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PubMed1989

Quantitative morphology of the zinc-iodide-osmium (ZIO) stained synaptic vesicles.

A computer assisted morphometric method has been elaborated to quantify synaptic vesicles evidenced by means of the Zinc-Iodide-Osmium (ZIO) staining procedure in nerve endings of a very discrete area of the cerebellar granular layer: the glomerulus. The following parameters were calculated directly on electron microscopic negatives of 4.67 microns 2 of surface terminal area: number of vesicles per unit area (Na), and per unit volume (Nv), volume density (Vv), average diameter (d) and average volume of the single vesicle (V). Ultrastructural changes taking place at nerve endings also cover synaptic vesicles, thus quantitative studies regarding vesicle population at synaptic regions can be correlated to functional changes occurring in the process of chemical transmission and reflect the plasticity of synaptic junctional zones. Although this histochemical staining method generally is referred to as unspecific, after comparing our data with the available literature reports, we propose that ZIO-positive vesicles could have a physiological significance. These ZIO-positive organelles could take part in the intraterminal homeostatic control of Ca++ ions.

Animals↗
PubMed1989

[Dental findings in a case of idiopathic hypoparathyroidism].

Idiopathic hypoparathyroidism is characterized by a deficiency of the parathyroid hormone, origin unknown, and causes a low serum calcium and a high serum inorganic phosphorus. This report concerns a clinical observation of a case of idiopathic hypoparathyroidism. This case was examined from the dental point of view. The findings were as follows: 1. The roentgenographic findings revealed that there was no demonstrable abnormality concerning bone age indicated between the ages of 5 and 6 years. 2. Severe dental caries were noted in the deciduous teeth and the permanent teeth. 3. Hypoplasia and hypocalcemia were recognized in most of the permanent teeth. 4. Large pulp chambers were observed in the deciduous teeth and the permanent teeth, and thickening of the lamina dura was observed in the permanent teeth. 5. The histological findings of the extracted deciduous teeth and the upper right first molar were such that: (1) there was hypoplasia and hypocalcemia in the dentin of deciduous teeth, and there were multiple resorptions in the cementum. (2) there was hypoplasia in the enamel of the upper right first molar. 6. Electron probe microanalysis of the upper left second molar revealed that the degree of mineralization and concentration of Ca, P and Mg in the dentin of the root showed a lower intensity than in the dentin of the normal one. 7. It was assumed from the dental point of view that this hypoparathyroid condition first appeared at about 11'months approximately 18'months of age.

Child, Preschool↗
PubMed1989

Bonding behavior of a glass-ceramic containing apatite and wollastonite in segmental replacement of the rabbit tibia under load-bearing conditions.

Glass-ceramic implants containing apatite and wollastonite were studied under load-bearing conditions in a segmental replacement model in the tibia of the rabbit. Alumina-ceramic implants were used as a control. A sixteen-millimeter segment of the middle of the shaft of the tibia was resected at a point distal to the junction of the tibia and the fibula. The defect was replaced by a fifteen-millimeter-long hollow, cylindrical implant that was fixed by intramedullary nailing using a Kirschner wire. Two groups of eight rabbits each (one group with a glass-ceramic implant and the other with an alumina implant) were killed twelve weeks after implantation. Two similar groups were killed twenty-five weeks after implantation. The segment of the tibia that contained the implant was excised and tension-tested. The load to failure of glass-ceramic implants containing apatite and wollastonite increased with time. The loads to failure of the glass-ceramic and alumina implants at twelve weeks after implantation were 19.8 +/- 7.06 and zero newtons, respectively. The loads to failure of glass-ceramic and alumina implants at twenty-five weeks after implantation were 126.4 +/- 32.54 and 19.6 +/- 13.92 newtons, respectively. No glass-ceramic implants broke. A calcium-phosphorus layer at the interface of the glass-ceramic and the bone was observed by scanning electron microscopy and electron-probe microanalysis. There was no interposition of soft tissue between the glass-ceramic and the bone, as observed by Giemsa surface staining.

Aluminum Oxide↗
PubMed1985

Fe(III).ATP complexes. Models for ferritin and other polynuclear iron complexes with phosphate.

