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At least 1,153 records · Page 64Linked to original sources
PubMed2005

High-energy (nanojoule) femtosecond pulse delivery with record dispersion higher-order mode fiber.

Delivery of high peak-power femtosecond pulses with fibers is constrained by nonlinear distortions accumulated during pulse propagation. We address this problem with a novel, to our knowledge, fiber schematic, where the pulse propagates in a small Aeff (18 microm2) but highly dispersive (record value of approximately -900 ps/nm km) medium, enabled by transmission in the LP02 mode of a few-mode fiber. The novel fiber yields a low dispersion-to-nonlinear-length ratio (due to its large dispersion) despite its small Aeff, hence enabling mitigation of nonlinearities. This enables fiber delivery of distortion-free <150 fs, approximately 1 nJ, and 840 nm pulses--an order-of-magnitude improvement over single-mode fibers of similar Aeff.

Equipment Design↗
PubMed2006

Low bone mass in children and adolescents.

Osteoporosis is a disease characterized by low bone mass and micro architectural alterations of bone tissue leading to enhanced bone fragility and increased fracture risk. Although research in osteoporosis has focused mainly on the role of bone loss in the elderly population, it is becoming increasingly clear that the amount of bone that is gained during growth is also an important determinant of future resistance to fractures. Thus, considerable interest is being placed on defining preventive strategies that optimize the gain of bone mass during childhood and adolescence. Knowledge of the determinants accounting for the physiologic and genetic variations in bone accumulation in children will provide the best means toward the early diagnosis and treatment of osteoporosis. This article reviews the techniques available for bone mass measurements in children and the major determinants and diseases influencing bone accretion during childhood and adolescence.

Absorptiometry, Photon↗
PubMed2004

Simulating the interactions of toxins with K+ channels.

Toxins have been important tools to characterize the structures and functions of K+ channels in recent years due to their unique blockage of the K+ current and other physiological functions to the K+ channels, especially the voltage-gated K+ channels. Knowledge of the interacting surfaces between the toxins and the channels has been accumulated both from biological explorations and theoretical simulations. It has been found that the electrostatic potentials act as the driving force for the recognition of the toxins with the channels, and the orientation of the toxins over the channels follows the direction of the dipole moment. The binding site is composed most of the conservative residues of the negatively charged rings of Asp/Glu and residues around the edge of the central pore. The selectivity mainly comes from the type and distribution of the positive charged residues, and the whole topologies of the toxins. Based on the molecular determinants of the complex formation, and taking advantage of the structure-based methodologies of molecular design, it is hopefully to develop new generation of lead compounds specifically binding with subtypes of K+ channels.

Amino Acid Sequence↗
PubMed1990

Possible role of pineal melatonin in the mechanisms of aging.

The pineal gland has captured man's attention as early in recorded history as the Greeks when philosophers considered it the "seat of the soul". Descartes, in the Middle Ages, furthered this concept naming it "esprits animaux" or, in current language, the psychic and somatic activating principle. These notions about the pineal gland were initially purely speculative and unsupported by scientific facts. However, with the development of a sound knowledge base concerning the pineal gland over the past twenty years, evidence has accumulated to suggest a pivotal role for the pineal in the 'fine tuning' and integrating of various neural and endocrine functions. The secretion of pineal melatonin has been shown to decline progressively with age. Recent hypotheses of aging have suggested that cumulative neuronal insults associated with free radical production may be associated with the process of aging. There is evidence to suggest that melatonin may protect against the age processes in part by attenuating the effects of free radical-induced neuronal damage. Other studies derived mainly from observations on pinealectomized rats also suggest that diminished melatonin secretion may be associated with acceleration of the aging process. Thus, pineal melatonin may be a natural anti-aging hormone.

Aging↗
PubMed1990

pKa values and partition coefficients of nitroxide spin probes for membrane bioenergetics measurements.

