetes (T2D). Cardiomyocytes from these mice demonstrate significant cell injury, increased levels of tumor necrosis factor-alpha and interleukin-6 and expression of the transcription nuclear factor-κB (NF-κB). Furthermore, decreased cell viability, and reduced expression of Kir6.2, SUR1, and SUR2 subunits of the ATP-sensitive potassium (KATP) channels. Treatment of T2D mice with the citrus fruit flavonoid naringin for 4 weeks protected cardiomyocytes by reducing diastolic Ca2+ overload, improving glucose transport, lowering reactive oxygen species production, and suppressed myocardial inflammation. In addition, naringin reduced calpain activity, decreased cardiac injury, increased cell viability, and restored the protein expression of Kir6.2, SUR1, and SUR2 subunits of the KATP channels. Administration of the KATP channel inhibitor glibenclamide caused a further increase in [Ca2+]d in T2D cardiomyocytes and abolished the naringin effect on [Ca2+]d. Nicorandil, a KATP channel opener, and nitric oxide donor drug mimic the naringin effect on [Ca2+]d in T2D cardiomyocyte; however, it aggravated the hyperglycemia in T2D mice. These data add new insights into the mechanisms underlying the beneficial effects of naringin in T2D cardiomyopathy, thus suggesting a novel approach to treating this cardiovascular complication.

4.
Science ; 196(4285): 54-6, 1977 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-17733524

RESUMEN

If the amounts of wood consumed in deforestation to increase agricultural land and as firewood in underindustrialized countries are added to the amount consumed by the money economies as forest products, the estimates of the net amount of wood removed from the biosphere in this century should be revised upward. The per capita ratio of the weight of carbon from net wood burned to the weight of carbon from fossil fuel burned in this century has been at least 0.1 and may have approached 1.0.

5.
Science ; 167(3918): 555-8, 1970 Jan 30.
Artículo en Inglés | MEDLINE | ID: mdl-17781495

RESUMEN

Sample 10084,40 (fines, less than 1 millimeter) contains substantial amounts of the inert gases. Their concentrations are inversely proportional to particle size; hence the gases appear to be surface-correlated in the soil fragments. The most likely origin of the gas is solar wind or solar cosmic rays. Glass and feldspar are generally poorer in gas than lithic fragments. Ratios of elements in the sample differ significantly from solar values. Ratios of isotopes in the sample are similar to those in meteorites. Argon-40 appears to consist of a radiogenic and a surface-correlated component. An apparent potassium-argon age of 4.42(+0.24)(-0.28) billion years is calculated.

6.
Science ; 250(4984): 1135-9, 1990 Nov 23.
Artículo en Inglés | MEDLINE | ID: mdl-2251500

RESUMEN

Detailed kinetic investigations of a catalytic antibody that promotes the hydrolyses of an anilide and phenyl ester show that this catalyst uses a multistep kinetic sequence resembling that found in serine proteases to hydrolyze its substrates, although antibody was elicited to a single transition-state analog. Like the serine proteases the antibody catalyzes the hydrolysis reactions through a putative covalent intermediate, but unlike the enzymes it may use hydroxide ion to cleave the intermediates. Nevertheless, the antibody is a potent catalyst with turnover at higher pH values rivaling that of chymotrypsin. This analysis also reveals that turnover by the antibody is ultimately limited by product desorption, suggesting that improvements in catalytic efficiency may be achieved by judicious changes in the structure of the substrate, so that it is not superimposable on that of the eliciting hapten.


Asunto(s)
Anticuerpos/metabolismo , Enzimas/metabolismo , Acilación , Compuestos de Anilina/metabolismo , Catálisis , Concentración de Iones de Hidrógeno , Hidrólisis , Cinética , Nitrofenoles/metabolismo , Espectrometría de Fluorescencia , Termodinámica
7.
Science ; 210(4465): 66-8, 1980 Oct 03.
Artículo en Inglés | MEDLINE | ID: mdl-17751153

RESUMEN

The observed rate of change of the atmospheric carbon dioxide concentration at the South Pole, Fanning Island, Hawaii, and ocean weather station P correlates with an index of the southern oscillation and with El Niño occurrences. There are changes at all four stations that seem to be in response to the weak 1975 El Niño. Thus, even poorly developed El Niño events may affect the atmospheric carbon dioxide concentration.