Polynuclear iron complexes of Fe(III) and phosphate occur in seawater and soils and in cells where the iron core of ferritin, the iron storage protein, contains up to 4500 Fe atoms in a complex with an average composition of (FeO.OH)8FeO.OPO3H2. Although phosphate influences the size of the ferritin core and thus the availability of stored iron, little is known about the nature of the Fe(III)-phosphate interaction. In the present study, Fe-phosphate interactions were analyzed in stable complexes of Fe(III).ATP which, in the polynuclear iron form, had phosphate at interior sites. Such Fe(III).ATP complexes are important not only as models but also because they may play a role in intracellular iron transport and in iron toxicity; the complexes were studied by extended x-ray absorption fine structure, EPR, NMR spectroscopy, and measurement of proton release. Mononuclear iron complexes exhibiting a g' = 4.3 EPR signal were formed at Fe:ATP ratios less than or equal to 1:3, and polynuclear iron complexes (Fe greater than or equal to 250, EPR silent at g' = 4.3) were formed at an Fe:ATP ratio of 4:1. No NMR signals due to ATP were observed when Fe was in excess (Fe:ATP = 4:1). Extended x-ray absorption fine structure analysis of the polynuclear Fe(III).ATP complex was able to distinguish an Fe-P distance at 3.27 A in addition to the octahedral O at 1.95 A and 4-5 Fe atoms at 3.36 A. The Fe-O and Fe-Fe distances are the same as in ferritin, and the Fe-P distance is analogous to that in another metal-ATP complex. An observable Fe-P environment in such a large polynuclear iron cluster as the Fe(III).ATP (4:1) complex indicates that the phosphate is distributed throughout rather than merely on the surface, in contrast to earlier models of chelate-stabilized iron clusters. Complexes of Fe(III) and ATP similar to those described here may form in vivo either as normal components of intracellular iron metabolism or during iron excess where the consequent alteration of free nucleotide triphosphate pools could contribute to the observed toxicity of iron.

Adenosine Triphosphate↗
PubMed1988

Pseudomelanosis duodeni.

Pseudomelanosis duodeni, speckled black pigmentation of the duodenal mucosa, presents a striking appearance at endoscopy. Among the 14 reported cases there is a predominance of black women greater than 40 years old, but it can occur in any race and age group. There is no known association with pigmentation elsewhere in the gastrointestinal tract or with the use of laxatives. However, most reported patients were hypertensive (many treated with hydralazine and propranolol) and significant numbers suffered from upper gastrointestinal bleeding, chronic renal failure, or diabetes mellitus. The pigment is usually located in mucosal macrophages, in lysosomes. Histochemical studies and electron probe microanalysis suggest that several pigments may result in this endoscopic appearance, including lipomelanin, ceroid, iron sulfide, and hemosiderin. Additional studies, possibly using tissue from surgical resections or autopsies, are needed to determine the etiology and clinical significance of this heterogeneous entity.

Adult↗
PubMed1988

Alternatives to high noble dental casting gold alloys type 3. An in vitro in vivo study.

For economic reasons a large number of cheaper alternatives to the high noble dental casting gold alloys have been introduced on the market. The main problem with these alternative alloys is their chemical stability. This is a most important property as degradation of an alloy may release substances which can be harmful to the wearer. Thus, the corrosion behavior of four dissimilar alternative dental casting alloys together with a high-gold reference alloy was evaluated in the as-cast, hardened, and annealed conditions by means of potentiodynamic polarization analysis, partly supplemented by electron spectroscopy for chemical analysis. In order to facilitate interpretation of the results of the corrosion study, the composition and metallographic structure of specimens in the specimens in the dissimilar conditions had to be determined. The methods used were light microscopy, electron probe microanalysis, and X-ray diffractometry. Biocompatibility, which is related to the release of metal ions, was evaluated by subcutaneous implantation of specimens from the five alloys in guinea-pigs. Thus, the in vivo toxicity of the different alloys could be assessed. The chemical stability of an alloy also determines its tarnish resistance and as tarnish apart from creating esthetic problems, also may result in changes in the wetting characteristics of the alloy surface the in vivo tarnish of as-cast and annealed specimens inserted into complete mandibular dentures was estimated after up to 16 weeks. Castability, an important factor in an alloy's clinical performance, was measured as the marginal sharpness of cast simulated crowns from the five alloys. Finally, the clinical performance of crowns and bridges made from one low-gold and one silver-palladium alloy as experimental materials together with a high-gold alloy as a reference material was evaluated using specific periodontal parameters, a tarnish index, and CDA's guidelines for the assessment of clinical quality. The findings may be summarized as follows: The metallographic evaluation for the low-gold alloys Midas and Rajah indicated that these alloys may contain more than one phase. The two silver-palladium alloys Albacast and Alba V were heterogeneous in the three conditions studied. In most cases, the pre-treatment of the alloys had a decisive influence on their proneness to corrosion. The castability of the silver-palladium alloys was inferior to that of the gold-based alloys. The biocompatibility as revealed by subcutaneous implantation showed that one of the silver-palladium alloys (Albacast) produced the least tissue response, while the other one (Alba V) exhibided the worst tissue response.(ABSTRACT TRUNCATED AT 400 WORDS)

Aged↗
PubMed1988

The granular layer of Tomes in experimental caries in rats.

