Stereological principles provide efficient and reliable tools for the determination of quantitative parameters of tissue structure on sections. Some principles which allow the estimation of volumetric ratios, surface areas, surface-to-volume ratios, thicknesses of tissue or cell sheets, and the number of structures are reviewed and presented in general form; means for their practical application in electron microscopy are outlined. The systematic and statistical errors involved in such measurements are discussed.

/pdf/practical-stereological-methods-for-morphometric-cytology-2iosekelug.pdf

Practical stereological methods for morphometric cytology.

The basic morphological properties of liver cells are defined in the form of a morphometric model to permit integrated quantitative characterization of functionally important parameters. Stereologic methods which allow efficient and reliable quantitative evaluation of sectioned liver tissue are presented. Material, obtained by a rigorous three-stage sampling procedure from five normal rat livers, is systematically subjected to this analysis at four levels of magnification. This yields quantitative data which are expressed as "densities," i.e. content per 1 ml of tissue, as "specific dimensions" related to 100 g body weight, and as absolute dimensions per average "mononuclear" hepatocyte. Base line data relating to the normal rat liver are presented for the entire spectrum of parameters. As examples, 1 ml of liver tissue contains 169 x 106 hepatocyte nuclei, some 90 x 106 nuclei of other cells, and 280 x 109 mitochondria. Hepatocyte cytoplasm accounts for 77% of liver volume, and the mitochondria for 18%. The surface area of endoplasmic reticulum membranes in 1 ml of liver tissue measures 11 m2 of which are ⅔ of the rough form carrying some 2 x 1013 ribosomes. The surface area of mitochondrial cristae in the unit volume is estimated at 6 m2. The validity and applicability of the method are discussed, and the data are compared with available information from other studies.

/pdf/correlated-morphometric-and-biochemical-studies-on-the-liver-2toagnzmfh.pdf

CORRELATED MORPHOMETRIC AND BIOCHEMICAL STUDIES ON THE LIVER CELL I. Morphometric Model, Stereologic Methods, and Normal Morphometric Data for Rat Liver

Objective To assess the in vivo intracanal microbial status of apical root canal system of mesial roots of human mandibular first molars with primary apical periodontitis immediately after one-visit endodontic treatment. The residual intracanal infection was confirmed by correlative light and transmission electron microscopy. Study design Sixteen diseased mesial roots of mandibular first molars were treated endodontically, each in one visit. Mesio-buccal canals were instrumented using stainless steel hand files and mesio-lingual canals with a nickel-titanium rotary system. The canals were irrigated with 5.25% sodium hypochlorite (NaOCl) during the instrumentation procedures, rinsed with 10 mL of 17% ethylenediamine tetraacetic acid (EDTA), and obturated with gutta-percha and zinc oxide eugenol cement. Thereafter, the apical portion of the root of each tooth was removed by flap-surgery. The specimens were fixed, decalcified, subdivided in horizontal plane, embedded in plastic, processed, and evaluated by correlative light and transmission electron microscopy. Results Fourteen of the 16 endodontically treated teeth revealed residual intracanal infection after instrumentation, antimicrobial irrigation, and obturation. The microbes were located in inaccessible recesses and diverticula of instrumented main canals, the intercanal isthmus, and accessory canals, mostly as biofilms. Conclusions The results show (1) the anatomical complexity of the root canal system of mandibular first molar roots and (2) the organization of the flora as biofilms in inaccessible areas of the canal system that cannot be removed by contemporary instruments and irrigation alone in one-visit treatment. These findings demonstrate the importance of stringent application of all nonantibiotic chemo-mechanical measures to treat teeth with infected and necrotic root canals so as to disrupt the biofilms and reduce the intraradicular microbial load to the lowest possible level so as to expect a highly favorable long-term prognosis of the root canal treatment.

Microbial status of apical root canal system of human mandibular first molars with primary apical periodontitis after “one-visit” endodontic treatment

Pathology of lung cancer.

Particle biokinetics is important in hazard identification and characterization of inhaled particles. Such studies intend to convert external to internal exposure or biologically effective dose, and may help to set limits in that way. Here we focus on the biokinetics of inhaled nanometer sized particles in comparison to micrometer sized ones.The presented approach ranges from inhaled particle deposition probability and retention in the respiratory tract to biokinetics and clearance of particles out of the respiratory tract. Particle transport into the blood circulation (translocation), towards secondary target organs and tissues (accumulation), and out of the body (clearance) is considered. The macroscopically assessed amount of particles in the respiratory tract and secondary target organs provides dose estimates for toxicological studies on the level of the whole organism. Complementary, microscopic analyses at the individual particle level provide detailed information about which cells and subcellular components are the target of inhaled particles. These studies contribute to shed light on mechanisms and modes of action eventually leading to adverse health effects by inhaled nanoparticles.We review current methods for macroscopic and microscopic analyses of particle deposition, retention and clearance. Existing macroscopic knowledge on particle biokinetics and microscopic views on particle organ interactions are discussed comparing nanometer and micrometer sized particles. We emphasize the importance for quantitative analyses and the use of particle doses derived from real world exposures.

/pdf/deposition-and-biokinetics-of-inhaled-nanoparticles-1uuingdz22.pdf

Deposition and biokinetics of inhaled nanoparticles

For more than 2 years, a double-staining of sections of OsO 4-fixed and Epon-embedded tissues with uranyl acetate followed by lead hydroxide has been routine technique in this laboratory. It was found to give substantially higher contrast, thus permitting the use of thinner sections. It facilitated focusing and routinely provided clearer pictures of cell fine structure than could be obtained with either stain alone. However, the formation of a fine precipitate frequently marred the sections, and this difficulty could never be satisfactorily controlled. Apparently, it is caused by the uranyl acetate solution which is not stable at the pH and concentration used. Decreasing the concentration and/or the pH of the solution caused an undesirable loss of staining intensity. Therefore, a number of different uranyl salts were tested as a substitute for uranyl acetate in the procedure, and one of them, uranyl magnesium acetate, has been found to give consistently good results.

https://rupress.org/jcb/article-pdf/25/1/157/1382320/157.pdf

A routine technique for double-staining ultrathin sections using uranyl and lead salts.

Presence of Asbestos Bodies in Organs Other than the Lung

Electron microscopic observations of the bronchial epithelium of dogs. II. Smoking dogs.

Forty-nine cases of lung tumor were initially classified according to the World Health Organization (WHO) system by light microscopy. Additional study by electron microscopy using only a minimum of ultrastructural features as criteria for each type made more precise classification of some of the poorly differentiated or undifferentiated tumors possible. Most significant was the finding of evidence of a second tumor type in nine of the 35 tumors previously classified as moderately to well differentiated thus reclassifying them as mixed tumors. Sixteen of the 49 tumors were reclassified and a more precise classification was made in five others. Only two cases of undifferentiated small cell tumors were available and no unequivocal neurosecretory granules could be found in either. Correlation of the more precise typing of lung tumors by electron microscopy with the clinical data and modes of therapy will provide necessary information for determining the usefulness of the WHO classification.

Verta R. Parks

Papers

A routine technique for double-staining ultrathin sections using uranyl and lead salts.

Presence of Asbestos Bodies in Organs Other than the Lung

Electron microscopic observations of the bronchial epithelium of dogs. II. Smoking dogs.

A comparison of World Health Organization (WHO) classification of lung tumors by light and electron microscopy.

Electron microscopic observations of the bronchial epithelium of dogs