8.
Neuron ; 29(3): 615-28, 2001 Mar.
Artículo en Inglés | MEDLINE | ID: mdl-11301022

RESUMEN

Sympathetic neuronal death induced by nerve growth factor (NGF) deprivation requires the macromolecular synthesis-dependent translocation of BAX from the cytosol to mitochondria and its subsequent integration into the mitochondrial outer membrane, followed by BAX-mediated cytochrome c (cyt c) release. The gene products triggering this process remain unknown. Here, we report that BIM, a member of the BH3-only proapoptotic subfamily of the BCL-2 protein family, is one such molecule. NGF withdrawal induced expression of BIM(EL), an integral mitochondrial membrane protein that functions upstream of (or in parallel with) the BAX/BCL-2 and caspase checkpoints. Bim deletion conferred protection against developmental and induced neuronal apoptosis in both central and peripheral populations, but only transiently, suggesting that BIM--and perhaps other BH3-only proteins--serve partially redundant functions upstream of BAX-mediated cyt c release.


Asunto(s)
Apoptosis/fisiología , Proteínas Portadoras/biosíntesis , Proteínas Quinasas JNK Activadas por Mitógenos , Proteínas de la Membrana , Neuronas/fisiología , Proteínas Proto-Oncogénicas c-bcl-2/fisiología , Empalme Alternativo , Animales , Animales Recién Nacidos , Proteínas Reguladoras de la Apoptosis , Proteína 11 Similar a Bcl2 , Proteínas Portadoras/genética , Proteínas Portadoras/fisiología , Caspasas/metabolismo , Células Cultivadas , Cicloheximida/farmacología , Grupo Citocromo c/metabolismo , Citosol/metabolismo , Dactinomicina/farmacología , Activación Enzimática/efectos de los fármacos , Inhibidores Enzimáticos/farmacología , Membranas Intracelulares/metabolismo , MAP Quinasa Quinasa 4 , Ratones , Mitocondrias/metabolismo , Mitocondrias/ultraestructura , Quinasas de Proteína Quinasa Activadas por Mitógenos/antagonistas & inhibidores , Quinasas de Proteína Quinasa Activadas por Mitógenos/fisiología , Mutagénesis , Factor de Crecimiento Nervioso/administración & dosificación , Factor de Crecimiento Nervioso/fisiología , Neuronas/ultraestructura , Fosfatidilinositol 3-Quinasas/fisiología , Inhibidores de las Quinasa Fosfoinosítidos-3 , Proteínas Proto-Oncogénicas/metabolismo , Proteínas Proto-Oncogénicas c-bcl-2/metabolismo , ARN Mensajero/análisis , Ratas , Reacción en Cadena de la Polimerasa de Transcriptasa Inversa , Proteína X Asociada a bcl-2
9.
Mol Neurobiol ; 55(11): 8680-8694, 2018 Nov.
Artículo en Inglés | MEDLINE | ID: mdl-29582400

RESUMEN

We have previously shown that inadequate dystrophin in cortical neurons in mdx mice is associated with age-dependent dyshomeostasis of resting intracellular Ca2+ ([Ca2+]i) and Na+ ([Na+]i), elevated reactive oxygen species (ROS) production, increase in neuronal damage and cognitive deficit. In this study, we assessed the potential therapeutic properties of the whole body periodic acceleration (pGz) to ameliorate the pathology observed in cortical neurons from the mdx mouse. pGz adds small pulses to the circulation, thereby increasing pulsatile shear stress to the vascular endothelium, which in turn increases production of nitric oxide (NO). We found [Ca2+]i and [Na+]i overload along with reactive oxygen species (ROS) overproduction in mdx neurons and cognitive dysfunction. mdx neurons showed increased activity of superoxide dismutase, glutathione peroxidase, malondialdehyde, and calpain as well as decreased cell viability. mdx neurons were more susceptible to hypoxia-reoxygenation injury than WT. pGz ameliorated the [Ca2+]i, and [Na+]i elevation and ROS overproduction and further increased the activities of superoxide dismutase, glutathione peroxidase and reduced the malondialdehyde and calpains. pGz diminished cell damage and elevated [Ca2+]i during hypoxia-reoxygenation and improved cognitive function in mdx mice. Moreover, pGz upregulated the expression of utrophin, dystroglycan-ß and CAPON, constitutive nitric oxide synthases, prosaposin, brain-derived neurotrophic, and glial cell line-derived neurotrophic factors. The present study demonstrated that pGz is an effective therapeutic approach to improve mdx neurons function, including cognitive functions.


