scholarly journals THE STRANDEDNESS OF MEIOTIC CHROMOSOMES FROM ONCOPELTUS

1966 ◽  
Vol 31 (1) ◽  
pp. 31-42 ◽  
Author(s):  
Stephen L. Wolfe ◽  
Godfrey M. Hewitt
Keyword(s):  
Electron Microscope ◽  
Critical Point ◽  
Living Cells ◽  
Point Method ◽  
Oncopeltus Fasciatus ◽  
Langmuir Trough ◽  
Ringer’S Solution ◽  
Meiotic Chromosomes ◽  
Parallel Folding

Meiotic chromosomes were isolated from male Oncopeltus fasciatus by dissecting the testes under insect Ringer's solution and spreading the living cells on the Langmuir trough. After being dried by the critical point method, preparations were examined under the electron microscope. Chromosomes at all stages of prophase prove to be multistranded. A significant increase in the number of parallel 250 A fibers in the chromosomes occurs between zygotene and diakinesis. Parallel folding, rather than true multistrandedness, is interpreted as the mechanism responsible for this observed increase in multistrandedness. It has not been possible to determine whether the multistrandedness observed at leptotene represents true multistrandedness or is the result of parallel folding. Apparent multistrandedness is lost at metaphase when the 250 A fibers of the chromosomes become coiled more tightly. In preparations isolated by these methods, no structures other than the 250 A chromosome fibers are visible in the chromomeres, which appear as regionally coiled or folded areas of the fibers along the arm of the chromosome.

scholarly journals THE HUMAN CHROMOSOME

1969 ◽  
Vol 41 (1) ◽  
pp. 73-90 ◽  
Author(s):  
J. G. Abuelo ◽  
Dorothy E. Moore
Keyword(s):  
Tissue Culture ◽  
Electron Microscope ◽  
Human Chromosome ◽  
Critical Point ◽  
Human Lymphocytes ◽  
Langmuir Trough ◽  
Trypsin Treatment ◽  
Short Term ◽  
Dnase Digestion ◽  
Critical Point Drying

Human lymphocytes were grown in short-term tissue culture and were arrested in metaphase with Colcemid. Their chromosomes were prepared by the Langmuir trough-critical point drying technique and were examined under the electron microscope. In addition, some chromosomes were digested with trypsin, Pronase, or DNase. The chromosomes consist entirely of tightly packed, 240 ± 50-A chromatin fibers. Trypsin and Pronase treatments induce relaxation of fiber packing and reveal certain underlying fiber arrangements. Furthermore, trypsin treatment demonstrates that the chromatin fiber has a 25–50 A trypsin-resistant core surrounded by a trypsin-sensitive sheath. DNase digestion suggests that this core contains DNA.

scholarly journals THE EFFECT OF PREFIXATION ON THE DIAMETER OF CHROMOSOME FIBERS ISOLATED BY THE LANGMUIR TROUGH-CRITICAL POINT METHOD

1968 ◽  
Vol 37 (3) ◽  
pp. 610-620 ◽  
Author(s):  
Stephen L. Wolfe
Keyword(s):  
Critical Point ◽  
Average Diameter ◽  
Point Method ◽  
Root Tip ◽  
Langmuir Trough

The effect of prefixation on the diameter of chromosome fibers isolated by the Langmuir trough-critical point method has been investigated in several species of plants and animals. In barley, fibers isolated from endosperm without prefixation have an average diameter of between 240 and 250 A, and are similar in dimensions and structure to the chromosome fibers isolated from animals by this method. Chromosome fibers from other tissues of the same plant are smaller in diameter when isolated without prefixation, approximating 200 A. After prefixation in 2% buffered formalin, isolated fibers from the three barley tissues studied are reduced in diameter, to approximately 120–130 A for endosperm and leaflet and to 140 A for root tip. Chromosome fibers isolated from newt erythrocytes also show a significantly reduced diameter after formalin prefixation, to approximately 120 A.

Scanning Electron Microscopy of Dried and Acid Treated Shells of Difflugia

1973 ◽  
Vol 31 ◽  
pp. 448-449
Author(s):  
Barry S. Eckert ◽  
S. M. McGee-Russell
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Critical Point ◽  
Point Method ◽  
External Structure ◽  
Cell Locomotion ◽  
Single Opening ◽  
Scanning Electron

Difflugia lobostoma is a shelled amoeba. The shell is an external structure of considerable mass which presents the animal with special restrictions in cell locomotion which are met by the development of active pseudopodial lobopodia containing, apparently, an organized system of thick and thin microfilaments (Eckert and McGee-Russell, 1972). The shell is constructed of sand grains picked up from the environment, and cemented into place with a secretion. There is a single opening through which lobopods extend. The organization of the shell was studied by scanning electron microscopy (SEM).Intact shells or animals with shells were dried by the critical point method of Anderson (1966) or air dried, after primary fixation in glutaraldehyde.

