scholarly journals CHEMICAL AND MORPHOLOGICAL STUDIES OF BACTERIAL SPORE FORMATION

1962 ◽  
Vol 12 (1) ◽  
pp. 115-133 ◽  
Author(s):  
I. Elizabeth Young ◽  
Philip C. Fitz-James
Keyword(s):  
Phase Contrast ◽  
Calcium Uptake ◽  
Dipicolinic Acid ◽  
Double Layers ◽  
Dark Phase ◽  
Chemical Methods ◽  
Thin Sections ◽  
Morphological Studies ◽  
Water Suspensions ◽  
Free Spore

From the stage of a completed membranous forespore to that of a fully ripened free spore, synchronously sporulating cells of a variant Bacillus cereus were studied by cytological and chemical methods. Particular attention was paid to the development of the three spore layers—cortex, coat, and exosporium—in relation to the forespore membrane. First, the cortex is laid down between the recently described (5) double layers of the forespore membrane. Then when the cortex is ⅓ fully formed, the spore coat and exosporium are laid down peripheral to the outer membrane layer covering the cortex. As these latter layers appear, the spores, previously dense by dark phase contrast, gradually "whiten" or show an increase in refractive index. With this whitening, calcium uptake commences, closely followed by the synthesis of dipicolinic acid and the process is terminated, an hour later, with the formation of a fully refractile spore. In calcium-deficient media, final refractility is lessened and dipicolinic acid is formed only in amounts proportional to the available calcium. If calcium is withheld during the period of uptake beyond a critical point, sporulating cells lose the ability to assimilate calcium and to form normal amounts of dipicolinic acid. The resulting deficient spores are liberated from the sporangia but are unstable in water suspensions. Unlike ripe spores, they do not react violently to acid hydrolysis and, in thin sections, their cytoplasmic granules continue to stain with lead solutions.

scholarly journals Chemical and Morphological Studies of Bacterial Spore Formation

1959 ◽  
Vol 6 (3) ◽  
pp. 467-482 ◽  
Author(s):  
I. Elizabeth Young ◽  
Philip C. Fitz-James
Keyword(s):  
Deoxyribonucleic Acid ◽  
Growth Cycle ◽  
Dark Phase ◽  
Experimental Conditions ◽  
Radioactive Phosphorus ◽  
Thin Sections ◽  
Morphological Studies ◽  
Segregation Process ◽  
A Cell ◽  
Bright Field Microscopy

Experimental conditions were developed whereby a culture of Bacillus cereus formed spores with reasonable synchrony following a growth cycle of some 8 hours. The cytology of this metamorphosis was studied by dark phase contrast, bright-field microscopy and electron microscopy of thin sections. Particular attention has been paid to the changes in chromatin patterns and these have been correlated with quantitative chemical estimations of the nucleic acids. The cell commencing sporulation contains two compact chromatin bodies and twice the spore amount of deoxyribonucleic acid. Following fusion of the two chromatin bodies, one-half of this chromatin becomes located at a cell end. A transverse septum growing inwards from, and remaining attached to, the inner surface of the cell wall separates this end-piece of chromatin and some associated cytoplasm from the rest of the cell to form the primordial spore. Although the synthesis of deoxyribonucleic acid ceases during the segregation process, it recommences in this organism and continues at a linear rate as the spore develops. Tracer studies with radioactive phosphorus indicated that this further synthesis is confined to the non-spore portion of the sporangium. Although the net synthesis of ribonucleic acid ceased prior to the onset of sporogenesis, some evidence of a turnover of this fraction during the sporulation process was found.

A Simple Method for Phase-contrast Microscopy: Improvements in Technique

1949 ◽  
Vol s3-90 (11) ◽  
pp. 323-329
Author(s):  
JOHN R. BAKER ◽  
D. A. KEMPSON ◽  
P.C. J. BRUNET
Keyword(s):  
Phase Contrast ◽  
Magnesium Fluoride ◽  
Phase Plate ◽  
Dark Phase ◽  
Phase Contrast Microscopy ◽  
Simple Method ◽  
Contrast Microscopy ◽  
Bull's Eye ◽  
Made In

The following are the main improvements that we have made in the method of phase-contrast microscopy described by Kempson, Thomas, and Baker (1948): 1. No bull's-eye condenser is used. The illuminant is an electric bulb with a ‘porcelain-processed’, ‘flashed white’, or ‘opal’ surface. 2. No oiled paper is placed over the illuminating annulus. 3. The thickness of the deposit of magnesium fluoride on the phase-plate is controlled by observations on the interference colours given by surface reflections. 4. Positive (dark) phase-contrast is preferred for most purposes to negative (bright).