Knowledge of pKa's is necessary to calculate intracellular/intravesicular pH values from nitroxide accumulation in cells or vesicles as detected with electron spin resonance (ESR) spectroscopy. pKa values were confirmed in lipid vesicles of known internal pH. To help select probes that do not accumulate in lipid membranes, octanol/buffer partition coefficients of uncharged nitroxides were determined. As an application of selected probes, pH gradients and internal aqueous volumes were analyzed in mitochondria (one internal compartment) and in the cyanobacterium Synechococcus 6311 (two internal compartments). The combination of 3-carboxy-, 3-amino- and 3-aminocarbonyl-2,2,5,5-tetramethylpyrrolidin-1-yloxyl was found to be most satisfactory for determinations of internal pH and volumes.

Animals↗
PubMed1984

Association of beta hydroxybutyric acidosis with isoniazid intoxication.

Acute metabolic acidosis associated with accumulation of lactate has been previously reported in isoniazid (INH) intoxication. To our knowledge, association of INH toxicity with beta-hydroxybutyric acidosis has not been demonstrated previously. The present report documents the occurrence of beta-hydroxybutyric acidosis in patients with INH intoxication. The reason for the lack of previous reports of this association is not clear, although failure to measure plasma beta-hydroxybutyrate levels in previous studies is a likely possibility. Our patients received intravenous sodium bicarbonate, anticonvulsants and dialysis which resulted in complete reversal of metabolic acidosis and other manifestations of INH toxicity.

3-Hydroxybutyric Acid↗
PubMed1977

Hydrogen sulfide poisoning: review of 5 years' experience.

The workforce of Alberta, a province rich in fossil fuel, faces an increasing risk of exposure to hydrogen sulfide (H2S). Basic knowledge of the population exposed during the years 1969 to 1973 inclusive was accumulated to identify the immediate medical and management problems. Data were recorded from three sources of records: the Workers' Compensation Board of Alberta, the Alberta Hospital Services Commission and the provincial coroner's office. There were 221 cases of exposure to H2S. The overall mortality was 6%; 5% of victims were dead on arrival at hospital. Admission to hospital was required for 65% of the victims arriving at a hospital emergency room (78% of the 221). Acute problems were coma, dysequilibrium and respiratory insufficiency with pulmonary edema. Increased attention to cardiopulmonary resuscitation at the exposure site and during transportation to hospital is necessary to reduce the mortality from H2S exposure. No long-term adverse effects were apparent in the survivors.

Accidents, Occupational↗
PubMedDate not supplied

The cellular history of the glomerulus.

Knowledge about the structure and functions of the cells of the glomeruli has accumulated slowly over the past 350 years. Marcello Malpighi originated the work, but it failed to progress far until Schleiden and Schwann developed their cellular theory in 1839. William Bowman linked the glomeruli to the tubules, described the parietal epithelial cells, the basement membranes, and (with Robert Todd) apparently first identified endothelial cells. Electron microscopy contributed especially to an understanding of epithelial and endothelial cell structure. Axel Key first described mesangial cells, but acceptance of these fell into abeyance for many years until Yamada incontrovertibly demonstrated their existence. Techniques such as tissue culture and molecular biological investigations have, more recently, provided much information about glomerular cell function. Progress has, throughout, depended upon the discovery of ever more powerful methods of microscopy, the development of ancillary experimental methods, the formulation of persuasive explanations for observations, and the suggestion of succinct terminology to describe the features observed.

History, 17th Century↗
PubMedDate not supplied

A study of oro-dental disorder in the area of Rural Health Training Centre, Naila (Jaipur).

