SEARCH · PubMed Health

Results for “depth adaptation”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 469 records · Page 26Linked to original sources

PubMed2007

Variations in lithium target thickness and proton energy stability for the near-threshold 7Li(p,n)7Be accelerator-based BNCT.

The usable range of thickness for the solid lithium target in the accelerator-based neutron production for BNCT via the near-threshold (7)Li(p,n)(7)Be reaction was investigated. While the feasibility of using a (7)Li-target with thickness equal to that which is required to slow down a mono-energetic 1.900 MeV incident proton to the 1.881 MeV threshold of the (7)Li(p,n)(7)Be reaction (i.e., t(min) = 2.33 microm) has already been demonstrated, dosimetric properties of neutron fields from targets greater than t(min) were assessed as thicker targets would last longer and offer more stable neutron production. Additionally, the characteristics of neutron fields generated by (7)Li(p,n)(7)Be for Gaussian incident protons with mean energy of 1.900 MeV were evaluated at a (7)Li-target thickness t(min). The main evaluation index applied in this study was the treatable protocol depth (TPD) which corresponds to the depth in an irradiated medium that satisfies the requirements of the adapted dose protocol. A maximum TPD (TPD(max)) was obtained for each irradiation condition from the relationship between the TPD and the thickness of boron dose enhancer (BDE) used. For a mono-energetic 1.900 MeV proton beam, the deepest TPD(max) of 3.88 cm was attained at the (7)Li-target thickness of t(min) and a polyethylene BDE of 1.10 cm. When the intended TPD for a BNCT clinical treatment is shallower than the deepest TPD(max), the usable (7)Li-target thickness would be between t(min) and an upper limit t(upper) whose value depends on the BDE thickness used. In terms of the effect of stability of the incident proton energy, Gaussian incident proton energies stable to within +/-10 keV of 1.900 MeV were found to be feasible for the neutron production via the near-threshold (7)Li(p,n)(7)Be reaction for BNCT provided that a suitable BDE is used.

Biophysical Phenomena↗

PubMed2003

Molecular basis and evolutionary origins of color diversity in great star coral Montastraea cavernosa (Scleractinia: Faviida).

Natural pigments are normally products of complex biosynthesis pathways where many different enzymes are involved. Corals and related organisms of class Anthozoa represent the only known exception: in these organisms, each of the host-tissue colors is essentially determined by a sequence of a single protein, homologous to the green fluorescent protein (GFP) from Aequorea victoria. This direct sequence-color linkage provides unique opportunity for color evolution studies. We previously reported the general phylogenetic analysis of GFP-like proteins, which suggested that the present-day diversity of reef colors originated relatively recently and independently within several lineages. The present work was done to get insight into the mechanisms that gave rise to this diversity. Three colonies of the great star coral Montastraea cavernosa (Scleractinia, Faviida) were studied, representing distinct color morphs. Unexpectedly, these specimens were found to express the same collection of GFP-like proteins, produced by at least four, and possibly up to seven, different genetic loci. These genes code for three basic colors-cyan, green, and red-and are expressed differently relative to one another in different morphs. Phylogenetic analysis of the new sequences indicated that the three major gene lineages diverged before separation of some coral families. Our results suggest that color variation in M. cavernosa is not a true polymorphism, but rather a manifestation of phenotypic plasticity (polyphenism). The family level depth of its evolutionary roots indicates that the color diversity is adaptively significant. Relative roles of gene duplication, gene conversion, and point mutations in its evolution are discussed.

Animals↗

PubMed2000

Influence of water table decline on growth allocation and endogenous gibberellins in black cottonwood.