Histochemical and Morphological Studies of Lipids in the Oogenesis of Pheretima posthuma

1958 ◽  
Vol s3-99 (48) ◽  
pp. 475-484
Author(s):  
VISHWA NATH ◽  
BRIJ L. GUPTA ◽  
S. L. MANOCHA
Keyword(s):  
Phase Contrast ◽  
Chemical Change ◽  
Follicular Epithelium ◽  
Cholesteryl Esters ◽  
Lipid Bodies ◽  
Interference Microscope ◽  
Phase Contrast Microscope ◽  
Morphological Studies ◽  
Contrast Microscope ◽  
Second Category

A study of the oocytes of the earthworm, Pheretima posthuma, examined fresh under the phase-contrast and interference microscopes as well as by histochemical techniques, has revealed that there are two types of lipid bodies in the cytoplasm. The lipid bodies of the first type (L1) are smaller, appear as homogeneous, dark granules under the phase-contrast microscope, and have a protein-phospholipid core surrounded by a thick sheath of phospholipids only. The lipid bodies of the second category (L2), which arise as a result of growth and chemical change in L1 bodies, have a pure phospholipid core surrounded by a thick triglyceride sheath. They give a ringed appearance under the phase-contrast microscope. The study under the interference microscope shows that this ringed appearance is an optical artifact. The lipid spheres present in the follicular epithelium contain phospholipids only. The mitochondria are in the form of minute granules. They remain unchanged throughout oogenesis. Some vacuoles devoid of any lipids, proteins, or carbohydrates have been observed. They also remain unchanged. Pure triglyceride spheres, yolk globules, nucleolar extrusions, as well as cholesterols and cholesteryl esters are absent.

scholarly journals Catatropis pakistanensis n. sp. (Trematoda: Notocotylidae) from Northern shovelers, Anas clypeata (Anatidae: Aves) from Pakistan with some remarks on the history of Catatropis species

2012 ◽  
Vol 49 (1) ◽  
pp. 43-48 ◽  
Author(s):  
R. Schuster ◽  
G. Wibbelt
Keyword(s):  
Electron Microscopy ◽  
Histological Evaluation ◽  
Thin Sections ◽  
Genital Opening ◽  
Morphological Studies ◽  
Anas Clypeata ◽  
History Of ◽  
Free Ranging ◽  
A New Species ◽  
Scanning Electron

AbstractFive out of 15 free-ranging Northern shovelers (Anas clypeata Linneus) caught in Pakistan were infected with notocotylid trematodes. Out of the 31 flukes, 10 specimens were used morphological studies, 4 others were also examined by scanning electron microscopy and one remaining trematode was cut in serial semi-thin sections for histological evaluation in order to describe a new species. Like all species of this genus, Catatropis pakistanensis n. sp has a median ridge starting posterior to the basis of the cirrus sac and extends posterior to the ovary. Bilateral to this ridge there are two rows of 9–10 ventral papillae each. Metraterm and cirrus sac are equally in length. In contrast to most other Catatropis spp. the genital opening in C. pakistanensis is situated between the oral sucker and bifurcation of the caeca.

scholarly journals STUDIES ON THE MODE OF ACTION OF EXCESS OF VITAMIN A

1963 ◽  
Vol 17 (1) ◽  
pp. 111-121 ◽  
Author(s):  
Audrey M. Glauert ◽  
Mary R. Daniel ◽  
J. A. Lucy ◽  
J. T. Dingle
Keyword(s):  
Electron Microscopy ◽  
Fine Structure ◽  
Vitamin A ◽  
Phase Contrast ◽  
Phase Contrast Microscopy ◽  
Intact Cells ◽  
Thin Sections ◽  
Initial Effect ◽  
Contrast Microscopy ◽  
Site Of Action

Rabbit erythrocytes have been haemolysed by treatment with vitamin A alcohol and the sequence of changes in the fine structure of the cells during lysis has been investigated by phase contrast microscopy of intact cells and electron microscopy of thin sections. The initial effect of the vitamin, which occurs within 1 minute, is the production of cells of bizarre appearance which have a greatly increased surface area relative to untreated cells. Large indentations appear in the surfaces of the cells, and vacuoles are formed from the indentations by a process that resembles micropinocytosis. The cells then become spherical and loss of haemoglobin begins as breaks appear in the membranes of some cells; finally, ghosts are produced that are no longer spherical but still contain numerous vacuoles. These observations support the thesis that one site of action of vitamin A is at lipoprotein membranes.