In examination of ground sections of human third maxillary molar teeth, the granular layer of Tomes was shown to consist of expansion of dentinal tubules. The microradiographic density was decreased well inside the layer. It was postulated that the findings were expressions of dentin resorption. The theory was tested experimentally in rats fed a cariogenic diet with low calcium and phosphorus. The morphology of mandibular molar teeth was studied by electron probe microanalysis and by microradiography. It was concluded that the primary event in cariogenesis was an expansion of peripheral dentinal tubules with formation of confluent microcavities and, thus, an unmasking of the granular layer of Tomes, which normally is only potential. A subsequent loss of mineral density in the outer enamel eventually caused breakdown of the outer enamel with caries visible from the surface. The loss of density within the enamel was postulated to result from interruption of the normal flux of nutrients, metabolites and ions between the dentin and enamel. Whereas an increase in dietary calcium and phosphorus delayed and reduced significantly, but did not prevent cariogenesis, it supported the theory that experimental caries in rats is a metabolic disease with the peripheral dentin the primary target.

Adult↗
PubMed1980

Effect of anesthetics on membrane fluidity tested by two different techniques: EPR spin labels and polarization of perylene fluorescence.

We have investigated the effect of n-butanol on the spectroscopic properties of two types of probes, that are usually employed to detect membrane fluidity, in mitochondrial phospholipid vesicles and mitochondrial membranes. Although both a spin label (16-doxylstearate) and the fluorescent probe perylene detect a higher immobilization of the membrane in comparison with phospholipid vesicles, the effect of butanol in the case of the membrane is strikingly different with the two techniques employed, showing increased fluidity in the case of the spin label and decreased fluidity with the fluorescent probe.

Anesthetics↗
PubMed1983

Three-dimensional configuration of the mitochondria in cultured heart cells.

The mitochondria of chick heart cells grown in monolayer culture occupy a relatively large percentage (30%) of the cell cytoplasmic volume, as determined by thin section morphometry, and vary in their ultrastructural configuration in response to different functional states of the cell. The present study was undertaken to determine the three-dimensional structure of the mitochondria in cardiac cells, since reconstruction experiments have demonstrated the existence of a mitochondrial network in cardiac and other tissues, e.g. diaphragm, soleus and vastus muscle, kidney and urinary bladder, in vivo. Confluent monolayers of synchronously beating embryonic chick heart cells were fixed, stained with a mitochondria-specific heavy metal complex (Pb-Cu citrate), and processed for either transmission electron microscopy (TEM) or scanning electron microscopy (SEM) and backscatter electron imaging (BSI). Both secondary and backscatter images revealed the presence of many thin, extremely elongate structures which in stereo views appeared as branching, anastomosing networks. TEM demonstrated localization of the electron dense stain to either nuclear or mitochondrial membranes, structures which were easily distinguished with SEM or BSI alone. These morphological results indicate that many mitochondria of the cultured heart muscle cell are interconnected and suggest that this morphological network may represent a parallel functional unit which maintains the energy state of the cell.

Animals↗
PubMed1981

[Cast fractures of dental Ni-Cr alloys (author's transl)].

Cast fractures of Ni-Cr alloys were investigated by means of scanning electron microscopy, energy dispersive X-ray spectrometry, electron-probe microanalysis, density measurements, setting and thermal expansion measurements and compressive tests. Three-Ni-Cr alloys for crowns and bridges were cast in spiral configurations by an argon-arc pressured type or an induction argon-pressured type-casting machine. The amount of cast fracture increase with an increase in cast temperature, but not with an increase of holding time at cast temperature. Ni-Cr alloys have more cast fractures in a phosphate-bonded investment than in a gypsum-bonded cristobalite investment. Fracture surfaces have an exposed dendrite structure, indicating the presence of cast porosity. The trigger of cast crack can be a cast porosity and the propagation of crack to fracture may be mainly due to the strength of investments.

