An experimental approach to the development of the ear capsule in the turtle, Chelydra serpentina

Development ◽  
1965 ◽  
Vol 13 (2) ◽  
pp. 141-149
Author(s):  
M. J. Toerien
Keyword(s):  
Recent Work ◽  
Experimental Approach ◽  
Experimental Studies ◽  
Chelydra Serpentina ◽  
Medial Aspect ◽  
Early Stages ◽  
Otic Placode ◽  
Auditory Region

The effects of the elimination of the otic placode or otocyst on the development of the cartilaginous ear capsule and columella auris have been observed in several fishes, amphibians and birds and are summarized by de Beer (1937), Yntema (1955) and Benoit (1957). More recent work includes that of Benoit (1960) and Toerien (1963). Except in the fish Acipenser (Filatow, 1930) the development of a cartilaginous ear capsule is completely suppressed following the removal of the otocyst. The effect of the operation on the development of the columella is not so clear and the resultant deficiency in the medial aspect has been interpreted in various ways. Yntema's (1965) method for using turtle eggs has made the early stages of reptilian embryos available for experimental studies. The purpose of the present investigation, therefore, is to study the effect of the removal of the placode on the development of the auditory region in yet another vertebrate class

scholarly journals Solvent-mediated Isotope Effects Strongly Influence the Early Stages of Calcium Carbonate Formation: Exploring D2O vs. H2O in a Combined Computational and Experimental Approach

2021 ◽  
Author(s):  
Michael King ◽  
Jonathan Thomas Avaro ◽  
Christine Peter ◽  
Karin Hauser ◽  
Denis Gebauer
Keyword(s):  
Calcium Carbonate ◽  
Heavy Water ◽  
Experimental Approach ◽  
Isotope Effects ◽  
Experimental Studies ◽  
Reaction Pathways ◽  
Solvent Exchange ◽  
Early Stages ◽  
Carbonate Formation

In experimental studies, heavy water (D2O) is employed, e.g., so as to shift the spectroscopic solvent background, but any potential effects of this solvent exchange on reaction pathways are often...

An Experimental Approach to the Function of Classic Maya Chultuns

1971 ◽  
Vol 36 (3) ◽  
pp. 322-335 ◽  
Author(s):  
Dennis E. Puleston
Keyword(s):  
Experimental Approach ◽  
Experimental Studies ◽  
Water Storage ◽  
Food Storage ◽  
Food Crop ◽  
Traditional Foods ◽  
Long Term Storage ◽  
Brosimum Alicastrum ◽  
Term Storage

AbstractExperimental techniques have provided an exciting breakthrough for the functional analysis of Maya chultuns. While deep cistern-like chultuns, common at certain sites in the northern lowlands, have been shown to be functional for water storage, smaller lateral-chambered chultuns characteristic of certain parts of the southern lowlands probably had a very different function. Excavation and examination of the latter features, in light of a whole range of possibilities, suggest that they were constructed to be used for food storage. Experimental studies, however, reveal them to be unsuitable for the storage of most traditional foods, including maize. At least one local food crop, the seed of the ramon (Brosimum alicastrum, Moraceae), appears to be ideally suited for long-term storage under these conditions. Chambers constructed beneath platforms in the northern lowlands may have been used for the storage of maize. A need for more experimental work is indicated.

scholarly journals Mechanisms of aortic valve calcification: the LDL-density-radius theory: a translation from cell signaling to physiology

2010 ◽  
Vol 298 (1) ◽  
pp. H5-H15 ◽  
Author(s):  
Nalini M. Rajamannan
Keyword(s):  
Risk Factors ◽  
Severe Aortic Stenosis ◽  
Elevated Serum ◽  
Experimental Studies ◽  
Atherosclerotic Lesion ◽  
Disease Process ◽  
Prognostic Indicator ◽  
Epidemiologic Studies ◽  
Factors Associated ◽  
Early Stages

Recent epidemiologic studies have revealed the risk factors associated for vascular atherosclerosis, including the male sex, smoking, hypertension, and elevated serum cholesterol, similar to the risk factors associated with the development of AV stenosis. An increasing number of models of experimental hypercholesterolemia demonstrate features of atherosclerosis in the AV, which are similar to the early stages of vascular atherosclerotic lesions. Experimental and clinical studies demonstrate that the hypercholesterolemic AV develops an atherosclerotic lesion which is proliferative and expresses high levels of osteoblast bone markers which mineralize over time to form bone. Calcification, the end-stage process of the disease, is necessary to understand as a prognostic indicator in the modification of this cellular process before it is too late. In summary, these findings suggest that medical therapies may have a potential role in patients in the early stages of this disease process to slow the progression to severe aortic stenosis and to delay the timing of the need for surgery. The translation of these experimental studies to clinical practice will be important to understand the potential for medical therapy for this disease process.

