scholarly journals KINETOPLAST DEOXYRIBONUCLEIC ACID OF THE HEMOFLAGELLATE TRYPANOSOMA LEWISI

1970 ◽  
Vol 47 (3) ◽  
pp. 689-702 ◽  
Author(s):  
Hartmut C. Renger ◽  
David R. Wolstenholme
Keyword(s):  
Electron Microscope ◽  
Ethidium Bromide ◽  
Thermal Denaturation ◽  
Deoxyribonucleic Acid ◽  
Cesium Chloride ◽  
Kinetoplast Dna ◽  
Microscope Examination ◽  
Main Band ◽  
Trypanosoma Lewisi ◽  
High Degree

Cesium chloride centrifugation of DNA extracted from cells of blood strain Trypanosoma lewisi revealed a main band, ρ = 1.707, a light satellite, ρ = 1.699, and a heavy satellite, ρ = 1.721. Culture strain T. lewisi DNA comprised only a main band, ρ = 1.711, and a light satellite, ρ = 1.699. DNA isolated from DNase-treated kinetoplast fractions of both the blood and culture strains consisted of only the light satellite DNA. Electron microscope examination of rotary shadowed preparations of lysates revealed that DNA from kinetoplast fractions was mainly in the form of single 0.4 µ circular molecules and large masses of 0.4 µ interlocked circles with which longer, often noncircular molecules were associated. The 0.4 µ circular molecules were mainly in the covalently closed form: they showed a high degree of resistance to thermal denaturation which was lost following sonication; and they banded at a greater density than linear DNA in cesium chloride-ethidium bromide gradients. Interpretation of the large masses of DNA as comprising interlocked covalently closed 0.4 µ circles was supported by the findings that they banded with single circular molecules in cesium chloride-ethidium bromide gradients, and following breakage of some circles by mild sonication, they disappeared and were replaced by molecules made up of low numbers of apparently interlocked 0.4 µ circles. When culture strain cells were grown in the presence of either ethidium bromide or acriflavin, there was a loss of stainable kinetoplast DNA in cytological preparations. There was a parallel loss of light satellite and of circular molecules from DNA extracted from these cells.

scholarly journals Physicochemical properties of kinetoplast DNA from Crithidia acanthocephali. Crithidia luciliae, and Trypanosoma lewisi.

1975 ◽  
Vol 67 (2) ◽  
pp. 378-399 ◽  
Author(s):  
D L Fouts ◽  
J E Manning ◽  
D R Wolstenholme
Keyword(s):  
Base Composition ◽  
Unit Length ◽  
Buoyant Density ◽  
Cesium Chloride ◽  
Kinetoplast Dna ◽  
Molar Ratios ◽  
Trypanosoma Lewisi ◽  
Crithidia Luciliae ◽  
Sequence Homologies ◽  
Thermal Melting

The protozoa Crithidia and Trypanosoma contain within a mitochondrion a mass of DNA known as kinetoplast DNA (kDNA) which consists mainly of an association of thousands of small circular molecules of similar size held together by topological interlocking. Using kDNA from Crithidia acanthocephali, Crithidia luciliae, and Trypanosoma lewisi, physicochemical studies have been carried out with intact associations and with fractions of covalently closed single circular molecules, and of open single circular and unit length linear molecules obtained from kDNA associations by sonication, sucrose sedimentation, and cesium chloride-ethidium bromide equilibrium centrifugation. Buoyant density analyses failed to provide evidence for base composition heterogeneity among kDNA molecules within a species. The complementary nucleotide strands of kDNA molecules of all three species had distinct buoyant densities in both alkaline and neutral cesium chloride. For C. acanthocephali kDNA, these buoyant density differences were shown to be a reflection of differences in base composition between the complementary nucleotide strands. The molar ratios of adenine: thymine:guanine:cytosine, obtained from deoxyribonucleotide analyses were 16.8:41.0:28.1:14.1 for the heavy strand and 41.6:16.6:12.8:29.0 for the light strand. Covalently closed single circular molecules of C. acanthocephali (as well as intact kDNA associations of C. acanthocephali and T. lewisi) formed a single band in alkaline cesium chloride gradients, indicating their component nucleotide strands to be alkaline insensitive. Data from buoyant density, base composition, and thermal melting analyses suggested that minor bases are either rare or absent in Crithidia kDNA. The kinetics of renaturation of 32P labeled C. acanthocephali kDNA measured using hydroxyapatite chromatography were consistent with at least 70% of the circular molecules of this DNA having the same nucleotide sequence. Evidence for sequence homologies among the kDNAs of all three species was obtained from buoyant density analyses of DNA in annealed mixtures containing one component kDNA strand from each of two species.