Asunto(s)
Aceleración , Distrofia Muscular Animal/metabolismo , Distrofia Muscular Animal/patología , Neuronas/metabolismo , Fármacos Neuroprotectores/metabolismo , Óxido Nítrico/metabolismo , Animales , Apoptosis , Calcio/metabolismo , Hipoxia de la Célula , Corteza Cerebral/patología , Cognición , Masculino , Ratones Endogámicos C57BL , Ratones Endogámicos mdx , Neuronas/patología , Óxido Nítrico Sintasa/metabolismo , Estrés Oxidativo , Oxígeno , Sodio/metabolismo , Regulación hacia Arriba
10.
J Clin Endocrinol Metab ; 100(9): 3539-47, 2015 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-26126208

RESUMEN

CONTEXT: Serum estradiol (E2) levels are preserved in older reproductive-aged women with regular menstrual cycles despite declining ovarian function. OBJECTIVE: The objective of the study was to determine whether increased granulosa cell aromatase expression and activity account for preservation of E2 levels in older, regularly cycling women. DESIGN: The protocol included daily blood sampling and dominant follicle aspirations at an academic medical center during a natural menstrual cycle. SUBJECTS: Healthy, regularly cycling older (36-45 y; n = 13) and younger (22-34 y; n = 14) women participated in the study. MAIN OUTCOME MEASURES: Hormone levels were measured in peripheral blood and follicular fluid aspirates and granulosa cell CYP19A1 (aromatase) and FSH-R mRNA expression were determined. RESULTS: Older women had higher FSH levels than younger women during the early follicular phase with similar E2 but lower inhibin B and antimullerian hormone levels. Late follicular phase serum E2 did not differ between the two groups. Follicular fluid E2 [older (O) = 960.0 [interquartile range (IQR) 765.0-1419.0]; younger (Y) = 994.5 [647.3-1426.5] ng/mL, P = 1.0], estrone (O = 39.6 [29.5-54.1]; Y = 28.8 [22.5-42.1] ng/mL, P = 0.3), and the E2 to testosterone (T) ratio (O = 109.0 ± 41.9; Y = 83.0 ± 18.6, P = .50) were preserved in older women. Granulosa cell CYP19A1 expression was increased 3-fold in older compared with younger women (P < .001), with no difference in FSH-R expression. CONCLUSIONS: Ovarian aromatase expression increases with age in regularly cycling women. Thus, up-regulation of aromatase activity appears to compensate for the known age-related decrease in granulosa cell number in the dominant follicle to maintain ovarian estrogen production in older premenopausal women.


Asunto(s)
Envejecimiento/metabolismo , Aromatasa/metabolismo , Células de la Granulosa/metabolismo , Ciclo Menstrual/metabolismo , Ovario/metabolismo , Adulto , Estradiol/sangre , Femenino , Hormona Folículo Estimulante/sangre , Líquido Folicular/metabolismo , Humanos , Inhibinas , Hormona Luteinizante/sangre , Persona de Mediana Edad , Folículo Ovárico/metabolismo , Receptores de HFE/metabolismo , Testosterona/sangre , Regulación hacia Arriba , Adulto Joven
11.
Protein Sci ; 2(12): 2177-86, 1993 Dec.
Artículo en Inglés | MEDLINE | ID: mdl-8298463

RESUMEN

Phosphorylation of the peptide LRRASLG by the catalytic subunit of cAMP-dependent protein kinase was measured in the presence of various divalent metals to establish the role of electrophiles in the kinetic mechanism. Under conditions of low or high metal concentrations, the apparent second-order rate constant, kcat/Kpeptide, and the maximal rate constant, kcat, followed the trend Mg2+ > Co2+ > Mn2+. Competitive inhibition studies indicate that the former effect is not due to destabilization of the substrate complex, E.ATP.S. The effects of solvent viscosity on the steady-state kinetic parameters were interpreted according to a simple mechanism involving substrate binding, phosphotransfer, and product release steps and two metal chelation sites in the nucleotide pocket. Decreases in kcat and kcat/Kpeptide result mostly from attenuations in the dissociation rate constant for ADP and the association rate constant for the substrate, respectively. Decreases in the phosphoryl transfer rate constant have only negligible to moderate effects on these parameters. The low observed values for the association rate constant of the substrate indicate that the metals control the concentration of the productive binary form, Ea.ATP, and indirectly the accessibility of the active site. By comparison, Mg2+ is the best divalent metal catalyst because it uniformly lowers the transition state energies for all steps in the kinetic mechanism, permitting maximum flux of substrate to product. The data suggest that cAMP-dependent protein kinase uses metal ions to serve multiple roles in facilitating phosphotransfer and accelerating substrate association and product dissociation.