Chromium Alloys↗
PubMed1994

Light microscopy techniques for the demonstration of silicone gel.

Because of the difficulty in identifying silicone gel in histologic and cytologic specimens by means of conventional light microscopy, we investigated alternative light microscopy techniques, as well as specimen staining and preparation. Specimens from six periprosthetic capsules, one silicone granuloma specimen, and one synovial biopsy specimen obtained from women with silicone breast implants were cut at 4-, 10-, 20-, and 30-microns sections, stained with a variety of common stains, and correlated with electron probe microanalysis. In addition, a commercial silicone gel and silicone gel extracted from a previously implanted silicone breast prosthesis were smeared and examined unstained or stained with Papanicolaou and Diff Quik. Silicone was noted to be refractile, nonpolarizable, and nonstainable. Thicker sections prevented silicone "dropout" during processing and increased the contrast between stained tissue and unstained silicone (negative staining). The relative ease of silicone identification was greatly increased with non-Koehler, phase contrast, and darkfield microscopy. Staining the mounting media of hematoxylin-eosin-stained sections with a nonparticulate commercial ink allowed enhanced negative staining detection of silicone gel.

Breast↗
PubMed1993

[An experimental study on the mechanism of antiatherosclerotic effect of nifedipine].

Thirty male N-Z white rabbits were randomized into 3 groups (10 each). Normal control group (C) were fed regular chow. Atherosclerotic control group (CAS) were fed a chow containing 1% cholesterol. Nifedipine group (N) were fed 1% cholesterol chow and nifedipine 40 mg/animal/day. The experiment lasted for 12 weeks. Blood total cholesterol, HDL-C, MDA, 6-keto-PGF1 alpha and TXB2 were measured. After the sacrifice of the animals, electron probe microanalysis was employed to cryo-ultrathin sections of the aorta for measuring cytoplasmic calcium content in situ in the medial smooth muscle cells. The area of atherosclerotic plaques of the aortae was planimetried with computer. The results showed that MDA and TXB2 in group CAS were markedly higher than those in groups C and N (P < 0.01 or 0.05). The cytoplasmic calcium in group CAS was significantly higher than that in groups C and N (P < 0.01). The difference between groups C and N was not significant. The area of atherosclerotic lesions in group CAS was 44 +/- 8%, markedly larger than that in group N (13 +/- 5%, P < 0.01). The antiatherosclerotic effects of nifedipine may be mainly by a mechanism of inhibiting intracellular calcium overload.

Animals↗
PubMed1993

Inhibition of enzymes by short-wave optical radiation and its effect on the retina.

UNLABELLED: INTRODUCTION AND HYPOTHESES: Exposure to short-wave optical radiation is a potential hazard for vision. In the present study, blue-light damage is studied in rat retina. It was hypothesized that the absorption of blue light by cytochrome oxidase in rat retina inhibits this enzyme, and may reduce the retinal oxidative metabolism. Irreversible inhibition of the oxidative metabolism may decrease the activity of the Na/K-ATPase, hence redistribute ions, increase intracellular osmotic pressure and cause cellular edema. Severe retinal edema may be the cause of retinal degeneration. METHODS: A quantitative histochemical method, a combination of histochemical staining and densitometrical measurement, was established to measure the activity of cytochrome oxidase. The distribution of chlorine and potassium in rat retina was estimated with a nuclear microprobe. Microradiography was adopted for measuring the protein and lipid density, which is an indirect estimation of retinal edema and retinal refractive index. The damage to the photoreceptor cells was estimated from the thickness of the outer nuclear layer. RESULTS AND CONCLUSIONS: Blue light inhibited cytochrome oxidase at a retinal dose of about 110 kJ/m2. This inhibition was reversible, and is probably related to the light regulation of retinal metabolism. At a retinal dose of about 380 kJ/m2, the inhibition of cytochrome oxidase was followed consecutively by a probable redistribution of chlorine and potassium in the inner and outer segments, damage to the mitochondria in the inner segments, edema in the inner and outer segments, and progressive degeneration of photoreceptor cells. Dark adaptation did not increase the blue-light retinal injury. These findings support the hypothesis that inhibition of cytochrome oxidase is one of the causes of blue-light retinal damage. The alteration of enzyme kinetics after in vitro exposure to short-wave optical radiation was estimated using lactate dehydrogenase as a model. The ultraviolet-radiation exposure inhibited lactate dehydrogenase with a significant decrease in maximal velocity, while Michaelis constant remained unchanged.

Animals↗