A door to door survey on oro-dental disorders was carried out in four villages of the field practice area of Rural Health Training Centre, Naila (Jaipur), covering a population of 1384 in the age group of 6 years and above. A total of 81 (5.85 per cent) of the examined population had malocclusion, and its relationship with age was found to be significant (P less than 0.01). A highly significant (P less than 0.001) increase was observed in oral-mucosal and dental disorder with advance in age. Among the dental disorders, dental caries was most common, affecting 15.32 per cent of the total population followed by fluorosis (1.66 per cent), attrition of teeth (0.94) per cent) and supernumerary (0.58 per cent). A statistically highly significant (p less than 0.001) difference was observed in prevalence of attrition, dental fluorosis and caries with age. The facts accumulated during the survey bring out vividly the need to apply the growing knowledge on orodental health. The need is not only for treatment, but also prevention and education about oral hygiene.

Adolescent↗
PubMed1981

[Lysosomal glycosidases and glycoproteinoses].

The development of chemicall, physical and enzymatic methods lead to the determination of numerous structures of glycoprotein glycans and allowed to classify them into "structural families". On the basis of this knowledge, it has been possible, 1) to demonstrate that the oligosaccharides and glycoasparagines accumulating in tissues and urines of patients with diseases characterized by a lack in lysosomal glycosidases originate from glycoprotein glycans incompletely catabolized; 2) to propose a scheme for the normal and pathological catabolism of glycoproteins and 3) to elucidate the problem of the origin of lysosomal glycosidases. These latter are internalized into the lysosomes either through a mechanism of secretion-reuptake, or by following an intracellular traffic, or via the cell plasma membrane. In al cases, membrane receptors intervene which specifically recognize phosphorylated oligomannosidic structures carried by the acidic hydrolases.

Carbohydrate Metabolism, Inborn Errors↗
PubMed1996

[Ca2+ -ATPase].

The importance of the Ca2+ -ATPases of the surface and endoplasmic reticulum membranes in regulating the intracellular Ca2+ concentrations in living cells has been recognized as a result of the development of biophysical techniques and finding of useful pharmacological tool drugs. The number of possible isoforms of these Ca2+ -ATPases are increased by a complex pattern of alternative splicing and the knowledge of the functional difference and tissue distribution of these isoforms has been accumulated. In this review, we discuss recent progress in our understanding of the roles of the Ca2+ -ATPases in physiological and pathophysiological conditions.

Animals↗
PubMed1998

Technetium-99m-tetrofosmin scintigraphy in pulmonary tuberculosis.

UNLABELLED: Technetium-99m-tetrofosmin, an agent that is widely used in myocardial imaging, has been reported to accumulate in several types of malignancies, including lung tumors. Yet, there is limited knowledge about its role in imaging infection or inflammatory lesions. The aim of this study was to investigate the role of 99mTc-tetrofosmin scintigraphy in pulmonary tuberculosis in cases with active and inactive tuberculosis in comparison with radiological and microbiological findings. METHODS: Twenty-seven patients with active pulmonary tuberculosis (APTB) and 6 patients with inactive pulmonary tuberculosis (IPTB), proven by sputum smears and cultures, were included in this study. Mean age of the group was 42.6+/-13 yr. Nine months after therapy, 99mTc-tetrofosmin scintigraphy was repeated in 6 patients with APTB to evaluate response to therapy. Ten-minute anterior and posterior chest images were acquired 20 and 60 min after the injection of 370 MBq (10 mCi) 99mTc-tetrofosmin. The images were evaluated both visually and semiquantitatively by two blinded nuclear medicine physicians. For semiquantitative evaluation, regions of interest (ROIs) were drawn over the lesion (L) and nonlesion areas (NL). The mean count values of ROIs were obtained and L/NL ratios were calculated. RESULTS: According to the visual evaluations, 99mTc-tetrofosmin uptake was Grade (+) in 4 (15%) and Grade (++) in 23 (85%) patients with APTB. Technetium-99m-tetrofosmin uptake was negative in 5 patients with IPTB. Grade (+) 99mTc-tetrofosmin uptake was observed in only one inactive case. After therapy, there was no 99mTc-tetrofosmin uptake in 3 patients, which correlated well with chest radiography and clinical findings. In the other 2 patients, 99mTc-tetrofosmin uptake was slightly decreased when compared with a previous scan that correlated with radiological and clinical findings. In 1 patient with bilateral lung disease, 99mTc-tetrofosmin uptake decreased on the right lung lesions, whereas the left lung lesions persisted with no change. The mean early and delayed L/NL ratios of APTB were 1.53+/-0.22 and 1.45+/-0.21, respectively. Although 99mTc-tetrofosmin uptake in APTB lesions was more visually marked in early images than that in delayed images, there was no statistically significant difference between these two sets of images. CONCLUSION: Technetium-99m-tetrofosmin scintigraphy showed increased uptake in APTB lesions related to disease activity. After treatment, 99mTc-tetrofosmin uptake disappeared or decreased, correlating well with radiological and clinical findings. Technetium-99m-tetrofosmin scintigraphy may have a complementary role in the assessment of APTB as well as in follow-up treatment.