Cottonwoods occur in riparian areas where water table depth generally varies with the elevation of the adjacent river. Plant adaptation to the riparian zone requires the coordination of root elongation to maintain contact with the water table during the summer decline. We investigated the effects of rate of water decline on growth allocation and concentrations of endogenous gibberellins (GAs) in black cottonwood (Populus trichocarpa Torr. & A. Gray ex Hook.) saplings. Rhizopods were used to achieve water decline rates of 0, 2 and 4 cm day(-1). Root elongation approximately doubled in response to the 2 cm day(-1) treatment, whereas leaf area was reduced. A water decline rate of 4 cm day(-1) led to water stress, as evidenced by reduced growth, increased leaf diffusive resistance, decreased water potential, and leaf senescence and abscission. Endogenous GAs were extracted, purified and analyzed by gas chromatography-selected ion monitoring with internal [(2)H(2)]GA standards. Across the sampled plant organs, GAs were generally highest in shoot tips and sequentially lower in basal stems, root tips, leaves and upper roots; GAs were thus abundant in rapidly growing tissues. Of the GAs measured, GA(1) tended to predominate, followed sequentially by GA(3), GA(8), GA(19), GA(20), GA(29) and GA(4). There was little relationship between GA concentration and growth allocation across the water table decline treatments, although GA(8) was consistently reduced in plants experiencing water table decline. Because GA(8) is the final gibberellin in the metabolic sequence, it might be useful for assessing historic patterns of GAs and growth rate. This study demonstrated changes in growth allocation in response to water table decline, but provided little evidence that endogenous GAs play a primary role in the regulation of root elongation in response to water table decline.

Journal Article↗

PubMed2004

Effect of obturation technique on sealer cement thickness and dentinal tubule penetration.

AIM: To compare the average sealer cement film thickness and the extent and pattern of sealer penetration into dentinal tubules in association with four obturation techniques in curved root canals. METHODOLOGY: Mesial canals of 44 extracted mandibular molars were randomly divided among the SimpliFill, continuous wave, Thermafil and 0.04 matched taper (master cones) lateral compaction obturation groups (22 canals per group). AH26 sealer cement was coloured blue-black using Sudan Black B dye. Roots were sectioned 1, 3 and 5 mm from the working length. Specimens were photographed under 25x magnification, mounted as 35 mm slides and projected. Average sealer cement thickness (measured at 10 points around the canal wall), depth of dentinal tubule penetration and frequency of voids were determined at the 1, 3 and 5 mm levels. Data were analysed statistically for effect of obturation technique and level of section on sealer thickness and on the depth and distribution of tubule penetration. RESULTS: Thermafil demonstrated superior GP adaptation at all levels with a mean overall sealer cement thickness of 2.2 microm, followed by lateral compaction (11.1 microm), continuous wave (12.2 microm) and SimpliFill (47.6 microm). SimpliFill also demonstrated the highest frequency of voids (P < 0.05). Sealer cement penetrated dentinal tubules as far as the outer one-third of dentine, with greater penetration observed buccally or lingually (P < 0.001). Penetration was not significantly affected by obturation technique, but on average was deeper and more frequent at the 3 and 5 mm levels than at the 1 mm level (P < 0.001). CONCLUSIONS: Sealer thickness was strongly dependent on obturation technique. Assuming that minimal sealer thickness and fewer voids are good measures of long-term sealing ability, Thermafil resulted in the best outcome. Consistent, extensive sealer penetration into dentinal tubules was seen and was unrelated to the obturation technique.

Bismuth↗

PubMed2025

Radiation Without Borders: Unraveling Bystander and Non-Targeted Effects in Oncology.

Radiotherapy (RT) remains a cornerstone of cancer treatment, offering spatially precise cytotoxicity against malignant cells. However, emerging evidence reveals that ionizing radiation (IR) exerts biological effects beyond the targeted tumor volume, manifesting as radiation bystander effects (BEs) and other non-targeted effects (NTEs). These phenomena challenge the traditional paradigm of RT as a localized intervention, highlighting systemic and long-term consequences in non-irradiated tissues. This comprehensive review synthesizes molecular, cellular, and clinical insights about BEs, elucidating the complex intercellular signaling networks gap junctions, cytokines, extracellular vesicles, and oxidative stress that propagate damage, genomic instability, and inflammation. We explore the role of mitochondrial dysfunction, epigenetic reprogramming, immune modulation, and stem cell niche disruption in shaping BEs outcomes. Clinically, BEs contribute to neurocognitive decline, cardiovascular disease, pulmonary fibrosis, gastrointestinal toxicity, and secondary malignancies, particularly in pediatric and long-term cancer survivors. The review also evaluates countermeasures including antioxidants, COX-2 inhibitors, exosome blockers, and FLASH RT, alongside emerging strategies targeting cfCh, inflammasomes, and senescence-associated secretory phenotypes. We discuss the dual nature of BEs: their potential to both harm and heal, underscoring adaptive responses and immune priming in specific contexts. By integrating mechanistic depth with translational relevance, this work posits that radiation BEs are a modifiable axis of RT biology. Recognizing and mitigating BEs is imperative for optimizing therapeutic efficacy, minimizing collateral damage, and enhancing survivorship outcomes. This review advocates for a paradigm shift in RT planning and post-treatment care, emphasizing precision, personalization, and systemic awareness in modern oncology.