NUCLEIC ACID METABOLISM IN INTESTINAL MUCOSA: V. HETEROGENEITY OF DEOXYRIBONUCLEIC ACID ISOLATED FROM THE INTESTINAL MUCOSA OF THE RAT

1967 ◽  
Vol 45 (3) ◽  
pp. 375-386
Author(s):  
C. Mezei ◽  
S. H. Zbarsky
Keyword(s):  
Intestinal Mucosa ◽  
Enzymatic Degradation ◽  
Thermal Denaturation ◽  
Deoxyribonucleic Acid ◽  
Acid Metabolism ◽  
Cesium Chloride ◽  
Nucleic Acid Metabolism ◽  
Dna Molecule ◽  
Physical Chemical ◽  
The Individual

Doubly labeled DNA was isolated from the intestinal mucosa of rats injected intravenously with 3H-thymidine and 24 hours later with 14C-thymidine. The DNA was chromatographed on columns of methylated albumin–kieselguhr. The 3H/14C ratios of the individual subfractions comprising the main DNA fraction eluted from the column increased from the earlier to the later sub-fractions in the DNA isolated from rats receiving the 14C-labeled thymidine 20 minutes before they were killed. This result indicated a slower incorporation of the 14C-labeled material into the DNA molecules represented by the later sub-fractions. In experiments in which the interval before the death of the animals was extended to 40 minutes, the 3H/14C ratios were constant throughout the main DNA fraction. Enzymatic degradation of the doubly labeled DNA indicated that incorporation of both types of precursors had occurred well within the DNA molecule. Physical chemical differences were also detected among the subfractions. There appeared to be two main types of DNA which could be grouped according to thermal denaturation temperatures (Tm), and ultracentrifugation in cesium chloride gave evidence of differences in buoyant densities between the leading and final subfractions.

Selective Sampling and Orientation of Non-Homogeneous Tissues

1968 ◽  
Vol 26 ◽  
pp. 98-99
Author(s):  
C. C. Clawson ◽  
L. W. Anderson ◽  
R. A. Good
Keyword(s):  
Electron Microscopy ◽  
Electron Microscope ◽  
Light Microscopy ◽  
Random Sampling ◽  
New Method ◽  
Microscope Examination ◽  
Small Areas ◽  
Selective Sampling ◽  
Large Numbers ◽  
Specific Orientation

Investigations which require electron microscope examination of a few specific areas of non-homogeneous tissues make random sampling of small blocks an inefficient and unrewarding procedure. Therefore, several investigators have devised methods which allow obtaining sample blocks for electron microscopy from region of tissue previously identified by light microscopy of present here techniques which make possible: 1) sampling tissue for electron microscopy from selected areas previously identified by light microscopy of relatively large pieces of tissue; 2) dehydration and embedding large numbers of individually identified blocks while keeping each one separate; 3) a new method of maintaining specific orientation of blocks during embedding; 4) special light microscopic staining or fluorescent procedures and electron microscopy on immediately adjacent small areas of tissue.

New Aspects in the Design of Electron Optical Magnification Systems

1972 ◽  
Vol 30 ◽  
pp. 606-607
Author(s):  
Willem H.J. Andersen
Keyword(s):  
Electron Microscope ◽  
Imaging System ◽  
Chromatic Aberration ◽  
Research Tool ◽  
Energy Losses ◽  
Objective Lens ◽  
Theoretical Limit ◽  
Optical Magnification ◽  
Chromatic Aberrations ◽  
High Degree

Electron microscope design, and particularly the design of the imaging system, has reached a high degree of perfection. Present objective lenses perform up to their theoretical limit, while the whole imaging system, consisting of three or four lenses, provides very wide ranges of magnification and diffraction camera length with virtually no distortion of the image. Evolution of the electron microscope in to a routine research tool in which objects of steadily increasing thickness are investigated, has made it necessary for the designer to pay special attention to the chromatic aberrations of the magnification system (as distinct from the chromatic aberration of the objective lens). These chromatic aberrations cause edge un-sharpness of the image due to electrons which have suffered energy losses in the object.There exist two kinds of chromatic aberration of the magnification system; the chromatic change of magnification, characterized by the coefficient Cm, and the chromatic change of rotation given by Cp.