Pulmonary microcirculation: tubules rather than sheet and post

1982 ◽  
Vol 53 (2) ◽  
pp. 510-515 ◽  
Author(s):  
W. G. Guntheroth ◽  
D. L. Luchtel ◽  
I. Kawabori
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Critical Point ◽  
Ringer Solution ◽  
Basic Component ◽  
Pulmonary Vasculature ◽  
Critical Point Drying ◽  
Pulmonary Microcirculation ◽  
Scanning Electron

We examined latex casts of the pulmonary microcirculation with the scanning electron microscope (SEM). Mature rats were anesthetized and ventilated; the pulmonary vasculature was washed out with lactated Ringer solution and then filled with a mixture of Geon latexes. The airways were filled with glutaraldehyde with resulting transmural vascular pressures of 10 cmH2O. After critical-point drying and corrosive removal of the lung tissue, SEM studies of the vascular replicas revealed two distinct patterns of pulmonary microcirculation: 1) sparse, long, tubular capillaries that comprise the thin subpleural layer and appear as “filler” in the peribronchial spaces; and 2) alveolar microcirculation that is composed of tightly matted, intersecting tubules, shorter but of the same diameter as type 1, in spherical array in two layers. The alveolar capillaries at low magnification appear superficially as sheets; however, the detailed morphology is not consistent with the sheet-and-post model. We conclude that the basic component of the pulmonary microcirculation is tubular and not different from other capillary beds except in density.

scholarly journals The electrophysiological mapping of compartments within a mammalian cell.

1977 ◽  
Vol 72 (1) ◽  
pp. 86-103 ◽  
Author(s):  
D Giulian ◽  
E G Diacumakos
Keyword(s):  
Electron Microscope ◽  
Electrical Properties ◽  
Intact Cell ◽  
Living Cells ◽  
Microscope Examination ◽  
New Approach ◽  
Golgi Region ◽  
Grounding Electrode ◽  
Combination Of Methods ◽  
Peak Value

The electrical properties of structures within an intact cell were examined by impalement with micropipette electrodes. Mean potential differences (PDs) measured from interphase HeLa cells showed that internal membrane-bounded compartments such as the nucleus, Golgi region, and the mitochondria were more negative than the cytoplasm with respect to an external grounding electrode. The nuclear PDs, unlike Golgi and cytoplasmic PDs, shifted during interphase and reached a peak value shortly before mitosis. The positioning of micropipettes was confirmed by electron microscope examination of marker solutions that were microinjected into specific intracellular regions. The combination of methods described here offers a new approach for the study of physiological events within intact, living cells.

A comparison of microstructures of Cheddar cheese curd manufactured with calf rennet, bovine pepsin, and porcine pepsin

1976 ◽  
Vol 43 (1) ◽  
pp. 113-115 ◽  
Author(s):  
M. F. Eino ◽  
D. A. Biggs ◽  
D. M. Irvine ◽  
D. W. Stanley
Keyword(s):  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Critical Point ◽  
Cheddar Cheese ◽  
Microscope Examination ◽  
Porcine Pepsin ◽  
Electron Microscope Examination ◽  
Critical Point Drying ◽  
Cheese Curd ◽  
Scanning Electron

SummaryCalf rennet, bovine pepsin, and porcine pepsin were used to produce cheese curd, using the same milk and lactic culture for each. Specimens were prepared for scanning electron microscope examination by a modified critical-point drying technique.From examination of the micrographs, the curd made with bovine and porcine pepsin were similar in structure and in orientation of the coagulated protein, whereas the curd produced with rennet was different, having a more compact and organized structure.

Über Desoxyribonucleinsäure-Molekeln in Protein-Mischfilme

1959 ◽  
Vol 14 (12) ◽  
pp. 770-779 ◽  
Author(s):  
A. Kleinschmidt ◽  
H. Rüter ◽  
W. Hellmann ◽  
R. K. Zahn ◽  
A. Docter ◽  
...  
Keyword(s):  
Electron Microscope ◽  
Bovine Serum Albumin ◽  
Serum Albumin ◽  
Bovine Serum ◽  
Deoxyribonucleic Acid ◽  
Carbon Support ◽  
Dna Molecules ◽  
Langmuir Trough ◽  
Surface Monolayers

A nucleoprotein of a vitrous consistency was extracted from the gonads of the coalfish (Gadus virens).The preparation of deoxyribonucleic acid (DNA) from this nucleoprotein and from staphylococci is described. Both of these different kinds of DNA have been mixed with bovine serum albumin or cytochrom c respectively to produce solutions which subsequently were spread onto the Langmuir trough under defined conditions.After transfer of aliquots from the surface monolayers to carbon support films the preparations were examined with the electron microscope. The micrographs show threads of various lengths, partly stretched, partly folded in loops, consisting of DNA molecules embedded in a protein envelope.Measurements and calculations of 5900 particles of the complex of Gadus virens-DNA-Albumin, with relatively short threads show a distribution of discontinuous character. If length is plotted against number then it occurs that there are maxima of different lengths of threads. The abscissae of these maxima obey the ratio 1 : 2 : 4 : 8. This holds for longer threads too the maxima of which, however, have smaller ordinate values.

Scanning electron microscopy of meiotic chromosomes of plants in situ

1974 ◽  
Vol 52 (6) ◽  
pp. 1438-1440 ◽  
Author(s):  
Ernest D. P. Whelan ◽  
G. H. Haggis ◽  
E. J. Ford ◽  
B. Dronzek
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Solanum Tuberosum ◽  
Electron Microscope ◽  
Scanning Electron Microscope ◽  
Solanum Tuberosum L ◽  
Meiotic Spindle ◽  
Meiotic Chromosomes ◽  
Scanning Electron

Scanning electron microscope studies of anthers of the Asiatic Lilium hybrid Enchantment and Solanum tuberosum L. cv. Netted Gem fixed in organic acid – alcohol type fixatives clearly revealed nucleoli, bivalents, and the meiotic spindle. Centromere regions could not be identified in pachytene bivalents, but areas of possible spindle attachment were evident for metaphase I – anaphase I bivalents.

Sign in / Sign up

Export Citation Format

Share Document