Adolescent↗
PubMed2005

Late-onset MNGIE due to partial loss of thymidine phosphorylase activity.

Mitochondrial neurogastrointestinal encephalomyopathy (MNGIE) is caused by mutations in the gene encoding thymidine phosphorylase (TP). All MNGIE patients have had severe loss of TP function and prominent plasma accumulations of the TP substrates thymidine (dThd) and deoxyuridine (dUrd). Here, we report for the first time to our knowledge three MNGIE patients with later onset, milder phenotype, and less severe TP dysfunction, compared with typical MNGIE patients. This report demonstrates a direct relationship between the biochemical defects and clinical phenotypes in MNGIE and supports the notion that reduction of dThd and dUrd accumulation or TP replacement could be useful therapy for MNGIE.

Arginine↗
PubMedDate not supplied

Implementation of intensity-modulated radiation therapy in head and neck tumors: what are the important data for biological optimization?

Intensity-modulated radiation therapy (IMRT) for head and neck (HN) tumors refers to a new approach to the whole treatment procedure from patient immobilization to beam delivery. Implementation of IMRT thus requires knowledge of setup uncertainties, adequate selection and delineation of target volumes based on optimal imaging modalities, appropriate specification and dose prescription regarding dose-volume constraints, and ad hoc quality control of both the clinical and physical aspects of the whole procedure. A large number of issues still need to be resolved and/or further refined. In particular, data need to be accumulated in a better integration of improved dose distribution into the fractionation strategy, and in-depth knowledge of dose-volume constraints for normal tissues at risk. In this article, these issues will be reviewed and put into the prospective of IMRT treatment.

Dose Fractionation, Radiation↗
PubMed2004

New knowledge of the pathogenesis of periodontal disease.

The aim of this study was to evaluate the relationship between the accumulation of interleukins IL-1beta, TNF-alpha, IL-8, and chemokine RANTES (Regulated upon Activation Normal T-cell Expressed and Secreted) in gingival fluid and periodontal support tissues in patients with periodontitis. A review is also provided of apoptotic processes as events of major importance, highlighting the presence of TUNEL cells and ultrastructural morphologic changes associated with cell apoptosis. There appears to be further evidence to support the important role of inflammation control. Cytokines may be considered as markers of the progression and severity of periodontitis as well as indicators of an appropiate response to treatment. However, further studies are needed to support and characterize this concept.

Antigens, Bacterial↗
PubMed2006

Black thyroid resulting from short-term doxycycline use: case report, review of the literature, and discussion of implications.

