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At least 307 records · Page 17Linked to original sources
PubMed2007

Effects of subchronic exposure to radio frequency from a conventional cellular telephone on testicular function in adult rats.

PURPOSE: We investigated the effects of subchronic exposure to radio frequency emitted from a conventional cellular telephone on the testicular function in adult rats. MATERIALS AND METHODS: A total of 16 male Wistar rats at age 30 days were randomly divided into 2 groups, including experimental and control groups. The experimental group was exposed to radio frequency emitted from a conventional GSM (global system for mobile communications) cellular telephone (1,835 to 1,850 MHz) for 1 hour daily during 11 weeks. Rectal temperature was measured before and after the exposure period. Testicular and epididymal weight, lipid peroxidation levels in these organs, serum total testosterone and the epididymal sperm count were evaluated. Maturation phase spermatid retention at stage IX-X, interstitial infiltration, cellular vacuolation and multinucleate giant cells were among the qualitative testicular histopathological end points analyzed. Each rat had 10 consecutive round seminiferous tubules at stage VII-VIII evaluated for the mean seminiferous tubular diameter measurement, the crude histological count of round spermatids, pachytene spermatocytes and Sertoli's cells with evident nucleoli, and the true histological count (Abercrombie's correction factor) of round spermatids and pachytene spermatocytes. RESULTS: Mean rectal temperature did not alter following exposure. There was no statistical difference between the control and experimental groups in any end points evaluated. CONCLUSIONS: The current study shows that the low intensity pulsed radio frequency emitted by a conventional cellular telephone does not impair testicular function in adult rats.

Age Factors↗
PubMed1997

In vivo tissue compatibility of two radio-opaque polymeric biomaterials.

Polymeric biomaterials featuring intrinsic radio-opacity continue to attract considerable scientific attention. This work focusses on two polymers that contain covalently bound iodine, rendering the materials radio-opaque. The first material is hard, transparent and glass-like, and consists of methyl methacrylate, 2-(2'-iodobenzoyl)-ethyl methacrylate (1) and 2-hydroxyethyl methacrylate (HEMA), in the molar ratio 65:20:15, respectively. The second material is a cross-linked hydrophilic network, consisting of HEMA and 1, in the molar ratio 80:20, respectively. Both materials were characterized by means of different physico-chemical techniques, including magic-angle-spinning solid state NMR spectroscopy, infrared spectroscopy and differential scanning calorimetry. Moreover, both materials were implanted subcutaneously in rats for 24 days. Upon explanation and histological examination, it appeared that both materials were well tolerated. No tissue necrosis, abscess formation or inflammation were observed. The samples were found to be surrounded by a vascularized capsule consisting of connective tissue cells. The results reveal excellent tissue compatibility for both materials. This is an important observation, since tissue compatibility is absolutely necessary for the applications which are foreseen for this type of radio-opaque biomaterials.

Animals↗
PubMedDate not supplied

Radio-ablation of advanced grades of hemorrhoids with radiofrequency.

BACKGROUND: For advanced degree of hemorrhoids with prolapse of the rectal mucosa, the choice is hemorrhoidectomy, which could be open, close, diathermy, Laser, or stapled one. As an effective alternative to this, in situ radio-frequency ablation of the pile mass has been found to be quite efficacious with many added advantages over the conventional hemorrhoidectomy procedures in practice. MATERIALS AND METHODS: This study included 50 patients (34 males and 16 females) treated at Gupta Nursing Home, Laxminagar, Nagpur, India, with the above technique from April 2000 to March 2001 and each case followed up over a period of 12 months. RESULTS: In first 4 weeks of the procedure, 14% of patients complained of bleeding, whereas all of the patients had some amount of pain. Eleven (22%) patients had serosanguinous discharge, but in none of them was there any incontinence or prolapse. All of the patients resumed their routine within 1 week of the procedure. A subsequent follow-up of the patients at an interval of 12 weeks and 12 months showed significant relief in all of the above early postoperative symptoms. During follow-up at the end of 1 year, 7 patients were found to have skin tag formation. However, complications like anal stenosis or stricture or incontinence was not found in any of the patients. CONCLUSION: For advanced degree of piles with prolapse as the main symptom, in situ radio-frequency ablation can be a better choice to various types of hemorrhoidectomy in the sense that the hospital stay is minimized, recurrence is rare, and return to work is faster. The results are more assuring when compared with conventional hemorrhoidectomy. The technique fits into the parameters for being called the gold standard procedure. Except the radio-frequency unit, the procedure needs no specialized instrument. It can be performed in any routine surgical setup.

