A new generation of the IMAGIC image processing system.

Molecular biology of microbial ureases.

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

Molecular structure determination by electron microscopy of unstained crystalline specimens.

Two DNA binding guanine-specific antibiotics, chromomycin A3 (CMA) and the closely related mithramycin (MM), were used as chromosome fluorescent dyes. Root-tip metaphase chromosomes of three plant species and human metaphase chromosomes were sequentially stained with CMA or MM and the DNA binding AT-specific fluorochrome 4'-6-diamidino-2-phenylindole (DAPI). In some cases a non-fluorescent counterstain was used as contrasting agent: methyl green in conjunction with CMA, and actinomycin D (AMD) in combination with DAPI.--In all three plant species, Vicia faba, Scilla siberica, and Ornithogalum caudatum, the nucleolus organiser regions and/or associated heterochromatin displayed very bright fluorescence with CMA and MM and, in general, heterochromatic segments (C-bands) which were bright with CMA and MM were pale with DAPI whereas segments which were dim with CMA and MM displayed very bright fluorescence with DAPI.--Human metaphase chromosomes showed a small longitudinal differentiation in CMA fluorescence, which was essentially the reverse of the banding pattern obtained with AMD/DAPI double-staining, but of lower contrast. The cma-banding pattern appears to be similar to the pattern found by R-banding procedures.

Reverse fluorescent chromosome banding with chromomycin and DAPI.

Specimen damage caused by the beam of the transmission electron microscope, a correlative reconsideration.

A photometric procedure for rapid determination of weight of isolated particles down to a size of 200 A is described. Under normal conditions of electron microscopy, weights of down to 10−18 g can be determined with an inaccuracy of less than 10%. By lowering the accuracy or using more elaborate measures (such as very low accelerating voltage) one to two orders of magnitude for the lower weight limit can be gained. The method can now be applied to population studies of biologic particles, especially those of inhomogeneous and odd‐shaped entities. Individual losses of matter through the action of enzymes and the uptake of specific stains can be measured quantitatively. The method extends the possibilities of individual mass‐weight determination to the biologically important region of submicroscopic particles.

A Photometric Procedure for Weight Determination of Submicroscopic Particles Quantitative Electron Microscopy

The electron microscope has been used to determine the weight distribution of isolated subcellular particles from normal rat liver. The following results are reported: (1) There exist at least two well defined weight populations of subcellular particles; their respective median weights are 1.3 x 10-14 and 11 x 10-14 gm. The lighter fraction is considered to consist of lysosomes, the heavier of mitochondria. (2) The mitochondrial fraction shows a log-normal distribution of the particle weight. (3) By the introduction of morphologic criteria, the mitochondrial fraction is divided into two groups, one consisting of a spherical, the other of an oblong type of particle. The data found support the following concepts: (a) Mitochondria increase their weight from a certain size up by linear growth. (b) Mitochondria divide. The division is not necessarily symmetric; in all cases, however, one part of the division product is a spherical particle. It is felt that these results constitute a valuable demonstration of the general capabilities of quantitative electron microscopy and may stimulate many other useful applications of this technique in cytology, bacteriology, and virology.

/pdf/study-of-mitochondria-in-rat-liver-quantitative-electron-54a61mz7mi.pdf

Study of mitochondria in rat liver. Quantitative electron microscopy.

Considerations of volume, mass, DNA, and arrangement of mitochondria in the midpiece of bull spermatozoa.

Isolated human chromosomes dried by the critical-point method have been assumed to retain their original three-dimensional shape when viewed under a transmission electron microscope. Our scanning electron microscopic study confirms this interpretation and reveals an appearance like that of a skein of yarn. The existence of fiber bridges between chromatid pairs and among chromosomes is demonstrated.

https://science.sciencemag.org/content/sci/171/3975/1024.full.pdf

G.F. Bahr

Papers

Specimen damage caused by the beam of the transmission electron microscope, a correlative reconsideration.

A Photometric Procedure for Weight Determination of Submicroscopic Particles Quantitative Electron Microscopy

Study of mitochondria in rat liver. Quantitative electron microscopy.

Considerations of volume, mass, DNA, and arrangement of mitochondria in the midpiece of bull spermatozoa.

Scanning Electron Microscopic Observations of Surface Structure of Isolated Human Chromosomes