scholarly journals Further Observations on the ‘Metaplasia’ of an Amoeba, Naegleria gruberi

Development ◽  
1958 ◽  
Vol 6 (2) ◽  
pp. 187-214
Author(s):  
E. N. Willmer
Keyword(s):  
Turning Points ◽  
External Environment ◽  
Distilled Water ◽  
Ionic Balance ◽  
Critical Concentrations ◽  
Amoeboid Form ◽  
Simple Movement ◽  
Naegleria Gruberi

The development of flagella by Naegleria gruberi, which occurs when a culture of organisms in the amoeboid form is treated with distilled water, has been shown (Willmer, 1956) to be a phenomenon probably related more to the ionic balance between the organism and its external environment than to the simple movement of water in and out of the cell in response to total osmotic changes. From Text-fig. 1 it may be seen that with respect to the response of the amoeba to different concentrations of the various salts investigated there are for each salt two somewhat critical concentrations. In the case of NaCl solutions in distilled water these turning points occur at about 30 mM. and 1 mM., and in the case of KCl solutions at about 50 mM. and 6 mM. Above the higher of these concentrations in each case the organisms always assume the amoeboid form, and below the lower they become flagellate at least as frequently as they do in distilled water.

scholarly journals Factors Which Influence the Acquisition of Flagella by the Amoeba, Naegleria Gruberi

1956 ◽  
Vol 33 (3) ◽  
pp. 583-603
Author(s):  
E. N. WILLMER
Keyword(s):  
Sodium Bicarbonate ◽  
Sodium Phosphate ◽  
Sodium Lactate ◽  
Lithium Salts ◽  
Distilled Water ◽  
Free Swimming ◽  
Low Concentrations ◽  
Amoeboid Form ◽  
Optimum Ph ◽  
Naegleria Gruberi

1. When placed in distilled water Naegleria gruberi changes from an amoeboid organism, with little evidence of polarity, to a highly polarized free-swimming flagellate. The details of this metamorphosis are described. The change is reversible. 2. Alteration of osmotic pressure is not in itself the direct cause of the metamorphosis, though the loss of certain ions is clearly important. 3. The metamorphosis is favoured by the presence of low concentrations (less than M/80) of sodium bicarbonate, sodium lactate and sodium phosphate. 4. The flagellate form probably occurs most frequently in conditions of neutrality; but, in the presence of phosphate, acid conditions tend to be more favourable to the flagellate form, while in the presence of bicarbonate the optimum pH is nearer pH 8.0. 5. The metamorphosis to the flagellate form is suppressed by a variety of agents including lithium salts, magnesium chloride and the sulphate ion under some conditions. These all act at concentrations which leave the amoeboid form in full activity. In some cases their action is decreased by the presence of bicarbonate in the medium.

scholarly journals Osmotic Blistering in Enamel Bonded with One-step Self-etch Adhesives

2004 ◽  
Vol 83 (4) ◽  
pp. 290-295 ◽  
Author(s):  
F.R. Tay ◽  
C.N.S. Lai ◽  
S. Chersoni ◽  
D.H. Pashley ◽  
Y.F. Mak ◽  
...  
Keyword(s):  
Field Emission ◽  
Water Permeability ◽  
Water Sorption ◽  
External Environment ◽  
Osmotic Gradient ◽  
Distilled Water ◽  
Tooth Surfaces ◽  
One Step ◽  
Self Etch ◽  
Environmental Sem

One-step self-etch adhesives behave as permeable membranes after polymerization, permitting water to move through the cured adhesives. We hypothesize that osmotic blistering occurs in bonded enamel when these adhesives are used without composite coupling. Tooth surfaces from extracted human premolars were bonded with 5 one-step self-etch adhesives. They were immersed in distilled water or 4.8 M CaCl2, and examined by stereomicroscopy, field-emission/environmental SEM, and TEM. Water blisters were observed in bonded enamel but not in bonded dentin when specimens were immersed in water. They collapsed when water was subsequently replaced with CaCl2. Blisters were absent from enamel in specimens that were immersed in CaCl2 only. Water trees were identified from adhesive-enamel interfaces. Osmotic blistering in enamel is probably caused by the low water permeability of enamel. This creates an osmotic gradient between the bonded enamel and the external environment, causing water sorption into the interface.