Catheter Ablation↗
PubMed1996

Radio-lunate arthrodesis for distal radial intraarticular malunion.

Eleven cases of symptomatic distal radial intraarticular malunion were treated by radio-lunate arthrodesis from 1983 to 1991. The mean age was 35.3 years. There were 11 men, all manual workers. The mechanism was usually a high velocity injury. The time elapsed since injury was a mean 23 months (2-109 months). The range of motion was, on average, flexion 39 degrees, extension 27 degrees, radial deviation 10 degrees and ulnar deviation 20 degrees. Pain was present on light work and grip strength was 45% of the opposite side. The average step-off was 4.4 mm. The scapho-lunate gap was greater than 3 mm in three cases and 5 mm in one case. An ulnar translation of the carpus greater than 4 mm was present in four cases. Posterior subluxation was significant in three cases. The distal radio-ulnar joint (DRUJ) was totally destroyed in three cases, and incongruent in five. Radio-lunate arthrodesis is performed by a posterior approach. Other procedures were combined, mainly on the DRUJ. The average follow-up was 28.5 months (8-79 months). Healing was achieved in ten out of 11 cases in 45 to 90 days. Pain was absent or moderate after 4 months. The range of motion was 33 degrees in flexion, 39 degrees in extension, 17 degrees in radial deviation and 29 degrees in ulnar deviation. The average post-operative strength was 57% of the opposite side (19 kg/33). Eight patients returned to their previous work and two to lighter work.

Adult↗
PubMed2003

Identity confirmation of 99mTc-MAG3, 99mTc-sestamibi and 99mTc-ECD using radio-LC-MS.

Due to the low concentrations in which 99mTc-radiopharmaceuticals are obtained (4-40 ng/ml), confirmation of the identity of these tracer agents in the European Pharmacopoeia is generally performed only indirectly by assessment of their retention times on RP-HPLC. We have investigated whether it is possible to obtain more direct proof of the identity of technetium-99m labelled radiopharmaceuticals using radio-LC-MS. As representative examples, negatively charged 99mTc-MAG3, positively charged 99mTc-Sestamibi and neutral 99mTc-ECD were used. The three technetium-99m radiopharmaceuticals were prepared in several conditions to obtain variable relative amounts of radiochemical impurities and variable concentrations of the complexes (pico- to nanomolar). The preparations were analyzed on a reversed phase C18 HPLC column using a radio-LC-MS system equipped with a time of flight mass spectrometer with electrospray ionization in positive (99mTc-Sestamibi, 99mTc-ECD) or negative (99mTc-MAG3, 99mTc-ECD) mode. For each of the studied complexes, the main peak in the radiometric channel coincided with the expected molecular ion mass of the corresponding technetium complex in the mass spectrometer channel. The relative error on the measured accurate mass was in the range of 10 ppm. The identity of several radiochemical impurities of the three technetium complexes was also confirmed or established. It is concluded that radio-LC-MS can be a sensitive aid in quality control of 'no carrier added' radiopharmaceuticals.

Chromatography, Liquid↗
PubMed2002

Interstellar scintillation as the origin of the rapid radio variability of the quasar J1819+3845.

The liberation of gravitational energy as matter falls onto a supermassive black hole at the centre of a galaxy is believed to explain the high luminosity of quasars. The variability of this emission from quasars and other types of active galactic nuclei can provide information on the size of the emitting regions and the physical process of fuelling the black hole. Some active galactic nuclei are variable at optical (and shorter) wavelengths, and display radio outbursts over years and decades. These active galactic nuclei often also show faster intraday variability at radio wavelengths. The origin of this rapid variability has been extensively debated, but a correlation between optical and radio variations in some sources suggests that both are intrinsic. This would, however, require radiation brightness temperatures that seem physically implausible, leading to the suggestion that the rapid variations are caused by scattering of the emission by the interstellar medium inside our Galaxy. Here we show that the rapid variations in the extreme case of quasar J1819+3845 (ref. 10) indeed arise from interstellar scintillation. The transverse velocity of the scattering material reveals the presence of plasma with a surprisingly high velocity close to the Solar System.