Humans↗

PubMed2000

Clinical and microbiologic study of periodontal surgery by means of apically positioned flaps with and without osseous recontouring.

In periodontitis lesions with interproximal craters, periodontal flap surgery with osseous recontouring allows more apical positioning of the soft periodontal tissue than flap surgery without osseous recontouring. The present study determined the clinical and microbiologic responses to periodontal surgery with and without osseous recontouring in adult periodontitis lesions with interproximal craters. In 7 osseous surgery patients, osteoplasty and ostectomy were performed from the lingual/palatal aspect to eliminate interproximal osseous defects and to partly mimic the original alveolar bony transition to neighboring teeth. In 7 nonosseous surgery patients, the surgical flap was adapted to the preexisting osseous level. Clinical monitoring included periodontal probing depth, Plaque Index, gingival bleeding index, and radiographic examination. Samples of the subgingival microbiota were examined. In sites treated with osseous surgery, mean pocket depth was 5.5 mm at baseline, 1.9 mm at 1 month, 2.0 mm at 3 months, and 2.1 mm at 6 months. In sites not receiving osseous recontouring surgery, the corresponding pocket depths were 5.9 mm, 3.1 mm, 3.8 mm, and 4.1 mm. At baseline in the osseous surgery group, Actinobacillus actinomycetemcomitans was recovered from one patient and Porphyromonas gingivalis from 5 patients; posttreatment, these microbiota were not detected in any patient. In the nonosseous surgery group, the presence of A actinomycetemcomitans increased posttreatment, and levels of P gingivalis remained essentially unchanged after therapy. This study suggests that in patients not receiving adjunctive antibiotic therapy, apically positioned flap surgery with osseous recontouring is more effective than apically positioned flap surgery without osseous recontouring in reducing periodontal pocket depth and levels of major periodontal pathogens.

Adult↗

PubMed2001

Improving botulinum toxin therapy for palmar hyperhidrosis: wrist block and technical considerations.

Botulinum A exotoxin has become an excellent therapeutic option to treat focal hyperhidrosis, but when the problem affects the palmar region the technique has some drawbacks. Pain with injection is difficult to tolerate and the large dose needed to treat both hands are two concerns, as well as muscle weakness secondary to botulinum toxin diffusion and the possibility of antibody production. All these problems limit the number of patients treated. The author's suggestion is to treat only the dominant hand, after performing a wrist block. The use of a device adapted from a cartridge rubber may help to control the injection depth and the risk of muscular weakness.

Botulinum Toxins, Type A↗

PubMed2003

[Imaging the lacrimal canaliculus with 20-MHz ultrasonography: a normal diagnosis (Part 1)].

INTRODUCTION: High-frequency ultrasonography is used in ophthalmology with probes at 20, 30 and 50 MHz. The latter are used particularly for examining the anterior segments of the eye. The physical and acoustic parameters of the 20-MHz probes present an ideal compromise between resolution and penetration depth for examination of the lacrimal passages. These probes can be adapted to the I3 ultrasound diagnostic device, offering a clear financial advantage. MATERIAL AND METHODS: During the ultrasound examination, the patient is in the supine position with the head back and turned away from the eye to be examined. For proper transmission, enough gel must be applied, so that the 20-MHz probe can easily navigate on the surface to be scanned. If there is no inflammation, Healon can be applied in the canal so that it is dilated and easier to visualize. RESULTS: In all patients, we were able to visualize the canaliculi in the main cross-sections with the ultrasound. The edge of the eyelid, the lacrimal caruncle, and the medial palpebral ligament can serve as landmarks in the search for the canaliculi. CONCLUSION: The 20-MHz probes are better adapted to visualizing the presaccular lacrimal passages than conventional 10-MHz probes and the 50-MHz biomicroscope, thus enhancing the spectrum of imaging methods.