Feasibility of Molecular Structure Determination With a High Resolution Electron Microscope

1968 ◽  
Vol 26 ◽  
pp. 338-339
Author(s):  
T. A. Welton
Keyword(s):  
Electron Microscope ◽  
Substrate Surface ◽  
Helical Axis ◽  
Base Plane ◽  
Resolution Electron ◽  
High Resolution Electron Microscope ◽  
High Degree ◽  
Degree Of Order ◽  
Purine Pyrimidine

An ultimate design goal for an improved electron microscope, aimed at biological applications, is the determination of the structure of complex bio-molecules. As a prototype of this class of problems, we propose to examine the possibility of reading DNA sequence by an imaginable instrument design. This problem ideally combines absolute importance and relative simplicity, in as much as the problem of enzyme structure seems to be a much more difficult one.The proposed technique involves the deposition on a thin graphite lamina of intact double helical DNA rods. If the structure can be maintained under vacuum conditions, we can then make use of the high degree of order to greatly reduce the work involved in discriminating between the four possible purine-pyrimidine arrangements in each base plane. The phosphorus atoms of the back bone form in projection (the helical axis being necessarily parallel to the substrate surface) two intertwined sinusoids. If these phosphorus atoms have been located up to a certain point on the molecule, we have available excellent information on the orientation of the base plane at that point, and can then locate in projection the key atoms for discrimination of the four alternatives.

Mesophilic mutants of an obligate psychrophile, Micrococcus cryophilus

1969 ◽  
Vol 15 (10) ◽  
pp. 1145-1150 ◽  
Author(s):  
P-C. Tai ◽  
H. Jackson
Keyword(s):  
Growth Temperature ◽  
Metabolic Pathways ◽  
Thermal Denaturation ◽  
Deoxyribonucleic Acid ◽  
Elevated Temperatures ◽  
Maximum Growth ◽  
Maximal Growth ◽  
Denaturation Temperature ◽  
Maximum Growth Temperature ◽  
Thermal Denaturation Temperature

Several mutants with elevated maximal growth temperature (MGT) were developed from an obligate psychrophile, Micrococcus cryophilus ATCC 15174, by ultraviolet irradiation. Two of the mutants, T8 and M19, have the most similar characteristics to those of their parent. The mutants lost the ability to grow well at 0 °C and showed changes in metabolic pathways while acquiring the ability to grow at elevated temperatures. Heat resistance and deoxyribonucleic acid thermal denaturation temperature were shown to be unrelated to maximum growth temperature. The significance of the mutants is discussed.

A histological examination of the holding sacs and glandular scent organs of some bat species (Emballonuridae, Hipposideridae, Phyllostomidae, Vespertilionidae, and Molossidae)

2000 ◽  
Vol 78 (4) ◽  
pp. 613-623 ◽  
Author(s):  
William MR Scully ◽  
M B Fenton ◽  
A SM Saleuddin
Keyword(s):  
Electron Microscope ◽  
Sexual Dimorphism ◽  
Sebaceous Glands ◽  
Microscope Examination ◽  
Scent Gland ◽  
Light Microscope Level ◽  
Histological Techniques ◽  
Saccopteryx Bilineata ◽  
The Face ◽  
Scanning Electron

Using histological techniques at the light-microscope level, we examined and compared structure and sexual dimorphism of the wing sacs and integumentary glandular scent organs of 11 species of microchiropteran bats. The antebrachial wing sacs of the Neotropical emballonurids Peropteryx macrotis, Saccopteryx bilineata, and Saccopteryx leptura differed in size and location but lacked sudoriferous and sebaceous glands, confirming that they were holding sacs rather than glandular scent organs. Glandular scent organs from 11 species consisted of sebaceous and (or) sudoriferous glands in emballonurids (P. macrotis, S. bilineata, S. leptura, Taphozous melanopogon, Taphozous nudiventris), hipposiderids (Hipposiderous fulvus, Hipposiderous ater), the phyllostomid Sturnira lilium, the vespertilionid Rhogeessa anaeus, and molossids (Molossus ater and Molossus sinaloe). Glandular scent organs were located on the face (H. fulvus, H. ater), gular region (S. bilineata, P. macrotis, T. melanopogon, M. ater, M. sinaloe), chest (T. nudiventris), shoulder (S. lilium), or ears (R. anaeus). Glandular scent organs showed greater similarities within than between families, and typically were rudimentary or lacking in females. Scanning electron microscope examination revealed that the hairs associated with glandular areas of male T. melanopogon were larger and had a different cuticular-scale pattern than body hairs. These were osmetrichia, hairs specialized for holding and dispersing glandular products. In S. lilium, hairs associated with the shoulder scent-gland area were larger than body hairs but similar in cuticular-scale pattern.

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