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Biomedical subjects

R Levi-Setti

Publications and source records attributed to R Levi-Setti.

At least 37 records · Page 2Linked to original sources
PubMed1989

Ion microprobe analysis of mouse calvariae in vitro: evidence for a "bone membrane".

It is not clear whether the bone mineral is in passive physicochemical equilibrium with the extracellular fluid (ECF) or is separated from it by a metabolically active partition, a so-called "bone membrane." We used a sensitive high spatial resolution scanning ion microprobe utilizing secondary ion mass spectrometry to compare the relative concentrations of 23Na, 39K, and 40Ca on the surface, subsurface, and cross section of cultured live bone with the concentrations in similar regions of dead bone. Calvariae from neonatal mice were dissected and either incubated for 24 h (live) or subjected to 3 freeze-thaw cycles to kill the bone cells prior to incubation (dead). The live bone has abundant surface Na and K relative to Ca and the Na/K is approximately unity. With dead bone there is a dramatic fall in the K/Ca and an increase in the Na/K. These findings are most consistent with an egress of bone K after cell death. Flux measurements indicate a net influx of Ca into the dead bone. The marked change in relative ion concentrations with cell death indicates that live bone is not in passive physiochemical equilibrium with the surrounding medium. There appears to be a metabolically active partition, a so-called bone membrane, between the mineral and the culture medium that utilizes bone cells to maintain ion gradients.

Animals↗
PubMed1989

Ion microprobe analysis of bone surface elements: effects of 1,25(OH)2D3.

When neonatal mouse calvariae are incubated with 1,25-dihydroxyvitamin D3 [1,25(OH)2D3] there is net calcium efflux from the bone into the medium. The effect of this enhanced cell-mediated Ca efflux on the relative concentrations of mineral 23Na, 39K, and 40Ca has not previously been studied. We used an imaging scanning ion microprobe, utilizing secondary ion mass spectrometry, to compare the relative ion concentrations of Na, K, and Ca on the surface, subsurface, and cross-section of cultured bone incubated in the presence of 1,25(OH)2D3 with the ion concentrations in similar regions of bone incubated in unaltered control medium. Changes in mineral ion concentration were correlated with net fluxes of Na, K, and Ca relative to bone. Calvariae incubated in control medium (24 h at pH approximately 7.40) have abundant surface Na and K relative to Ca (Na/Ca, 85 and K/Ca, 68), whereas the subsurface has less Na/Ca (21) and K/Ca (23), and on cross section the ratios of both Na/Ca (2.0) and K/Ca (1.9) decrease further. After incubation with 10(-8) M 1,25(OH)2D3, there is a significant increase in bone surface Na/Ca (154) and K/Ca (141) without a change in these ratios on the subsurface and a small fall in both ratios on cross section. The linear relationship between Na/Ca and K/Ca across the three regions of bone observed in control calvariae did not change with 1,25(OH)2D3 treatment. As determined by flux measurements there is a net efflux of Ca but not Na or K from bone.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Trifluorothymidine localization in the rabbit cornea by secondary ion mass spectrometry imaging microanalysis.

Imaging microanalysis by secondary ion mass spectrometry is a sensitive surface analytical technique that allows the detection and localization of elements and compounds in biological tissues. We report the detection by this approach of intracorneal trifluorothymidine following topical administration in rabbit with normal cornea. The presence of trifluorothymidine is revealed using 19F as a marker, allowing the acquisition of ultrastructural microanalytical images without using radioactive tracers.

Animals↗
PubMed1989

Cytochemical study of abnormal intranuclear structures rich in beryllium.

During prolonged intoxication with beryllium sulphate, intranuclear beryllium-rich structures (IBRS) develop mainly in the cells of the convoluted tubules of the kidney. These structures are constituted by the accumulation of dense granules approximately 20 nm in diameter. The present work shows: 1) by electron probe microanalysis that IBRS are rich in phosphorus and calcium, and 2) by high resolution ion microanalysis that the granules are rich in beryllium and proteins. Staining with thallium alcoholate and regressive staining with ethylenediaminetetraacetate (EDTA) seem to demonstrate the presence of ribonucleoproteins in the granules. But the richness in calcium and phosphorus makes it difficult to interprete cytochemical reactions based on thallium and lead because complexes can be formed between calcium and thallium or lead, and between phosphorus and lead. Extraction with EDTA and digestion with RNase carried out on floating slices fixed with glutaraldehyde and embedded in glycol methacrylate show that: 1) the positive response of IBRS to cytochemical techniques used seems due solely to calcium; 2) the RNase forms a stable complex with a constituent of the granules that could be the highly phosphorylated acidic protein that binds preferentially to beryllium described by Parker and Stevens.

Animals↗
PubMed1988

Selective intracellular beryllium localization in rat tissue by mass-resolved ion microprobe imaging.

Beryllium absorption sites in the kidney and liver of rats have been located and imaged at approximately 70 nm lateral resolution with a scanning ion microprobe utilizing secondary ion mass spectrometry. Embedded sections and lyophilized cryosections of these organs were prepared after in vivo administration of beryllium in soluble form. Beryllium distribution images were correlated with the histological microstructure revealed by CN- images. In the kidney, beryllium concentrates selectively within the nuclei of proximal tubule cells and occasionally within modified podocytes or mesangial cells in the glomerulus. In the liver, beryllium is seen to localize within severely altered lysosomal structures as well as within hepatocyte nuclei. These observations are relevant to understanding aspects of the toxic and carcinogenic properties of absorbed beryllium compounds.

Animals↗
PubMed1988

Elemental imaging of dental hard tissues by secondary ion mass spectrometry.

