Divalent cation distribution in dinoflagellate chromosomes imaged by high-resolution ion probe mass spectrometry.

From a variety of analytical electron microscopy experiments, the chromosomes of dinoflagellates are known to contain sizeable amounts of cations, the latter thought to contribute to the neutralization of the negative charge carried by the phosphate groups in the DNA backbone. From previous Ca and Mg chelation experiments, it is also known that these cations are necessary for the compaction and preservation of the chromosome architecture. Similar conclusions have been recently presented by our group concerning mammalian mitotic chromosomes, in studies based on secondary ion mass spectrometry (SIMS) carried out with the University of Chicago high-resolution scanning ion microprobe (UC-SIM).

The eyes of trilobites: The oldest preserved visual system.

The oldest preserved visual systems are to be found in the extinct trilobites, marine euarthropods which existed between about 520 and 250 million years ago. Because they possessed a calcified cuticle, they have a good fossil record, and commonly the lens-bearing surfaces of their paired compound eyes are well preserved. The sublensar structures, however, remain unknown.

Chronic acidosis-induced alteration in bone bicarbonate and phosphate.

Chronic metabolic acidosis increases urinary calcium excretion without altering intestinal calcium absorption, suggesting that bone mineral is the source of the additional urinary calcium. In vivo and in vitro studies have shown that metabolic acidosis causes a loss of mineral calcium while buffering the additional hydrogen ions. Previously, we studied changes in femoral, midcortical ion concentrations after 7 days of in vivo metabolic acidosis induced by oral ammonium chloride.

Acute acidosis-induced alteration in bone bicarbonate and phosphate.

During an acute fall in systemic pH due to a decrease in the concentration of serum bicarbonate ([HCO(3)(-)]), metabolic acidosis, there is an influx of hydrogen ions into the mineral phase of bone, buffering the decrement in pH. When bone is cultured in medium modeling acute metabolic acidosis, the influx of hydrogen ions is coupled to an efflux of sodium and potassium and a depletion of mineral carbonate. These ionic fluxes would be expected to neutralize some of the excess hydrogen ions and restore the pH toward normal.

Cation-chromatin binding as shown by ion microscopy is essential for the structural integrity of chromosomes.

Mammalian interphase and mitotic cells were analyzed for their cation composition using a three-dimensional high resolution scanning ion microprobe. This instrument maps the distribution of bound and unbound cations by secondary ion mass spectrometry (SIMS). SIMS analysis of cryofractured interphase and mitotic cells revealed a cell cycle dynamics of Ca2+, Mg2+, Na+, and K+.

Contribution of organic material to the ion composition of bone.

Studies of bone mineral ranging from cadaveric analysis to the use of high-resolution ion microprobe with secondary ion mass spectroscopy (SIMS) have concluded that bone is rich in sodium and potassium relative to calcium. Exposure of bone to acid conditions either in vitro or in vivo leads to an exchange of hydrogen ions for sodium and potassium buffering the acidity of the medium or blood, respectively. Whether these monovalent ions reside within the mineral or organic phases of bone has never been determined.

Effects of in vivo metabolic acidosis on midcortical bone ion composition.

Chronic metabolic acidosis increases urine calcium excretion without altering intestinal calcium absorption, suggesting that bone mineral is the source of the additional urinary calcium. During metabolic acidosis there appears to be an influx of protons into bone mineral, lessening the magnitude of the decrement in pH. Although in vitro studies strongly support a marked effect of metabolic acidosis on the ion composition of bone, there are few in vivo observations.

A secondary ion mass spectroscopic study of the elemental composition pattern in rat incisor dental enamel during different stages of ameloblast differentiation.

In most earlier studies on the elemental composition pattern of dental enamel, a picture is presented which describes a limited region. In this study, estimates of the incorporation of some critical elements into enamel were correlated with the differentiation stages of the ameloblasts through out the whole tooth. Elemental analyses of rat incisor dental enamel during the secretory, transitional and maturation phases were performed using two different modes of secondary ion mass spectrometry (SIMS).

Effect of metabolic acidosis on the potassium content of bone.

Metabolic acidosis induces resorption of cultured bone, resulting in a net efflux of calcium (Ca) from the bone and an apparent loss of mineral potassium (K). However, in these organ cultures, there is diffusion of K between the medium and the crystal lattice, causing difficulty in interpretation of the acid-induced changes in mineral ion composition. To determine the effects of acidosis on bone mineral K, we injected 4-day-old neonatal mice with pure stable isotope 41K, equal to approximately 5% of their total body K.

Imaging of BrdU-labeled human metaphase chromosomes with a high resolution scanning ion microprobe.

Detailed maps of the A-T distribution within human mitotic chromosomes labeled with BrdU are obtained with a high resolution scanning ion microprobe through the detection of bromine by imaging secondary ion mass spectrometry (SIMS). Corresponding maps of the emission loci of the molecular ion CN- describe the overall DNA, RNA and protein distribution in the chromosomes. Several chromosome preparations exhibit base-specific banding patterns (SIMS-bands) which mimic the well known G- or Q-bands resulting from conventional staining methods for optical microscopy.

Effects of osteoclastic resorption on bone surface ion composition.

Osteoclasts are responsible for resorption of bone mineral. To determine how osteoclasts alter bone surface ion composition, neonatal mouse bone cells were isolated and cultured in the presence of parathyroid hormone (PTH) on bovine cortical bone. Surface ion composition of the resulting osteoclastic resorption pits was compared with that of unresorbed bone, utilizing a high-resolution scanning ion microprobe.