Equipment Design↗

PubMedDate not supplied

Microtensile bond strength of tooth-colored materials to primary tooth dentin.

PURPOSE: This study measured the microtensile bond strengths of 2 tooth-colored restorative materials with and without conditioning of primary teeth dentin, and examined the micromorphology of the debonded surfaces and material-dentin interfaces. METHODS: Cylindrical specimens of packable composite resin (PCR) and resin-modified glass ionomer cement (RMGIC) bonded to dentin of primary teeth were ground to an hourglass shape and tested for microtensile bond strength. The debonded surfaces and material-dentin interfaces were prepared and examined under a scanning electron microscope (SEM). RESULTS: The microtensile bond strength values (mean +/- SD, in MPa) of PCR (Filtek P60 with Single Bond) and RMGIC (Fuji II LC), with or without the application of Cavity Conditioner (14.8 +/- 5.36, 12.01 +/- 4.43, 11.94 +/- 4.60, respectively), did not differ significantly (P > .05). Partial adhesive and partial cohesive failures within the restorative material predominated. The distributions of failure modes did not differ significantly between groups (P > .05). Under SEM, each material was seen to be closely adapted to dentin. Dentinal tubules were enlarged with etching, and the depth of penetration of resin tags of PCR was greater than for RMGIC. Smear plugs were incompletely removed by cavity conditioning. CONCLUSIONS: The bond strength of the PCR, Filtek P60 with Single Bond, to dentin of primary teeth was comparable to that of the RMGIC, Fuji II LC. Conditioning of the cavity preparation with Cavity Conditioner did not improve the bond strength of Fuji II LC. The distribution of failure modes did not differ between materials.

Acid Etching, Dental↗

PubMed1998

Our classification of tympanic retraction pockets.

A classification of tympanic retraction pockets is indispensable in order to standardise their evaluation. In this manner, the evolution of the pathology can be carefully followed and the most appropriate therapy chosen. The authors propose adapting their classification to endoscopy which permits the inspection of the depths of certain pockets, otherwise invisible to examination under microscope, thus ensuring a better follow-up.

Ear Diseases↗

PubMed1994

Patterns of coping and characteristics of high-functioning incest survivors.

An exploratory study using a phenomenological approach was designed to examine methods of coping and adaptation that may facilitate a healthy adjustment after sexual abuse. In-depth interviews were conducted with a sample of 15 high-functioning adult female incest survivors. The results identify the capacity of sexually abused children to use avoidance strategies and use psychological escape mechanisms to cope with the abuse; and helped explicate the adult process of separation, self-discovery, and revisiting the past trauma. The victim's cognitive appraisals and responses emerged as important variables in managing the trauma of sexual abuse. The capacity to protect the integrity of the self appeared central to the adult developmental process of integrating the incest experience.

Adaptation, Psychological↗

PubMed2004

Maturation of crack patterns.

Superficial (two-dimensional) crack patterns appear when a thin layer of material elastically attached to a substrate contracts. We study numerically the maturation process undergone by these crack patterns when they are allowed to adapt in order to reduce its energy. The process models the evolution in depth of cracks in geological formations and in starch samples ("columnar jointing"), and also the time evolution (over thousands of years) of crack patterns in frozen soils. We observe an evolution towards a polygonal pattern that consists of a fixed distribution of polygons with mainly five, six, and seven sides. They compare very well with known experimental examples. The evolution of one of these "mature" patterns upon reduction of the degree of contraction is also considered. We find that the pattern adapts by closing some of the cracks and rearranging those in the immediate neighborhood. This produces a change of the mean size of the polygons, but remarkably no changes of the statistical properties of the pattern. Comparison with the same behavior recently observed in starch samples is presented.

Journal Article↗

PubMed1983

The neural signal for skin indentation depth. II. Steady indentations.

