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Biomedical subjects

H A Levy

Publications and source records attributed to H A Levy.

18 recordsLinked to original sources
PubMed1994

Modeling the 3-D RNA distribution in the Balbiani ring granule.

Mature Balbiani Ring (BR) granules in situ were stained with the nucleic acid specific stain, osmium ammine-B, recorded by electron spectroscopic imaging and reconstructed by electron microscope tomography to examine the three-dimensional (3-D) distribution of BR heterogeneous nuclear RNA (hnRNA). The BR2 granules contain ca. 37 kb of mRNA. Reconstructed BR granules were selected to emphasize one of the prevalent conformations seen in the sectioned salivary glands, the en face or "pin-wheel" conformation. A variety of image processing and volume-rendering operations were applied to the set of reconstructed BR granules. Some of the conclusions of this study are the following: (1) RNA distribution is not uniform throughout the granule; (2) RNA is condensed into about ten particles per granule, which all appear to possess approximately the same RNA stain density; (3) heterogeneity exists in the positions and sizes of particles within the various BR granules. These data argue for the folding of a beaded ribbon, consisting of connected particulate condensations of BR mRNA, possessing considerable 3-D flexibility, even in the packaged state. A comparison of this beaded-ribbon model and a prior folded hnRNP fiber model is also presented.

Animals↗
PubMed1993

Electron microscope tomography of Balbiani Ring hnRNP substructure.

Three-dimensional (3-D) reconstructions, by electron microscope tomography, of selectively stained, contrast enhanced Balbiani Ring (BR) hnRNP granules reveal a complex spatial arrangement of RNA-rich domains. This particulate substructure was examined by volume rendering computer graphics. Modeling the arrangement of RNA-rich domains is made difficult by apparent structural flexibility and/or heterogeneity of composition. Formulation of a consensus 3-D arrangement of RNA-rich domains will require an expanded data base of reconstructed BR granules and the development of new image manipulation and analysis techniques. This study demonstrates the potential for ultrastructural cell biology of combining several new techniques: selective nucleic acid staining, electron spectroscopic imaging to enhance contrast, electron microscope tomography and volume rendering computer graphics.

Animals↗
PubMed1989

Tomographic reconstruction from energy-filtered images of thick biological sections.

Energy filtration makes it possible to image an approximately 0.5 microm biological section at 80 kV in the electron microscope. Based on spectra taken at different tilt angles, we chose the most probable energy loss, deltaEp +/- 10eV for each tilt angle, as the imaging energy window. A complete tilt series from +60 degrees to -60 degrees at 2.5 degree intervals was collected on the Zeiss EM902 and used in a tomographic reconstruction of transcriptionally active chromatin in the Balbiani ring of Chironomus tentans.

Animals↗
PubMed1987

Effect of reserpine on salivary gland radioiodine uptake in thyroid cancer.

Nine patients with thyroid cancer were treated with reserpine in an attempt to reduce radiation exposure to the salivary glands from 100-150 mCi doses of I-131 therapy to thyroid remnants or metastases. Three control patients were not treated with reserpine but did receive 100-150 mCi of I-131. Parotid/background ratios of activity after radioablative doses of I-131 in patients not treated with reserpine were significantly higher than the patients treated with reserpine, and this was also true seven days after the radioablative dose. Combined therapy with reserpine, chewing gum, lemon candies, and hydration is suggested for the prevention of sialadenitis and xerostomia due to large doses of radioiodine.

Adenocarcinoma↗
PubMed1987

The varifocal mirror for 3-D display of electron microscope tomography.

Three-dimensional reconstruction by tomographic procedures of objects viewed with transmission electron microscopy generates a volume of densities arrayed in raster format. This volume can be conveniently displayed and analysed employing a varifocal mirror (VFM) and an associated image processing system. We have developed a number of interactive programs useful to display and analyse the 3-D data, including depth windowing, intensity mapping, image zoom, image rotation and cursor overlay. Examples of these functions are presented, employing data from electron microscope tomography (EMT) of a transcriptionally-active eukaryotic gene, the Balbiani ring of Chironomus polytene chromosomes.

Animals↗
PubMed1987

Unilateral thoracic soft-tissue accumulation of bone agent in lung cancer.