Pollen morphology of Ginkgo biloba and Cycas revoluta

1986 ◽  
Vol 64 (12) ◽  
pp. 3075-3078 ◽  
Author(s):  
N. Sahashi ◽  
J. Ueno
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Ginkgo Biloba ◽  
Pollen Morphology ◽  
Pollen Grains ◽  
Spherical Form ◽  
Thin Sections ◽  
Morphological Studies ◽  
Cycas Revoluta ◽  
Scanning Electron

Morphological studies on pollen grains of Ginkgo biloba L. and Cycas revoluta Thunb. were carried out by scanning electron microscopy. The pollen grains of both species are generally oblong with 1-sulcate apertures which are shrunken as a result of dryness. However, the swollen grains show an almost spherical form with a large and rounded germinal aperture. This aperture may not correspond to any aperture type so far known, although the term "anaporate" can be fitted to the swollen pollen grains. Auricular projections, which may be derived from protrusions of the ectosexine, can be seen sometimes on the surface of the pollen grains. These projections remind us of degraded versions of the bladders that may have been present on the pollen grains of the fossil ancestor. The inner side of the exine, which can be seen in thin sections obtained with the freezing microtome, is ornamented with reticulumlike sculptures. These endosculptures may be the first reported among gymnosperm pollen grains.

scholarly journals ULTRASTRUCTURE AND CALCIUM TRANSPORT IN CRUSTACEAN MUSCLE MICROSOMES

1971 ◽  
Vol 48 (1) ◽  
pp. 49-60 ◽  
Author(s):  
R. J. Baskin
Keyword(s):  
Freeze Drying ◽  
Calcium Uptake ◽  
Membrane Thickness ◽  
Electron Microscopic ◽  
Thin Sections ◽  
Crustacean Muscle ◽  
Thin Sectioning ◽  
Critical Point Drying ◽  
Freeze Etching ◽  
Microscopic Techniques

Fragmented sarcoplasmic reticulum (FSR) from crustacean muscle was examined following preparation by a variety of electron microscopic techniques. The 30–40 A particles which appeared on the outer surface of FSR vesicles following negative staining were not observed following preparation by freeze-drying, freeze-etching, thin sectioning, or critical-point drying. Crustacean FSR exhibited high values of calcium uptake and extensive nodular formation in the presence of oxalate. 80–90 A diameter membrane particles were seen in freeze-etch preparations of both intact lobster muscle and FSR vesicles. Thin sections of FSR vesicles revealed a membrane thickness of 60–70 A. The membrane appeared to be triple layered, each layer having a thickness of 20–25 A.

Acute effects of ethane dimethane sulfonate (EDS) on the structure of the cauda epididymidis in the rat: selective destruction of clear cells in the proximal cauda region

1993 ◽  
Vol 5 (3) ◽  
pp. 295 ◽  
Author(s):  
X Liu ◽  
PD Temple-Smith ◽  
GP Risbridger
Keyword(s):  
Structural Changes ◽  
Control Group ◽  
Electron Microscopic ◽  
Cell Degeneration ◽  
Vascular Perfusion ◽  
Thin Sections ◽  
Clear Cells ◽  
Selective Destruction ◽  
Morphological Studies ◽  
Cauda Epididymidis