The glabrous skin of the monkey's hand was stimulated with a waveform that indented the skin at a rate of 0.4 mm/sec, held the skin steadily or nearly steadily indented for 12 sec or longer, and then retracted back to the starting position. Recordings were made of activity in single afferent fibers in response to these stimuli. The average discharge frequency of 21 slowly adapting mechanoreceptors declined 38% during the first 12 sec of a steady indentation when the amplitude of the displacement was 0.65 mm and 36% when the displacement was 1.3 mm. When the plateau was not steady but the indentation depth gradually decreased by 15% during the 12-sec plateau period, the average decline was 47% for the 0.65-mm indentation and 46% for the 1.3-mm stimulus. When the indentation depth gradually increased by 15% during the 12-sec plateau, the discharge declined an average of 26% during the 0.65-mm indentation and 22% during the 1.3-mm displacement. To determine the effect of receptor adaptation on the perception of skin indentation depth, 13 human subjects had the skin of their fingertips indented 1 mm with similar trapezoidal waveform and were asked whether the indentation depth increased or decreased during the plateau portion of the stimulus. Ten of the 13 subjects thought that the indentation depth was increasing when the plateau was steady. The method of limits was then used to determine how much the stimulus had to change for the subject to feel the depth during the plateau as unchanging; i.e., a "perceptual zero."(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗

PubMed1999

The response to prism deviations in human infants.

Previous research has suggested that infants are unable to make a corrective eye movement in response to a small base-out prism placed in front of one eye before 14-16 weeks [1]. Three hypotheses have been proposed to explain this early inability, and each of these makes different predictions for the time of onset of a response to a larger prism. The first proposes that infants have a 'degraded sensory capacity' and so require a larger retinal disparity (difference in the position of the image on the retina of each eye) to stimulate disparity detectors [2]. This predicts that infants might respond at an earlier age than previously reported [1] when tested using a larger prism. The second hypothesis proposes that infants learn to respond to larger retinal disparities through practice with small disparities [3]. According to this theory, using a larger prism will not result in developmentally earlier responses, and may even delay the response. The third hypothesis proposes that the ability to respond to prismatic deviation depends on maturational factors indicated by the onset of stereopsis (the ability to detect depth in an image on the basis of retinal disparity cues only) [4] [5], predicting that the size of the prism is irrelevant. To differentiate between these hypotheses, we tested 192 infants ranging from 2 to 52 weeks of age using a larger prism. Results showed that 63% of infants of 5-8 weeks of age produced a corrective eye movement in response to placement of a prism in front of the eye when in the dark. Both the percentage of infants who produced a response, and the speed of the response, increased with age. These results suggest that infants can make corrective eye movements in response to large prismatic deviations before 14-16 weeks of age. This, in combination with other recent results [6], discounts previous hypotheses.

Adaptation, Physiological↗

PubMed2006

Effect of leptin on intestinal re-growth following massive small bowel resection in rat.

Recent evidence suggests that the adipose tissue-derived cytokine leptin (LEP) is involved in modulation of growth and differentiation of normal small intestine. The purpose of the present study was to evaluate the effects of parenteral LEP on structural intestinal adaptation, cell proliferation and apoptosis in a rat model of short bowel syndrome (SBS). Male Sprague-Dawley rats were divided into three experimental groups: Sham rats underwent bowel transection and re-anastomosis, SBS-rats underwent a 75% small bowel resection, and SBS-LEP-rats underwent bowel resection and were treated with LEP given subcutaneously at a dose of 20 mug/kg, once daily, from day 3 through 14. Parameters of intestinal adaptation (bowel and mucosal weights, mucosal DNA and protein, villus height and crypt depth in jejunum and ileum), enterocyte proliferation and enterocyte apoptosis were determined on day 15 following operation. Ileal tissue samples were taken for detection of bax and bcl-2 gene expression using RT-PCR technique. Statistical analysis was performed using the non-parametric Kruskal-Wallis ANOVA test, with P<0.05 considered statistically significant. Treatment with subcutaneous LEP resulted in a significant increase in jejunal (17%, P<0.05) and ileal (13%, P<0.05) bowel weight, jejunal (10%, P<0.05) and ileal (25%, P<0.05) mucosal weight, jejunal (26%, P<0.05) and ileal (38%, P<0.05) mucosal DNA, ileal (25%, P<0.05) mucosal protein, jejunal (41%, P<0.05) and ileal (21%, P<0.05) villus height, jejunal (37%, P<0.05) crypt depth, and jejunal (24%, P<0.05) and ileal (21%, P<0.05) enterocyte proliferation compared to SBS-animals. Enterocyte apoptosis increased significantly after bowel resection in jejunum and ileum compared to sham animals and was accompanied by an increased bax gene expression and a decreased bcl-2 gene expression in ileal samples. SBS-LEP rats showed a trend toward a decrease in enterocyte apoptosis in ileum and a mild decrease in bax gene expression compared to SBS-untreated animals. In conclusion, in a rat model of SBS parenteral LEP stimulates structural intestinal adaptation. Increased cell proliferation and decreased cell death via apoptosis may be responsible for this increased cell mass.