One hundred thirty patients with lung cancer were studied to determine the incidence of unilateral thoracic soft-tissue accumulation (UTS) of 99mTc methylene diphosphonate (MDP). The finding was present in 60 of 130 (46%) of the patients. Of 52 patients who had received radiation therapy to the primary tumor in the chest, 46 (88%) had UTS, while six (12%) did not. Radiation therapy to lung tumors was the most significant of the factors studied in unilateral soft-tissue uptake of bone agent in the thorax of patients with lung cancer.

Aged↗
PubMed1986

DNA compaction during intense transcription measured by electron microscope tomography.

Thick sections (0.5-1.0 micron) containing pilocarpine-hyperstimulated Balbiani ring (BR) genes of Chironomus tentans salivary glands were reconstructed by electron microscope tomography (EMT). Six transcription loops were analyzed at low resolution permitting a measurement of transcription unit length in situ. Comparison of the average transcription unit length with the BR gene coding region DNA length yields an estimate of the DNA compaction ratio in situ. The estimated DNA compaction ratio (approximately 3-fold) is consistent with a significant degree of nucleosome unfolding in the hyperstimulated BR genes.

Chironomidae↗
PubMed1985

The use of scintigraphic studies in mid-ventricular obstructive cardiomyopathy to rule out pseudoaneurysm.

A "pseudo-pseudo" aneurysm of the left ventricle due to mid-ventricular obstruction from asymmetric septal hypertrophy is presented. A case of mid-ventricular hypertrophic obstructive cardiomyopathy (MVHOCM) was evaluated by means of echocardiography, angiocardiography, gated cardiac blood pool scanning, and a TI-201 myocardial scan. The gated cardiac blood pool scan appearance of MVHOCM is similar to pseudoaneurysm of the left ventricle. TI-201 myocardial imaging, however, was able to distinguish between MVHOCM and pseudoaneurysm of the left ventricle.

Aged↗
PubMed1984

Modeling Balbiani Ring gene transcription with electron microscope tomography.

Cross-sectional views of mature regions of Balbiani Ring (BR) transcription loops were reconstructed by electron microscope tomography. Balsa wood models were built based upon the resulting tomograms. Coordinates of the centers of the ribonucleoprotein BR granules were estimated and employed to calculate the approximate orientation of the BR transcription unit axis in the plastic section. The density of BR granules per micron of transcription unit axis was estimated. Employing structural parameters for mature regions of BR transcription loops derived from present and previous studies, theoretical calculations were performed to examine potential steric restrictions around the central chromatin axis. Tomograms were also observed and photographed on a varifocal (vibrating) mirror to illustrate the utility of a rapid user-interactive 3-D display.

Animals↗
PubMed1983

Electron microscope tomography: transcription in three dimensions.

Three-dimensional reconstruction of an asymmetric biological ultrastructure has been achieved by tomographic analysis of electron micrographs of sections tilted on a goniometer specimen stage. Aligned micrographs could be displayed as red-green three-dimensional movies. The techniques have been applied to portions of in situ transcription units of a Balbiani ring in the polytene chromosomes of the midge Chironomus tentans. Current data suggest a DNA compaction of about 8 to 1 in a transcription unit. Nascent ribonucleoprotein granules display an imperfect sixfold helical arrangement around the chromatin axis.

Animals↗
PubMed1983

Splenic avulsion and bleeding shown on radiocolloid images.

A case is discussed of a man who presented with trauma to the chest and abdomen. A radiocolloid image showed uptake by the liver. However, the spleen was not identified. Areas of activity outside of the spleen were noted. The patient had splenic avulsion; extra sites of activity likely represented bleeding sites in the abdomen. Failure to identify the spleen on a radiocolloid image, after trauma, should be an alerting sign to possible splenic avulsion (especially when there are also ectopic sites of accumulation of the radiocolloid).

Hemorrhage↗
PubMed1982

Incidence of a pyramidal lobe on thyroid scans.

Gamma camera pertechnetate and radioiodine thyroid scans were reviewed to determine the incidence of recognition of a pyramidal lobe. Ten to 17% of "normals" and of patients with various thyroid disease states had a pyramidal lobe on their scans. However, in patients with diffuse toxic goiter, 43% had a pyramidal lobe on the thyroid images. There appears to be a correlation between elevated thyroid function studies (likely in thyroid mass) and the incidence of a pyramidal lobe on thyroid scans in diffuse toxic goiter.

Female↗