BACKGROUND: Black thyroid pigmentation has been considered pathognomonic for chronic minocycline ingestion for more than 30 years. Although never conclusively linked to overt disease, evidence clearly exists that minocycline is a competitive inhibitor of thyroid peroxidase in metabolically active thyroid tissue. This offers a potential mechanism of pigment accumulation, which can account for the occasional finding of hypopigmentation in thyroid carcinomas. To our knowledge, an association with tetracycline derivatives other than minocycline has not been documented. METHODS: Herein is a case report of a patient with gross black thyroid tissue containing a hypopigmented papillary thyroid carcinoma. Twelve days before surgery, the patient was placed on doxycycline, a tetracycline derivative, to optimize an in vitro fertilization regimen. RESULTS: The gross specimen was diffusely black in color with a 1.5-cm hypopigmented focus of papillary thyroid cancer. Hematoxylin-eosin staining, as well as electron micrographs, was consistent with findings associated with minocycline ingestion. CONCLUSIONS: Black thyroid is rare and only previously associated with chronic minocycline ingestion. This report documents a black thyroid in a patient after short-term exposure to doxycycline. Pigment accumulation in normal tissue is thought to occur by inhibition of thyroid peroxidase. Minocycline is a competitive inhibitor of this enzyme in its native configuration. Thyroid carcinomas are known to have abnormal thyroid peroxidase, which could account for reports of hypopigmented tumors within grossly darkened thyroid tissue. Hypopigmented foci within such "black thyroid" deserve through pathologic examination.

Adult↗
PubMed1976

Fine structural observations of the liver in alpha-1-antitrypsin deficiency.

Morphologic studies of liver tissue in individuals deficient in alpha-1-antitrypsin (alpha-1-AT) have established the presence of membrane-delimited deposits which are diastase resistant, perodic acid-Schiff positive, sialic acid deficient, and immunologically related to serum alpha-1-AT. The molecular basis for the accumulation alpha-1-AT-like substance in hepatocytes and the serum deficiency in alpha-1-AT patients is unknown. In an effort to gain insight into the membrane sites involved in the storage of the alpha-1-AT-like material, we examined liver biopsies by light and electron microscopy from 3 children with homozygous PiZZ deficiency and varying degrees of liver pathology. Contrary to the more widely held belief that accumulation occurs primarily in the rough endoplasmic reticulum, we find the earliest and greatest accumulation of alpha-1-AT-like material in smooth endoplasmic reticulum of hepatocytes. We have combined our ultrastructural observations with the current knowledge which is available concerning the structural properties of M-type and Z-type alpha-1-AT and have proposed a model which may explain the basis for the hepatic accumulation of alpha-1-AT-like material and the serum deficiency state in the PiZZ genotypes.

Child↗
PubMed2004

Microarray analysis of Cryphonectria parasitica Galpha- and Gbetagamma-signalling pathways reveals extensive modulation by hypovirus infection.

Using an established spotted cDNA microarray platform, the nature of changes in the transcriptional profiles of 2200 unique genes from the chestnut blight fungus Cryphonectria parasitica in response to the absence of either the Galpha subunit CPG-1 or the Gbeta subunit CPGB-1 has been explored. It is reported that 216 transcripts were altered in accumulation in the Deltacpg-1 strain and 163 in the Deltacpgb-1 strain, with a considerable overlap (100 genes) that were changed in both cases. Of note, these commonly altered transcripts were changed in the same direction in every instance, thus suggesting a considerable redundancy in pathway control or extensive crosstalk. To further knowledge of the potential impact on G-protein-signalling of infection by hypovirus CHV1-EP713, the accumulation of CPG-1 and CPGB-1 was also investigated by Western analysis. It was demonstrated that both signalling components were reduced in abundance to approximately 25 % of wild-type levels, while their transcripts were slightly elevated. Comparison of a list of genes with altered expression in the presence of CHV1-EP713 to the data obtained in the absence of either G-protein subunit showed that more than one-half of all the transcripts changed by hypovirus infection were also changed in at least one G-protein mutant strain, with one-third being changed in both. Significantly, 95 % of the co-changed genes were altered in the same direction. These data provide the first evidence for modulation of Gbeta protein levels as well as the Gbetagamma-signalling pathways by hypovirus infection, and support the hypothesis that modification of G-protein-signalling via both Galpha and Gbetagamma provides for a significant contribution to hypovirus-mediated phenotype.

Ascomycota↗