Advances in high resolution SIMS studies of BrdU-labelled human metaphase chromosomes.

The detection of bromine in human metaphase chromosomes labelled with the thymidine-analog BrdU, by imaging Secondary Ion Mass Spectrometry (SIMS) with a high resolution scanning ion microprobe, provides detailed maps of the AT distribution within the chromosomes. Similarly, maps of the emitted CN-molecular ions describe the overall DNA, RNA and protein distribution, details of which are also revealed by maps of the divalent cations Ca+ and Mg+. Base-specific banding patterns (SIMS bands), mimicking the well known G-or Q-bands resulting from conventional staining methods for optical microscopy, are observed in several preparations, more noticeably in mitotic cells at the first cell division, after in situ DNA denaturation, or Giemsa staining.

Effects of aluminum on bone surface ion composition.

Aluminum induces net calcium efflux from cultured bone. To determine whether aluminum alters the bone surface ion composition in a manner consistent with predominantly cell-mediated resorption, a combination of cell-mediated resorption and physicochemical dissolution or physicochemical dissolution alone, we utilized an analytic high-resolution scanning ion microprobe with secondary ion mass spectroscopy to determine the effects of aluminum on bone surface ion composition. We cultured neonatal mouse calvariae with or without aluminum (10(-7) M) for 24 h and determined the relative ion concentrations of 23Na, 27Al, 39K, and 40Ca on the bone surface and eroded subsurface.

Nucleotide and protein distribution in BrdU-labelled polytene chromosomes revealed by ion probe mass spectrometry.

Detailed chemical maps of BrdU-labelled polytene chromosomes of Drosophila melanogaster, obtained by imaging secondary ion mass spectrometry, reveal separately the distribution of DNA and proteins in the chromosomes. The thymidine-analogue BrdU within the chromosomal DNA is localized by detecting the Br- secondary ion signal, while both nucleic acid and protein content are mapped through the abundantly emitted CN- signal. This novel approach supercedes, and helps explain the origin of, the banding patterns that are observed by conventional staining techniques.

The use of the stable isotope 44Ca in studies of calcium incorporation into dentin.

The incorporation into rat incisor dentin of two calcium isotopes, the stable 44Ca and the radioactive 45Ca, was studied using secondary ion mass spectrometry (SIMS) step-scanning and imaging, and autoradiography, respectively. The results demonstrated a time-dependent incorporation of the calcium isotopes into the mineral phase of dentin. With the SIMS step-scanning, detecting 44Ca, the ion yield was high in the odontoblasts 2 min after intravenous injection.

The absence of correlations between a clinical classification and ultrastructural findings in amelogenesis imperfecta.

This study was performed to examine whether a clinical classification of different phenotypes of amelogenesis imperfecta could be discernible at the ultrastructural level. Seventeen primary teeth from 16 children with hypomineralization, hypomaturation, or hypoplastic variants of the disease were collected for histologic studies of the enamel by means of polarized light microscopy, scanning electron microscopy (SEM), and secondary ion mass spectrometry (SIMS). Polarization microscopy showed that the enamel was hypomineralized; in six teeth a wavy configuration of the enamel prisms also appeared.

Physicochemical effects of acidosis on bone calcium flux and surface ion composition.

Net calcium flux (JCa) from bone in vitro is pH dependent. When pH falls below 7.40, through a reduction in [HCO3-], there is both physicochemical and cell-mediated JCa.

Cytogenetic applications of high resolution secondary ion imaging microanalysis: detection and mapping of tracer isotopes in human chromosomes.

Analytical imaging by secondary ion mass spectrometry (SIMS) using a state-of-the-art scanning ion microprobe enables the detection and mapping of tracer isotopes in human metaphase chromosomes. The stimulated mitosis of cells cultured in media containing labelled nucleosides, typically 14C-labelled thymidine or adenosine, and BrDU, yields chromosomes that have incorporated the labelled molecule in their constituent DNA. The label is subsequently detected and localized by SIMS imaging.

Alteration in surface ion composition of cultured bone during metabolic, but not respiratory, acidosis.

Acidosis produced by a fall in [HCO3-] (metabolic acidosis, Met) produces greater Ca efflux from cultured bone than that produced by a rise in PCO2 (respiratory acidosis, Resp). To compare the effects of Met and Resp on bone surface ion composition we measured the surface abundance of 40Ca, 23Na, and 39K in cultured bone with a scanning ion microprobe utilizing secondary-ion mass spectrometry. Neonatal mouse calvariae were incubated for 24 h in medium simulating either Met (pH = 7.

Comparison of in vitro and in vivo 44Ca labeling of bone by scanning ion microprobe.

To determine whether Ca incorporation from medium into cultured bone represents normal mineralization, we labeled some neonatal mouse calvariae in vitro and others in vivo with the stable isotope 44Ca and compared surface label localization with a scanning ion microprobe utilizing secondary ion mass spectrometry. To label in vitro, we incubated live calvariae in medium containing 40Ca or 44Ca for 3 h. Compared with a 44Ca/40Ca ratio of 0.

Scanning ion microprobe assessment of biological sample preparation techniques.

Different preparation techniques for high lateral resolution scanning ion microprobe imaging of biological samples have been investigated. The sharpest histological maps are obtained from chemically fixed and plastic embedded specimens. It is often problematic to correlate ultrastructure and bioaccumulation from analysis of frozen cut and lyophilized sections.

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.

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.

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).