Asunto(s)
Cationes Bivalentes/farmacología , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Oligopéptidos/metabolismo , Secuencia de Aminoácidos , Sitios de Unión , Unión Competitiva , Catálisis , Cobalto/farmacología , AMP Cíclico/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/química , Proteínas Quinasas Dependientes de AMP Cíclico/efectos de los fármacos , Cinética , Magnesio/farmacología , Manganeso/farmacología , Modelos Químicos , Modelos Moleculares , Datos de Secuencia Molecular , Fosforilación/efectos de los fármacos , Viscosidad
12.
Protein Sci ; 9(9): 1818-27, 2000 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-11045627

RESUMEN

The binding of the methylanthraniloyl derivatives of ATP (mant-ATP), ADP (mant-ADP), 2'deoxyATP (mant-2'deoxyATP), and 3'deoxyATP (mant-3'deoxyATP) to the catalytic subunit of protein kinase A was studied to gain insights into the mechanism of nucleotide binding. The binding of the mant nucleotides leads to a large increase in fluorescence energy transfer at 440 nm, allowing direct measurements of nucleotide affinity. The dissociation constant of mant-ADP is identical to that for ADP, while that for mant-ATP is approximately threefold higher than that for ATP. The dissociation constant for mant-3'deoxyATP is approximately fivefold higher than that for 3'deoxyATP while derivatization of 2'deoxyATP does not affect affinity. The time-dependent binding of mant-ATP, mant-2'deoxyATP, and mant-ADP, measured using stopped-flow fluorescence spectroscopy, is best fit to three exponentials. The fast phase is ligand dependent, while the two slower phases are ligand independent. The slower phases are similar but not identical in rate, and have opposite fluorescence amplitudes. Both isomers of mant-ATP are equivalent substrates, as judged by reversed-phase chromatography, although the rate of phosphorylation is approximately 20-fold lower than the natural nucleotide. The kinetic data are consistent with a three-step binding mechanism in which initial association of the nucleotide derivatives produces a highly fluorescent complex. Either one or two conformational changes can occur after the formation of this binary species, but one of the isomerized forms must have low fluorescence compared to the initial binary complex. These data soundly attest to the structural plasticity within the kinase core that may be essential for catalysis. Overall, the mant nucleotides present a useful reporter system for gauging these conformational changes in light of the prevailing three-dimensional models for the enzyme.


Asunto(s)
Nucleótidos de Adenina/metabolismo , Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Colorantes Fluorescentes/química , Nucleótidos de Adenina/química , Fosforilación , Espectrometría de Fluorescencia
13.
Protein Sci ; 5(7): 1316-24, 1996 Jul.
Artículo en Inglés | MEDLINE | ID: mdl-8819164

RESUMEN

The active site of the cAMP-dependent protein kinase catalytic subunit harbors a cluster of acidic residues-Asp 127, Glu 170, Glu 203, Glu 230, and Asp 241-that are not conserved throughout the protein kinase family. Based on crystal structures of the catalytic subunit, these amino acids are removed from the site of phosphoryl transfer and are implicated in substrate recognition. Glu 230, the most buried of these acidic residues, was mutated to Ala (rC[E230A]) and Gln (rC[E230Q]) and overexpressed in Escherichia coli. In contrast to the mostly insoluble and destabilized rC[E230A], rC[E230Q] is largely soluble, purifies like wild-type enzyme, and displays wild-type-like thermal stability. The mutation in rC[E230Q] causes an order of magnitude decrease in the affinity for a heptapeptide substrate, Kemptide. In addition, two independent kinetic techniques were used to dissect phosphoryl transfer and product release steps in the reaction pathway. Viscosometric and pre-steady-state quench-flow analyses revealed that the phosphoryl transfer rate constant decreases by an order of magnitude, whereas the product release rate constant remains unperturbed. Electrostatic alterations in the rC[E230Q] active site were assessed using modeling techniques that provide molecular interpretations for the substrate affinity and phosphoryl transfer rate decreases observed experimentally. These observations indicate that subsite recognition elements in the catalytic subunit make electrostatic contributions that are important not only for peptide affinity, but also for catalysis. Protein kinases may, therefore, discriminate substrates by not only binding them tightly, but also by only turning over ones that complement the electrostatic character of the active site.