High resolution imaging by secondary ion mass spectrometry (SIMS) has been employed in a chemical-microstructural pilot study of different classes of hard tissues from human and rat. The special scanning ion microprobe instrumentation permitted the recording of element-resolved images with a lateral resolution of about 50 nm. Sharp distribution micrographs were obtained for Ca+, F- and CN-, and in selected specimens for Na+, K+, Mg+, O-, Cl-, C- and PO-. Several trends in the elemental kinetics of mineralization were comprehensively illustrated and new aspects were indicated. The paper points out the broad scope of interest, and the potentialities of unique applications, in SIMS imaging of biomineralized tissues, the conditions for efficient employment of the recently developed technique are briefly discussed and demonstrated.

Animals↗
PubMed1988

Ion microscopy: a new approach for subcellular localization of labelled molecules.

Secondary ion mass spectroscopy (SIMS) was used to obtain images representing the intracellular distribution of molecules labelled with carbon 14. Deoxyadenosine labelled with carbon 14 was added to a cultured human fibroblast cell medium, and the intracellular distribution of this molecule was studied using three different SIMS instruments: the CAMECA IMS 3F and SMI 300 ion microscopes and the UC-HRL scanning ion microprobe. Carbon 14 distribution images obtained by this method show that deoxyadenosine U-C14 is present in the cytoplasm as well as the nucleus, with a higher concentration in the nucleoli. Our study clearly demonstrates that ion microscopy is well suited for carbon 14 detection and localization at the subcellular level, permitting a wide variety of microanalytical tracer experiments.

Adult↗
PubMed1986

Ion microprobe determination of bone surface elements: effects of reduced medium pH.

When neonatal mouse calvariae are cultured in a medium having a low pH they release calcium (Ca) while buffering protons (H). However, for 1 neq Ca released, 16-21 neq H enter the calvariae, arguing strongly against simple dissolution of bone mineral as the mechanism of H buffering. To determine if H for sodium (Na) exchange could explain the lack of stoichiometry between H and Ca, we cultured calvariae for 3 h in control (pH = 7.40 +/- 0.01) or reduced-pH (pH = 7.21 +/- 0.01) medium and then examined the surface Na, K, and Ca using a high-resolution scanning ion microprobe. The calvarial surface was rich in Na and K relative to Ca (Na/Ca, 52 +/- 17; K/Ca, 61 +/- 17; all values are the ratios of counts per second of detected secondary ions, means +/- SE). Compared with the surface the calvarial cross section contained far less Na and K relative to Ca (Na/Ca, 2 +/- 1; K/Ca, 1 +/- 1; both P less than 0.01 vs. surface). Compared with the control surface, culture in a reduced-pH medium reduced the surface Na and K relative to Ca (Na/Ca, 5 +/- 1; K/Ca, 7 +/- 1; both P less than 0.025 vs. surface) to values still greater than the cross section (P less than 0.05 for both). Neonatal mouse calvariae have a surface that is rich in Na and K relative to Ca. Reduced medium pH depletes surface Na and K of cultured calvariae with respect to Ca.

Acidosis↗
PubMed1985

Progress in high resolution scanning ion microscopy and secondary ion mass spectrometry imaging microanalysis.

The performance of a new high resolution scanning ion microprobe (SIM) is elucidated with regard to imaging capabilities using the ion-induced secondary electron (ISE) or secondary ion (ISI) signals, and the mass-resolved signal from a secondary ion mass spectrometry (SIMS) system. The new instrument focuses a beam extracted from a liquid metal ion source (LMIS) to a range of spot sizes reaching the 20 nm level. The probe current (1.6 pA) available at this level of lateral resolution, which approaches the theoretical resolution limits of the SIMS method, is still adequate to obtain detailed isotopic maps for surfaces rich in the elements of low ionization potential (positive ISI), or high electron affinity (negative ISI). In addition to examples of high resolution ISE and ISI images of objects displaying sufficiently small topographic detail, mass spectra and isotopic maps are shown, testing both the lateral and depth resolution attained. The latter results belong with a program of interdisciplinary research applications of the new microprobe, which include studies of e.g., the monolayer lateral distribution of intercalant in SbCl5 intercalated graphite and of silicate minerals and iron distribution in sections of chondrules and their rims (components of chondrites, a class of stony meteorites). In the biomedical field, the new microprobe finds application in e.g., the study of human renal calculi and bone. Most promising is the use of stable isotope tracers (e.g., Ca44) to unravel the dynamics of bone mineralization, as thus far shown with the in-vitro culture of the skull bone of neonatal mice.

Animals↗
PubMed1979

A new eye shield based on an optimized pinhole array.

The new eye shield described here incorporates the principles of a compound array that provides a significant improvement in vision (from hand movements to 20/100 or better) in a nonaccommodative eye, while retaining all other properties (protection, ventilation, reduction of glare) of eye shields used currently. It is recommended for routine use in patients after intraocular surgery and pupillary dilatation.

Eye Protective Devices↗
PubMed1975

Trilobite eyes and the optics of Des Cartes and Huygens.

The thick lenses in the aggregate eyes of a group of trilobites were double structures designed to eliminate spherical aberration. The shape of the optically correcting interface is in accord with constructions by Des Cartes and Huygens and is dictated by a fundamental law of physics. Trilobites may have evolved such sophisticated eye-lenses to maximise optic neurone response in a dimly lit environment.

Adaptation, Physiological↗
PubMed1975

Scanning transmission ion microscope with a field ion source.

Experiments with a low-resolution scanning transmission ion microscope, using hydrogen ions from a field ionization source, indicate that it will be feasible by this approach to aim at high-resolution ion microscopy. Micrographs of unstained biological specimens have been obtained by critical range absorption of a 55 keV hydrogen ion beam at a resolution of 2000 A.

Animals↗