Journal Article↗
PubMed2002

Observational evidence for the accretion-disk origin for a radio jet in an active galaxy.

Accretion of gas onto black holes is thought to power the relativistic jets of material ejected from active galactic nuclei (AGN) and the 'microquasars' located in our Galaxy. In microquasars, superluminal radio-emitting features appear and propagate along the jet shortly after sudden decreases in the X-ray fluxes. This establishes a direct observational link between the black hole and the jet: the X-ray dip is probably caused by the disappearance of a section of the inner accretion disk as it falls past the event horizon, while the remainder of the disk section is ejected into the jet, creating the appearance of a superluminal bright spot. No such connection has hitherto been established for AGN, because of insufficient multi-frequency data. Here we report the results of three years of monitoring the X-ray and radio emission of the galaxy 3C120. As has been observed for microquasars, we find that dips in the X-ray emission are followed by ejections of bright superluminal knots in the radio jet. The mean time between X-ray dips appears to scale roughly with the mass of the black hole, although there are at present only a few data points.

Journal Article↗
PubMed2005

A size of approximately 1 au for the radio source Sgr A* at the centre of the Milky Way.

Although it is widely accepted that most galaxies have supermassive black holes at their centres, concrete proof has proved elusive. Sagittarius A* (Sgr A*), an extremely compact radio source at the centre of our Galaxy, is the best candidate for proof, because it is the closest. Previous very-long-baseline interferometry observations (at 7 mm wavelength) reported that Sgr A* is approximately 2 astronomical units (au) in size, but this is still larger than the 'shadow' (a remarkably dim inner region encircled by a bright ring) that should arise from general relativistic effects near the event horizon of the black hole. Moreover, the measured size is wavelength dependent. Here we report a radio image of Sgr A* at a wavelength of 3.5 mm, demonstrating that its size is approximately 1 au. When combined with the lower limit on its mass, the lower limit on the mass density is 6.5 x 10(21)M(o) pc(-3) (where M(o) is the solar mass), which provides strong evidence that Sgr A* is a supermassive black hole. The power-law relationship between wavelength and intrinsic size (size proportional, variantwavelength(1.09)) explicitly rules out explanations other than those emission models with stratified structure, which predict a smaller emitting region observed at a shorter radio wavelength.

Journal Article↗
PubMed2002

In vitro chemo- and radio-resistance in small cell lung cancer correlates with cell adhesion and constitutive activation of AKT and MAP kinase pathways.

Most small cell lung cancer (SCLC) patients relapse within 12 months of starting combination chemotherapy plus radio-therapy, due to the development of acquired chemo- and radio-resistance. This phenomenon relates to the induction of tumour differentiation, resulting in apoptosis-resistant, morphologically variant (v-SCLC) cells, which lack the neuroendocrine expression of classic (c-) SCLC cells. In this study spontaneously adherent SCLC sublines were shown by differential gene expression analysis to provide an in vitro model of variant differentiation in SCLC, with down-regulation of neuroendocrine markers and up-regulation of epithelial differentiation markers cyclin D1, endothelin, the cell adhesion molecules CD 44 and integrin subunits alpha2, beta3 and beta4. The sensitivity of adherent SCLC sublines to etoposide, cyclophosphamide and gamma radiation was significantly diminished relative to parent suspension cell lines. Western blot analysis using phosphorylation-specific antibodies to Akt and MAP kinase revealed markedly elevated activation in adherent SCLC sublines, paralleled by increased levels of phosphorylated Bad protein and activated NF-kappaB. Subcultivation of the adherent sublines on uncoated surfaces reversed their adherent phenotype immediately and under these conditions Akt activity reverted to low levels. These results suggest that c-SCLC cells can differentiate spontaneously to v-SCLC and that the associated cellular adhesion may trigger Akt-dependent inhibition of apoptosis in SCLC cells, thus leading to acquired chemo- and radio-resistance.