Asunto(s)
Proteínas Quinasas Dependientes de AMP Cíclico/metabolismo , Animales , Sitios de Unión , Catálisis , Proteínas Quinasas Dependientes de AMP Cíclico/química , Proteínas Quinasas Dependientes de AMP Cíclico/genética , Cinética , Ratones , Mutagénesis , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Electricidad Estática , Especificidad por Sustrato
14.
Protein Sci ; 3(2): 176-87, 1994 Feb.
Artículo en Inglés | MEDLINE | ID: mdl-8003955

RESUMEN

The crystal structure of ternary and binary substrate complexes of the catalytic subunit of cAMP-dependent protein kinase has been refined at 2.2 and 2.25 A resolution, respectively. The ternary complex contains ADP and a 20-residue substrate peptide, whereas the binary complex contains the phosphorylated substrate peptide. These 2 structures were refined to crystallographic R-factors of 17.5 and 18.1%, respectively. In the ternary complex, the hydroxyl oxygen OG of the serine at the P-site is 2.7 A from the OD1 atom of Asp 166. This is the first crystallographic evidence showing the direct interaction of this invariant carboxylate with a peptide substrate, and supports the predicted role of Asp 166 as a catalytic base and as an agent to position the serine -OH for nucleophilic attack. A comparison of the substrate and inhibitor ternary complexes places the hydroxyl oxygen of the serine 2.7 A from the gamma-phosphate of ATP and supports a direct in-line mechanism for phosphotransfer. In the binary complex, the phosphate on the Ser interacts directly with the epsilon N of Lys 168, another conserved residue. In the ternary complex containing ATP and the inhibitor peptide, Lys 168 interacts electrostatically with the gamma-phosphate of ATP (Zheng J, Knighton DR, Ten Eyck LF, Karlsson R, Xuong NH, Taylor SS, Sowadski JM, 1993, Biochemistry 32:2154-2161). Thus, Lys 168 remains closely associated with the phosphate in both complexes. A comparison of this binary complex structure with the recently solved structure of the ternary complex containing ATP and inhibitor peptide also reveals that the phosphate atom traverses a distance of about 1.5 A following nucleophilic attack by serine and transfer to the peptide. No major conformational changes of active site residues are seen when the substrate and product complexes are compared, although the binary complex with the phosphopeptide reveals localized changes in conformation in the region corresponding to the glycine-rich loop. The high B-factors for this loop support the conclusion that this structural motif is a highly mobile segment of the protein.


Asunto(s)
AMP Cíclico/farmacología , Proteínas Quinasas/química , Adenosina Difosfato/análisis , Adenosina Trifosfato/análisis , Secuencia de Aminoácidos , Animales , Ácido Aspártico/química , Sitios de Unión , Cristalización , Cristalografía por Rayos X , Electroquímica , Análisis de Fourier , Enlace de Hidrógeno , Lisina/química , Ratones , Modelos Moleculares , Datos de Secuencia Molecular , Estructura Molecular , Fosforilación , Proteínas Recombinantes/química
15.
Int J Radiat Oncol Biol Phys ; 36(3): 721-30, 1996 Oct 01.
Artículo en Inglés | MEDLINE | ID: mdl-8948358