Of eight groups of five adult male Sprague-Dawley rats, three groups received an intraperitoneal dose of EDS (75 mg kg-1) in DMSO (dimethylsulfoxide in water; 1:3) and three control groups received DMSO only. One EDS and one control group were killed 1, 2 and 3 days after treatment. One EDS+T group, given a 5-cm implant of T sufficient to maintain normal serum T concentrations, and one untreated control group were killed on Day 3. Epididymides were fixed by vascular perfusion and embedded in Epon/Araldite for light and electron microscopic studies. Epididymal duct diameters and epithelial heights were measured from 1-micron sections and structural changes were assessed from thin sections using a Jeol 100B electron microscope. Morphological studies showed a reduction in duct diameter and an associated increase in epithelial height in the proximal cauda epididymidis of the experimental groups. In the EDS+T implant group, epithelial heights were significantly greater than in controls but duct diameters remained unchanged. The most obvious structural change in the proximal cauda epididymidis was the selective destruction of clear cells in the epithelium. Initially, vacuoles were observed in the lateral intercellular spaces of the epithelium; large autophagic vacuoles then appeared in the clear cells, which had degenerated and disappeared from the epithelium by Day 3. Progressive infiltration of leucocytes into the intertubular interstitium, the epithelium and lumen of the proximal cauda was also observed. Loss of clear cells in the proximal cauda epididymidis was also seen in the EDS+T group, suggesting that clear-cell degeneration was not associated with reduced concentrations of circulating androgen. In all EDS-treated groups, however, clear cells and duct profiles in the distal cauda epididymidis remained unaffected. The reason for their protection from the effects of EDS has not yet been determined. These results suggest that, in addition to other specific lesions described in previous studies, EDS also has a direct effect on the rat epididymis that appears to be specifically targeted to the clear cells in the proximal caudal region.

Origin of rigid bacterial "giant flagella" ("giant whips", riesenzopfe)

1968 ◽  
Vol 14 (9) ◽  
pp. 941-947 ◽  
Author(s):  
Michael E. Frank ◽  
Heiner Hoffman
Keyword(s):  
Escherichia Coli ◽  
Life History ◽  
Phase Contrast ◽  
Dark Field ◽  
Coli Strain ◽  
Bacillus Species ◽  
Dark Phase ◽  
Active Period ◽  
Proteus Vulgaris ◽  
Motile Cells

Development of "giant flagella" in microcultures of Proteus vulgaris occurred by an aggregation of flagella from motionless cells in a microcolony. Regular free flagellar aggregations very similar to those of the Proteus also were encountered in microcultures of a peritrichous Bacillus species, but were seen in but one of a very large number of microcultures of a monotrichous Escherichia coli strain. Observation of actively motile cells in wet mounts and of stained preparations of the three species with dark phase contrast, Nomarski differential interference, dark-field, and brightfield optics led to an hypothesis concerning the life history which accepts the flagellum as being flexible in the functional state. After an active period extending through more than one generation, the flagellum becomes rigid and apparently is ejected from the cell as a complete unit, including what appears to be a bulbous basal body.

scholarly journals A Polysaccharide Deacetylase Gene (pdaA) Is Required for Germination and for Production of Muramic δ-Lactam Residues in the Spore Cortex of Bacillus subtilis

2002 ◽  
Vol 184 (21) ◽  
pp. 6007-6015 ◽  
Author(s):  
Tatsuya Fukushima ◽  
Hiroki Yamamoto ◽  
Abdelmadjid Atrih ◽  
Simon J. Foster ◽  
Junichi Sekiguchi
Keyword(s):  
Bacillus Subtilis ◽  
Phase Contrast ◽  
Biosynthetic Pathway ◽  
Wild Type Strain ◽  
Dipicolinic Acid ◽  
Northern Hybridization ◽  
Predicted Amino Acid Sequence ◽  
Wild Type ◽  
Contrast Microscopy ◽  
Acid Release

ABSTRACT The predicted amino acid sequence of Bacillus subtilis yfjS (renamed pdaA) exhibits high similarity to those of several polysaccharide deacetylases. β-Galactosidase fusion experiments and results of Northern hybridization with sporulation sigma mutants indicated that the pdaA gene is transcribed by EσG RNA polymerase. pdaA-deficient spores were bright by phase-contrast microscopy, and the spores were induced to germination on the addition of l-alanine. Germination-associated spore darkening, a slow and partial decrease in absorbance, and slightly lower dipicolinic acid release compared with that by the wild-type strain were observed. In particular, the release of hexosamine-containing materials was lacking in the pdaA mutant. Muropeptide analysis indicated that the pdaA-deficient spores completely lacked muramic δ-lactam. A pdaA-gfp fusion protein constructed in strain 168 and pdaA-deficient strains indicated that the protein is localized in B. subtilis spores. The biosynthetic pathway of muramic δ-lactam is discussed.

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