Antineoplastic Agents↗
PubMed1980

[The value of radio-isotope investigations of the urinary tract for the diagnosis of urinary tract calculi during pregnancy (author's transl)].

According to the literature, urinary tract calculi are a rare complication of pregnancy. Because of the radiation effect of excretory urography on mother and fetus, intravenous pyelography can only rarely be used for the diagnosis of calculi in pregnancy. A sequential radio-isotope nephrogram and the simultaneous determination of the J 131 hippurate clearance equivalents were used in two pregnant patients. The cases are reported. The results are discussed and compared to reports in the literature. The exposure to radiation is about 50 mrem for radio-isotope nephrography compared to from 500 to 4000 mrem for excretory urography. Radio-isotope nephrography is therefore useful for the preliminary diagnosis of urinary tract calculi in pregnancy and the simultaneous clearance determination yields additional data on the function of the urinary tract.

Adult↗
PubMed1995

Structure and evolution of the compact radio source in NGC 1275.

Investigations of the fine-scale structure in the compact nucleus of the radio source 3C 84 in NGC 1275 (New General Catalogue number) are reported. Structural monitoring observations beginning as early as 1976, and continuing to the present, revealed subluminal motions in a jet-like relatively diffuse region extending away from a flat-spectrum core. A counterjet feature was discovered in 1993, and very recent nearly simultaneous studies have detected the same feature at five frequencies ranging from 5 to 43 GHz. The counterjet exhibits a strong low-frequency cutoff, giving this region of the source an inverted spectrum. The observations are consistent with a physical model in which the cutoff arises from free-free absorption in a volume that surrounds the core but obscures only the counterjet feature. If such a model is confirmed, very-long-baseline radio interferometry observations can then be used to probe the accretion region, outside the radio jet, on parsec scales.

Journal Article↗
PubMed1999

Very large radio surveys of the sky.

Recent advances in electronics and computing have made possible a new generation of large radio surveys of the sky that yield an order-of-magnitude higher sensitivity and positional accuracy. Combined with the unique properties of the radio universe, these quantitative improvements open up qualitatively different and exciting new scientific applications of radio surveys.

Journal Article↗
PubMed1982

Phylogenetic analysis of platelet-derived growth factor by radio-receptor assay.

Competition between 125I-labeled platelet-derived growth factor (PDGF) and unlabeled PDGF forms the basis of a specific "radio-receptor assay" for quantifying PDGF in clotted blood serum. Human clotted blood serum contains 15 ng/ml of PDGF by radio-receptor assay; this corresponds to a PDGF content of approximately 7.5 x 10(-5) pg per circulating platelet, a figure which is corroborated by purification data. Clotted blood sera from mammals, lower vertebrates and marine invertebrates were screened for homologues of human PDGF by radio-receptor assay. All tested specimens from phylum Chordata contain a mitogenic agent that competes with human PDGF for receptor binding. Sera from tunicates down on the chordate line of evolution and sera from all tested animals on the arthropod line of development were negative. The phylogenetic distribution of PDGF homologue does not correlate with platelet distribution since platelets and their precursor cell--the bone marrow megacaryocyte--are unique to the mammalian hematopoietic system. One anatomical feature appearing coordinately with PDGF on the vertebrate line of development is a pressurized circulatory system. The coincidental appearance of these features may lend support to the hypothesis that PDGF plays a role in maintenance and repair of the vascular lining in vivo.

Animals↗
PubMed1999

NICMOS Imaging of the Dusty Microjansky Radio Source VLA J123642+621331 at z = 4.424.

We present the discovery of a radio galaxy at a likely redshift of z=4.424 in one of the flanking fields of the Hubble Deep Field (HDF). Radio observations with the Very Large Array and MERLIN centered on the HDF yielded a complete sample of microjansky radio sources, of which about 20% have no optical counterpart to I</=25 mag. In this Letter, we address the possible nature of one of these sources through deep Hubble Space Telescope near-infrared camera and multiobject spectrometer (NICMOS) images in the F110W (J110) and F160W (H160) filters. VLA J123642+621331 has a single emission line at 6595 Å, which we identify with Lyalpha at z=4.424. We argue that this faint (H160=23.9 mag), compact (re approximately 0&farcs;2), red (I814-K=2.0) object is most likely a dusty, star-forming galaxy with an embedded active nucleus.