RESUMEN

PURPOSE: Dose-volume histograms (DVHs) may be very useful tools for estimating probability of normal tissue complications (NTCP), but there is not yet an agreed upon method for their analysis. This study introduces a statistical method of aggregating and analyzing primary data from DVHs and associated outcomes. It explores the dose-volume relationship for NTCP of the rectum, using long-term data on rectal wall bleeding following prostatic irradiation. METHODS AND MATERIALS: Previously published data were reviewed and updated on 41 patients with Stages T3 and T4 prostatic carcinoma treated with photons followed by perineal proton boost, including dose-volume histograms (DVHs) of each patient's anterior rectal wall and data on the occurrence of postirradiation rectal bleeding (minimum FU > 4 years). Logistic regression was used to test whether some individual combination of dose and volume irradiated might best separate the DVHs into categories of high or low risk for rectal bleeding. Further analysis explored whether a group of such dose-volume combinations might be superior in predicting complication risk. These results were compared with results of the "critical volume model," a mathematical model based on assumptions of underlying radiobiological interactions. RESULTS: Ten of the 128 tested dose-volume combinations proved to be "statistically significant combinations" (SSCs) distinguishing between bleeders (14 out of 41) and nonbleeders (27 out of 41), ranging contiguously between 60 CGE (Cobalt Gray Equivalent) to 70% of the anterior rectal wall and 75 CGE to 30%. Calculated odds ratios for each SSC were not significantly different across the individual SSCs; however, analysis combining SSCs allowed segregation of DVHs into three risk groups: low, moderate, and high. Estimates of probabilities of normal tissue complications (NTCPs) based on these risk groups correlated strongly with observed data (p = 0.003) and with biomathematical model-generated NTCPs. CONCLUSIONS: There is a dose-volume relationship for rectal mucosal bleeding in the region between 60 and 75 CGE; therefore, efforts to spare rectal wall volume using improved treatment planning and delivery techniques are important. Stratifying dose-volume histograms (DVHs) into risk groups, as done in this study, represents a useful means of analyzing empirical data as a function of hetereogeneous dose distributions. Modeling efforts may extend these results to more heterogeneous treatment techniques. Such analysis of DVH data may allow practicing clinicians to better assess the risk of various treatments, fields, or doses, when caring for an individual patient.


Asunto(s)
Relación Dosis-Respuesta en la Radiación , Hemorragia Gastrointestinal/etiología , Neoplasias de la Próstata/radioterapia , Traumatismos por Radiación/complicaciones , Enfermedades del Recto/etiología , Recto/efectos de la radiación , Hemorragia Gastrointestinal/prevención & control , Humanos , Mucosa Intestinal/efectos de la radiación , Modelos Logísticos , Masculino , Traumatismos por Radiación/prevención & control , Enfermedades del Recto/prevención & control
16.
Int J Radiat Oncol Biol Phys ; 16(4): 977-81, 1989 Apr.
Artículo en Inglés | MEDLINE | ID: mdl-2703405

RESUMEN

SR 4233 (3-amino-1,2,4-benzotriazine 1,4-dioxide) is a bioreductive agent that selectively kills and radiosensitizes hypoxic mammalian cells in vitro and murine tumors in vivo. In an attempt to better understand the mechanism of action of the drug, and to determine whether a superior analog may exist, 15 benzotriazine-di-N-oxide analogs of SR 4233 have been evaluated to date for the following properties: hypoxic and aerobic toxicity toward CHO cells in vitro, drug-induced stimulation of oxygen consumption by incubation with respiration-inhibited cells, and acute LD50 evaluated in BALB/c mice. We noted several correlations between these biological properties of the drugs and some of their physicochemical characteristics. Both the hypoxic cytotoxicity and stimulation of oxygen consumption by respiration-inhibited cells were positively correlated with E1/2, the polarographic half-wave reduction potential, and a measure of electron affinity. The air-to-nitrogen differential cytotoxicity reached a maximum (corresponding to SR 4233) and then declined with increasing E1/2. The acute LD50 of each analog in mice decreased with increasing E1/2. One new compound, SR 4482, was found to be more toxic to hypoxic cells in vitro, but less toxic to mice, than SR 4233. It is similar in structure to SR 4233, but lacks any substituent in the 3-position of the triazine ring. This promising drug may represent a member of a new subseries of 1,2,4-benzotriazines with different structure-activity relationships.


Asunto(s)
Antineoplásicos/farmacología , Triazinas/farmacología , Animales , Antineoplásicos/toxicidad , Supervivencia Celular/efectos de los fármacos , Femenino , Dosificación Letal Mediana , Ratones , Ratones Endogámicos BALB C , Oxígeno/fisiología , Consumo de Oxígeno/efectos de los fármacos , Relación Estructura-Actividad , Tirapazamina , Triazinas/toxicidad
17.
Int J Radiat Oncol Biol Phys ; 58(3): 727-34, 2004 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-14967427

RESUMEN

PURPOSE: To compare treatment plans from standard photon therapy to intensity modulated X-rays (IMRT) and protons for craniospinal axis irradiation and posterior fossa boost in a patient with medulloblastoma. METHODS: Proton planning was accomplished using an in-house 3D planning system. IMRT plans were developed using the KonRad treatment planning system with 6-MV photons. RESULTS: Substantial normal-tissue dose sparing was realized with IMRT and proton treatment of the posterior fossa and spinal column. For example, the dose to 90% of the cochlea was reduced from 101.2% of the prescribed posterior fossa boost dose from conventional X-rays to 33.4% and 2.4% from IMRT and protons, respectively. Dose to 50% of the heart volume was reduced from 72.2% for conventional X-rays to 29.5% for IMRT and 0.5% for protons. Long-term toxicity with emphasis on hearing and endocrine and cardiac function should be substantially improved secondary to nontarget tissue sparing achieved with protons. CONCLUSION: The present study clearly demonstrates the advantage of conformal radiation methods for the treatment of posterior fossa and spinal column in children with medulloblastoma, when compared to conventional X-rays. Of the two conformal treatment methods evaluated, protons were found to be superior to IMRT.