Adaptation, Physiological↗

PubMedDate not supplied

The sexual adaptation of women treated for endometrial cancer.

This study explores the process of sexual adaptation in women treated for endometrial cancer. Methodology was primarily qualitative with in-depth interviews. Data were collected by means of semistructured tape-recorded interviews; detailed field notes; and quantitative measures of self-concept, self-esteem, body image, and satisfaction with sexual functioning. The quantitative instruments used to measure these constructs were the Tennessee Self-Concept Scale and three visual analog scales. A vivid picture of women's experience of sexual adaptation after treatment for endometrial cancer emerged. This study's findings indicate that the experience of sexual adaptation in women who undergo treatment for endometrial cancer is a process that evolves. This process begins with the onset of symptoms and continues beyond the completion of therapy. Factors that enhanced the adaptational process were identified by the participants.

Adaptation, Psychological↗

PubMed2000

Adaptational process of parents of pediatric oncology patients.

This study, based on grounded theory, explores the adaptational process of parents of pediatric oncology patients. Thirty-two Taiwanese parents (26 mothers and 6 fathers) were interviewed. Data were collected through individual in-depth and focus group interviews, observations, medical chart review, nurses' note, and researchers' reflexive journals. The findings suggest that parents adapt to their children's cancer by a dynamic process; i.e., they modify their coping tasks and related strategies as clinical events (e.g., diagnosis, side effects, relapses, or death) occur. This adaptational process consisted of five components: confronting treatment, maintaining family integrity, establishing support, maintaining emotional well-being, and searching for spiritual meaning. Related factors such as coping tasks are described.

Adaptation, Psychological↗

PubMed1986

M-wave of proximal retina in cat.

There has been relatively little known about responses from proximal retina in mammals that could contribute to the electroretinogram (ERG). Recently, there has been evidence that the proximal retina is involved in generating the pattern electroretinogram (PERG). In the present work we investigated proximal retinal activity in the intact cat eye during light adaptation. Extracellular potentials evoked in response to circular spots of light, flashed on steady backgrounds, were recorded with microelectrodes placed intraretinally at different depths. Prominent negative responses were found in proximal retina that could be identified as the M-wave previously observed only in cold-blooded retinas. Like the cold-blooded responses, the cat's M-wave consisted of negative-going potentials at stimulus onset and offset that were maximum in amplitude with small spots. By analogy to the cold-blooded data, the cat M-wave is presumed to be the extracellular voltage arising from Müller cell responses to K+ released by proximal retinal neurons. In addition, the cat M-wave only appeared with backgrounds at and above rod saturation and had short latencies (30 ms) at stimulus onset and offset, indicating that it is a cone-driven response. The M-wave could be clearly distinguished from PII (b-wave and DC component) on the basis of its form, depth distribution, and stimulus-response characteristics. For example, photopic PII had its maximum voltage in the distal retinal at 55% retinal depth, whereas the M-wave was maximal in the proximal retina at 25% retinal depth. Also, PII simply increased in amplitude as stimulus spots were enlarged, whereas the M-wave exhibited spatial tuning. Under light-adapted conditions and with small-spot stimuli the M-wave is the largest extracellular voltage in cat retina. By recording the vitreal ERG near the retinal surface with the microelectrode referenced to a silver wire in the vitreous, we found that the M-wave in response to a small spot always had a negative polarity in the vitreous. Thus, unlike PII, the M-wave does not reverse polarity at the vitreo-retinal border. Because of stray-light effects, however, we were not able to assess the amplitude of the M-wave's contribution to the ERG obtained with diffuse retinal illumination. We conclude that the M-wave is present in the cat as a prominent cone-driven response of proximal retina that is separate from the b-wave, and whose significance for electroretinographic recordings remains to be determined.

Adaptation, Ocular↗