Journal Article↗
PubMed2000

Development of Coronal Mass Ejections: Radio Shock Signatures.

We present observational imaging evidence for the existence of metric radio bursts closely associated with the front edge of coronal mass ejections (CMEs). These radio bursts drift in frequency similarly to type II bursts. They are weak and usually go undetected on spectrograph data. We find the same measured projected velocity for the displacement of, respectively, the radio source (when observed at two or more frequencies) and the CME leading edge. The position of the emitting source coincides with the CME leading edge. Among the events analyzed, the fastest of them, with a velocity over 1400 km s-1, was associated with interplanetary type II bursts.

Journal Article↗
PubMed2000

Chandra X-Ray Detection of the Radio Hot Spots of 3C 295.

An observation of the radio galaxy 3C 295 during the calibration phase of the Chandra X-Ray Observatory reveals X-ray emission from the core of the galaxy, from each of the two prominent radio hot spots, and from the previously known cluster gas. We discuss the possible emission processes for the hot spots and argue that a synchrotron self-Compton (SSC) model is preferred for most or all of the observed X-ray emission. SSC models with near-equipartition fields thus explain the X-ray emission from the hot spots in the two highest surface brightness FR II radio galaxies, Cygnus A and 3C 295. This lends weight to the assumption of equipartition and suggests that relativistic protons do not dominate the particle energy density.

Journal Article↗
PubMed2000

Radio Detection of a Rapid Disturbance Launched by a Solar Flare.

We report the direct observation of motion associated with a solar flare at a speed of 26,000 km s-1. The motion is seen from a radio source at 0.33 GHz, which suddenly starts moving during the flare. At its peak, the radio source covers a quiet region of dimension 500&arcsec;. Emission from any given location is sporadic. The disturbance itself does not seem to radiate, but it excites coronal features that continue to radiate after it passes. The inferred velocity is larger than any previously inferred velocity of a disturbance in the solar atmosphere apart from freely streaming beams of accelerated electrons. The observed motion of the source at a fixed frequency, low polarization, and moderate bandwidth are more consistent with the typical properties of moving type IV radio bursts than with classical coronal shock-associated type II bursts, but any disturbance at such a high velocity must be highly supersonic and should drive a shock. We speculate that the disturbance is associated with the realignment of magnetic fields connecting different portions of an active region.

Journal Article↗
PubMed2003

Interferons can upregulate the expression of the tumor associated antigen G250-MN/CA IX, a potential target for (radio)immunotherapy of renal cell carcinoma.

BACKGROUND: Interleukin-2 (IL-2) and interferon-alpha (IFN-alpha) can induce therapeutic responses in a minority (5-25%) of patients with metastatic renal cell carcinoma (RCC). G250-MN/CA IX, a tumor-associated antigen expressed on the majority of clear cell RCCs, is a potential (radio)immunotherapeutic target for G250-antibody based (radio)immunotherapy. We investigated the effect of the biological response modifiers (BRMs) IL-2, IFN-alpha, and IFN-gamma on the expression of the G250 antigen on RCC cells. METHODS: In vitro, the expression of the G250 antigen was measured by flow cytometry (FCM) after culturing RCC cells in the presence of various concentrations of the BRMs. Additionally, the number of G250 epitopes per cell was determined quantitatively by Scatchard analysis. RESULTS: Upregulation of G250 expression was observed on RCC cells cultured in the presence of IFN-alpha or IFN-gamma, whereas the addition of IL-2 had no effect. For both IFNs a clear dose-response relation between G250 antigen expression and IFN dose was observed, with IFN-gamma being the more potent agent. G250 expression could be upregulated four-fold. Interestingly, the effect of combining IFN-alpha and IFN-gamma revealed a more pronounced upregulation of G250 expression than either one of the IFNs alone. CONCLUSIONS: On the basis of in vitro experiments, G250 expression can be upregulated by IFN-alpha and IFN-gamma. In vivo studies are warranted to investigate whether due to IFN treatment increased G250 expression occurs, and whether increased G250 expression can enhance the therapeutic efficacy of G250-antibody based (radio)immunotherapy.

Antibodies, Monoclonal↗