Some Observations on the Actions of Steroids on the Metaplasia of the Amoeba, Naegleria Gruberi

1963 ◽  
Vol 40 (3) ◽  
pp. 493-516
Author(s):  
JANET L. PEARSON ◽  
E. N. WILLMER
Keyword(s):  
Human Body ◽  
Dose Response ◽  
The Other ◽  
Great Decrease ◽  
Response Curves ◽  
Buffer Solution ◽  
Buffer Solutions ◽  
Amoeboid Form ◽  
High Concentrations ◽  
Naegleria Gruberi

1. The age of the culture of Naegleria gruberi, i.e. the time since the last subculture, is of little importance in determining the numbers of cells which turn flagellate when placed in the extremely dilute buffer solutions used. 2. Between 17° and 21° C. there is a very great decrease in the time which the amoebae require in order to become flagellate when placed in buffer solution. 3. There is no evidence that the amoeba, as such, differentiates between solutions of KC1 or NaCl. On the other hand, the flagellate form is somewhat more reactive to KC1 than to NaCl, and fewer flagellates are found in KC1 solutions. 4. The metaplasia is affected by the presence of steroids in the medium. 5. The more interesting actions of the steroids tested may be summarized as follows. At high concentrations, progesterone and deoxycorticosterone, when applied to the amoeba, prevent the change to the flagellate form. When applied to the flagellate, progesterone has little action, but deoxycorticosterone encourages the return to the amoeboid form, especially in the presence of K+. In lower concentrations both steroids favour the change from amoeba to flagellate and also from flagellate to amoeba. Other steroids have characteristic effects. 6. While the dose/response curves indicate qualitatively different effects of concentration of progesterone and deoxycorticosterone they only show quantitatively different effects with oestradiol and androsterone. 7. Progesterone acts on amoebae at concentrations which are comparable with those at which it acts in the human body. 8. When both progesterone and oestradiol are applied together at concentrations which suppress the flagellate form the effects are additive. The same applies to mixtures of testosterone and oestradiol. An activating concentration of progesterone has not yet been tested in combination with an inhibiting dose of oestradiol.

Biophysical Measurement of Molecular Weight of Foot-and-Mouth Disease RNA Fragments

1974 ◽  
Vol 32 ◽  
pp. 262-263
Author(s):  
Sydney S. Breese ◽  
Howard L. Bachrach
Keyword(s):  
Chemical Properties ◽  
Foot And Mouth Disease ◽  
Mouth Disease ◽  
Distilled Water ◽  
Bovine Plasma ◽  
Mouth Disease Virus ◽  
Foot And Mouth ◽  
Carbon Coated ◽  
Rna Fragments ◽  
Physical And Chemical

Continuing studies on the physical and chemical properties of foot-and-mouth disease virus (FMDV) have included electron microscopy of RNA strands released when highly purified virus (1) was dialyzed against demlneralized distilled water. The RNA strands were dried on formvar-carbon coated electron microscope screens pretreated with 0.1% bovine plasma albumin in distilled water. At this low salt concentration the RNA strands were extended and were stained with 1% phosphotungstic acid. Random dispersions of strands were recorded on electron micrographs, enlarged to 30,000 or 40,000 X and the lengths measured with a map-measuring wheel. Figure 1 is a typical micrograph and Fig. 2 shows the distributions of strand lengths for the three major types of FMDV (A119 of 6/9/72; C3-Rezende of 1/5/73; and O1-Brugge of 8/24/73.

Freeze-fracture, freeze-etch complementary pairs of virus-infected cells reveal value of etching even when relatively high concentrations of cryoprotectants are used

1978 ◽  
Vol 36 (2) ◽  
pp. 136-137
Author(s):  
Russell L. Steere ◽  
Eric F. Erbe
Keyword(s):  
Plant Tissue ◽  
Phosphate Buffer ◽  
Infected Plant ◽  
Freeze Fracture ◽  
Distilled Water ◽  
Virus Infected Plant ◽  
Infected Cells ◽  
High Concentrations

It has been assumed by many involved in freeze-etch or freeze-fracture studies that it would be useless to etch specimens which were cryoprotected by more than 15% glycerol. We presumed that the amount of cryoprotective material exposed at the surface would serve as a contaminating layer and prevent the visualization of fine details. Recent unexpected freeze-etch results indicated that it would be useful to compare complementary replicas in which one-half of the frozen-fractured specimen would be shadowed and replicated immediately after fracturing whereas the complement would be etched at -98°C for 1 to 10 minutes before being shadowed and replicated.Standard complementary replica holders (Steere, 1973) with hinges removed were used for this study. Specimens consisting of unfixed virus-infected plant tissue infiltrated with 0.05 M phosphate buffer or distilled water were used without cryoprotectant. Some were permitted to settle through gradients to the desired concentrations of different cryoprotectants.