Asunto(s)
Neoplasias Cerebelosas/radioterapia , Meduloblastoma/radioterapia , Radioterapia Conformacional/métodos , Preescolar , Estudios de Factibilidad , Humanos , Neoplasias Infratentoriales/radioterapia , Masculino , Fotones/uso terapéutico , Terapia de Protones , Planificación de la Radioterapia Asistida por Computador
18.
Int J Radiat Oncol Biol Phys ; 26(3): 551-7, 1993 Jun 15.
Artículo en Inglés | MEDLINE | ID: mdl-8514551

RESUMEN

PURPOSE: Dose escalation for prostate cancer by external beam irradiation is feasible by a 160 MeV perineal proton beam that reduces the volume of rectum irradiated. We correlated the total doses received to portions of the anterior rectum to study the possible relationship of the volume irradiated to the incidence of late rectal toxicity. METHODS: We have randomized 191 patients with stages T3 and T4 prostatic carcinoma to one of two treatment dose arms. These were: 1) 75.6 Cobalt-Gy-equivalent (CGE), 50.4 Gy delivered by 107-25 MV photons followed by 25.2 CGE delivered perineally by protons (Arm 1) or 2) 67.2 CGE delivered by 10-25 MV photons (Arm 2). RESULTS: With a median follow-up of 3.7 years, post-irradiation rectal bleeding (grades 1 and 2 only, none requiring surgery or hospitalization) from telangiectatic rectal mucosal vessels has occurred in 34% of 99 Arm-1 patients and 16% of 92 Arm-2 patients (p = 0.013). Dose-volume histograms (DVHs) for the anterior rectal wall, the posterior rectal wall and the total rectum in 41 patients treated on Arm 1 were calculated from the three dimensional dose distributions. Rectal bleeding has occurred in 14 or 34% of the 41 DVH-analyzed subset of Arm-1 patients. Both the fractional volume of the anterior rectum and the total dose received by fractional volumes of the anterior rectum significantly correlate with the actuarial probability of bleeding. CONCLUSIONS: Clinicians planning dose escalation to men with localized prostate cancer should approve with caution treatment plans raising more than 40% of the anterior rectum to more than 75 CGE without additional effort to protect the rectal mucosa because this late sequela data indicate that more than half of these men will otherwise have rectal bleeding.


Asunto(s)
Hemorragia Gastrointestinal/etiología , Neoplasias de la Próstata/radioterapia , Radioterapia/efectos adversos , Enfermedades del Recto/etiología , Recto/efectos de la radiación , Hemorragia Gastrointestinal/epidemiología , Humanos , Masculino , Estudios Prospectivos , Neoplasias de la Próstata/epidemiología , Dosificación Radioterapéutica , Enfermedades del Recto/epidemiología , Tasa de Supervivencia , Factores de Tiempo
19.
Int J Radiat Oncol Biol Phys ; 49(4): 1079-92, 2001 Mar 15.
Artículo en Inglés | MEDLINE | ID: mdl-11240250