Comparison of Acrylamide and Agar Gels by Freeze-Etching

1977 ◽  
Vol 35 ◽  
pp. 606-607
Author(s):  
Russell L. Steere ◽  
Eric F. Erbe
Keyword(s):  
Electron Microscope ◽  
Sodium Hydroxide ◽  
Sodium Hypochlorite ◽  
Chromic Acid ◽  
Distilled Water ◽  
Thin Sheets ◽  
Acid Cleaning ◽  
Agar Gels ◽  
Freeze Etching ◽  
Water Cut

Thin sheets of acrylamide and agar gels of different concentrations were prepared and washed in distilled water, cut into pieces of appropriate size to fit into complementary freeze-etch specimen holders (1) and rapidly frozen. Freeze-etching was accomplished in a modified Denton DFE-2 freeze-etch unit on a DV-503 vacuum evaporator.* All samples were etched for 10 min. at -98°C then re-cooled to -150°C for deposition of Pt-C shadow- and C replica-films. Acrylamide gels were dissolved in Chlorox (5.251 sodium hypochlorite) containing 101 sodium hydroxide, whereas agar gels dissolved rapidly in the commonly used chromic acid cleaning solutions. Replicas were picked up on grids with thin Foimvar support films and stereo electron micrographs were obtained with a JEM-100 B electron microscope equipped with a 60° goniometer stage.Characteristic differences between gels of different concentrations (Figs. 1 and 2) were sufficiently pronounced to convince us that the structures observed are real and not the result of freezing artifacts.

Heterogeneity of Size and Distribution of Intramembrane Particles in the Plasma Membrane of Yeast

1977 ◽  
Vol 35 ◽  
pp. 596-597
Author(s):  
E. Keyhani
Keyword(s):  
Plasma Membrane ◽  
Candida Utilis ◽  
Synthetic Medium ◽  
Freeze Fracture ◽  
Translational Diffusion ◽  
Yeast Cells ◽  
Distilled Water ◽  
Intramembrane Particles ◽  
The Matrix ◽  
Water Cell

The matrix of biological membranes consists of a lipid bilayer into which proteins or protein aggregates are intercalated. Freeze-fracture techni- ques permit these proteins, perhaps in association with lipids, to be visualized in the hydrophobic regions of the membrane. Thus, numerous intramembrane particles (IMP) have been found on the fracture faces of membranes from a wide variety of cells (1-3). A recognized property of IMP is their tendency to form aggregates in response to changes in experi- mental conditions (4,5), perhaps as a result of translational diffusion through the viscous plane of the membrane. The purpose of this communica- tion is to describe the distribution and size of IMP in the plasma membrane of yeast (Candida utilis).Yeast cells (ATCC 8205) were grown in synthetic medium (6), and then harvested after 16 hours of culture, and washed twice in distilled water. Cell pellets were suspended in growth medium supplemented with 30% glycerol and incubated for 30 minutes at 0°C, centrifuged, and prepared for freeze-fracture, as described earlier (2,3).

Advances in Microprobe Analysis Applied to Muscle, Nerve and Gland

1982 ◽  
Vol 40 ◽  
pp. 404-407
Author(s):  
T. E. Hutchinson ◽  
D. E. Johnson ◽  
A. C. Lee ◽  
E. Y. Wang
Keyword(s):  
Biological Tissue ◽  
Microprobe Analysis ◽  
Physiological State ◽  
External Environment ◽  
Physiological Relevance ◽  
Muscle Nerve ◽  
Technique Development

Microprobe analysis of biological tissue is now in the end phase of transition from instrumental and technique development to applications pertinent to questions of physiological relevance. The promise,implicit in early investigative efforts, is being fulfilled to an extent much greater than many had predicted. It would thus seem appropriate to briefly report studies exemplifying this, ∿. In general, the distributions of ions in tissue in a preselected physiological state produced by variations in the external environment is of importance in elucidating the mechanisms of exchange and regulation of these ions.

Microanatomy of the Periplasm of Bacillus Licheniformis

1971 ◽  
Vol 29 ◽  
pp. 262-263
Author(s):  
B.K. Ghosh
Keyword(s):  
Cell Wall ◽  
Plasma Membrane ◽  
Bacillus Licheniformis ◽  
External Environment ◽  
Permeability Barrier ◽  
Periplasmic Space ◽  
Modified Technique ◽  
Gram Positive ◽  
Gram Negative ◽  
Gram Positive Bacteria

Periplasm of bacteria is the space outside the permeability barrier of plasma membrane but enclosed by the cell wall. The contents of this special milieu exterior could be regulated by the plasma membrane from the internal, and by the cell wall from the external environment of the cell. Unlike the gram-negative organism, the presence of this space in gram-positive bacteria is still controversial because it cannot be clearly demonstrated. We have shown the importance of some periplasmic bodies in the secretion of penicillinase from Bacillus licheniformis.In negatively stained specimens prepared by a modified technique (Figs. 1 and 2), periplasmic space (PS) contained two kinds of structures: (i) fibrils (F, 100 Å) running perpendicular to the cell wall from the protoplast and (ii) an array of vesicles of various sizes (V), which seem to have evaginated from the protoplast.

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