RESUMEN

PURPOSE: To evaluate the incidence and pattern of hypopituitarism from hypothalamic (HT) and pituitary gland (PG) damage following high-dose conformal fractionated proton-photon beam radiotherapy (PPRT) to the base of skull (BOS) region in adults. The relationship between dose, volume, and PG function is explored. METHODS AND MATERIALS: Between May 1982 to October 1997, 107 adults with non-PG and non-HT neoplasms (predominantly chordoma and chondrosarcomas) of the BOS were treated with PPRT after subtotal resection(s). The median age was 41.2 years (range, 17-75) with 58 males and 49 females. Median prescribed target dose was 68.4 cobalt gray equivalent (CGE) (range, 55.8-79 CGE) at 1.80-1.92 CGE per fraction per day (where CGE = proton Gy x 1.1). The HT and PG were outlined on planning CT scans to allow dose-volume histograms (DVH) analysis. All patients had baseline and follow-up clinical testing of anterior and posterior pituitary function including biochemical assessment of thyroid, adrenal, and gonadal function, and prolactin secretion. RESULTS: The 10-year actuarial overall survival rate was 87%, with median endocrine follow-up time of 5.5 years, thus the majority of patients were available for long-term follow-up. Five-year actuarial rates of endocrinopathy were as follows: 72% for hyperprolactinemia, 30% for hypothyroidism, 29% for hypogonadism, and 19% for hypoadrenalism. The respective 10-year endocrinopathy rates were 84%, 63%, 36%, and 28%. No patient developed diabetes insipidus (vasopressin deficiency). Growth hormone deficiency was not routinely followed in this study. Minimum target dose (Dmin) to the PG was found to be predictive of endocrinopathy: patients receiving 50 CGE or greater at Dmin to the PG experiencing a higher incidence and severity (defined as the number of endocrinopathies occurring per patient) of endocrine dysfunction. Dmax of 70 CGE or greater to the PG and Dmax of 50 CGE or greater to the HT were also predictive of higher rates of endocrine dysfunction. CONCLUSION: Radiation-induced damage to the HT & PG occurs frequently after high-dose PPRT to the BOS and is manifested by anterior pituitary gland dysfunction. Hyperprolactinemia was detected in the majority of patients. Posterior pituitary dysfunction, represented by vasopressin activity with diabetes insipidus, was not observed in this dose range. Limiting the dose to the HT and PG when feasible should reduce the risk of developing clinical hypopituitarism.


Asunto(s)
Hipotálamo/efectos de la radiación , Hipófisis/efectos de la radiación , Radioterapia Conformacional , Neoplasias de la Base del Cráneo/radioterapia , Adolescente , Adulto , Anciano , Condrosarcoma/mortalidad , Condrosarcoma/radioterapia , Cordoma/mortalidad , Cordoma/radioterapia , Relación Dosis-Respuesta en la Radiación , Femenino , Estudios de Seguimiento , Humanos , Hiperprolactinemia/etiología , Hiperprolactinemia/mortalidad , Hipogonadismo/etiología , Hipotiroidismo/etiología , Hipotiroidismo/mortalidad , Imagen por Resonancia Magnética , Masculino , Persona de Mediana Edad , Terapia de Protones , Dosificación Radioterapéutica , Planificación de la Radioterapia Asistida por Computador , Neoplasias de la Base del Cráneo/mortalidad , Tasa de Supervivencia , Tomografía Computarizada por Rayos X
20.
Pediatrics ; 94(3): 310-7, 1994 Sep.
Artículo en Inglés | MEDLINE | ID: mdl-8065856

RESUMEN

BACKGROUND: Studies of alleged victims of child sexual abuse vary greatly in the reported frequency of physical findings based on differences in definition of abuse and of "findings." This study was designed to determine the frequency of abnormal findings in a population of children with legal confirmation of sexual abuse, using a standardized classification system for colposcopic photographic findings. METHODS: Case files and colposcopic photographs of 236 children with perpetrator conviction for sexual abuse, were reviewed. The photos were reviewed blindly by a team member other than the examiner, and specific anatomical findings were noted and classified as normal to abnormal on a scale of 1 to 5. Historical and behavioral information, as well as legal outcome was recorded, and all data entered into a dBase III program. Correlations were sought between abnormal findings and other variables. RESULTS: The mean age of the patients was 9.0 years (range 8 months to 17 years, 11 months), with 63% reporting penile-genital contact. Genital examination findings in girls were normal in 28%, nonspecific in 49%, suspicious in 9%, and abnormal in 14% of cases. Abnormal anal findings were found in only 1% of patients. Using discriminant analysis, the two factors which significantly correlated with the presence of abnormal genital findings in girls were the time since the last incident, and a history of blood being reported at the time of the molest. CONCLUSIONS: Abnormal genital findings are not common in sexually abused girls, based on a standardized classification system. More emphasis should be placed on documenting the child's description of the molestation, and educating prosecutors that, for children alleging abuse: "It's normal to be normal."


Asunto(s)
Abuso Sexual Infantil/diagnóstico , Genitales Femeninos/lesiones , Niño , Abuso Sexual Infantil/legislación & jurisprudencia , Colposcopía , Análisis Discriminante , Femenino , Genitales Femeninos/anatomía & histología , Humanos , Fotograbar , Examen Físico , Valores de Referencia
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