Material Properties Over-Estimated by Boundary Conditions in Biaxial Tension Can Be Corrected Using Finite Element Analysis

2012 ◽  
Author(s):  
Nathan T. Jacobs ◽  
Daniel H. Cortes ◽  
Spencer E. Szczesny ◽  
Edward J. Vresilovic ◽  
Dawn M. Elliott
Keyword(s):  
Material Properties ◽  
Experimental Approach ◽  
Soft Tissues ◽  
Biaxial Tension ◽  
Experimental Studies ◽  
Constitutive Relationship ◽  
Element Analysis ◽  
Tissue Modeling ◽  
In Situ Conditions

Tissue modeling requires an appropriate stress-strain constitutive relationship and a corresponding set of material properties. It is often the goal of experimental studies to determine these material properties. Uniaxial tension experiments are simple in experimental approach and the interpretation of results is straightforward, prompting its use in several studies. However, the freely contracting lateral edges observed in this loading modality do not mimic the in situ conditions of many fiber-reinforced soft tissues and the unconstrained fibers may also create errors.

Non-planar Boron Lewis Acids Taking the Next Step: Development of Tunable Lewis Acids, Lewis Superacids and Bifunctional Catalysts

Synlett ◽  
2020 ◽  
Vol 31 (17) ◽  
pp. 1639-1648
Author(s):  
Guillaume Berionni ◽  
Aurélien Chardon ◽  
Arnaud Osi ◽  
Damien Mahaut ◽  
Ali Ben Saida
Keyword(s):  
Recent Work ◽  
Research Group ◽  
Lewis Acids ◽  
Experimental Studies ◽  
Planar Geometry ◽  
Bifunctional Catalysts ◽  
Group 13 ◽  
Recent Developments ◽  
Stereoelectronic Properties ◽  
Planar Group

Although boron Lewis acids commonly adopt a trigonal planar geometry, a number of compounds in which the trivalent boron atom is located in a pyramidal environment have been described. This review will highlight the recent developments of the chemistry and applications of non-planar boron Lewis acids, including a series of non-planar triarylboranes derived from the triptycene core. A thorough analysis of the properties and of the influence of the pyramidalization of boron Lewis acids on their stereoelectronic properties and reactivities is presented based on recent theoretical and experimental studies.1 Non-planar Trialkylboranes2 Non-planar Alkyl and Aryl-Boronates3 Non-planar Triarylboranes and Alkenylboranes3.1 Previous Investigations on Bora Barrelenes and Triptycenes3.2 Recent Work on Boratriptycenes from Our Research Group4 Applications of Non-planar Boranes4.1 Non-planar Alkyl Boranes and Boronates4.2 Non-planar Triarylboranes (Boratriptycenes)5 Other Non-planar Group 13 Lewis Acids6 Further Work and Perspectives

scholarly journals Condensing osteitis of the clavicle

1996 ◽  
Vol 1 (2) ◽  
pp. 24-27
Author(s):  
G. C. Ooi ◽  
W. C.G Peh
Keyword(s):  
Sternoclavicular Joint ◽  
Unknown Aetiology ◽  
Medial Aspect ◽  
Benign Condition ◽  
Radiological Features ◽  
Early Stages ◽  
Child Bearing ◽  
Condensing Osteitis

Condensing osteitis of the clavicle is a rare benign condition of unknown aetiology which afflicts women of child-bearing age. It is characterised radiologically by sclerosis of the infero-medial aspect of the clavicle, with preservation of the sternoclavicular joint in the early stages of the disease. The clinico-radiological features of this condition are discussed in this review, together with other conditions which resemble this entity.

Bound—Rubber Formation in Diene Polymer Stocks

1958 ◽  
Vol 31 (2) ◽  
pp. 369-373 ◽  
Author(s):  
P. B. Stickney ◽  
E. E. McSweeney ◽  
W. J. Mueller ◽  
S. T. Palinchak
Keyword(s):  
Particle Size ◽  
Carbon Black ◽  
Recent Work ◽  
Experimental Approach ◽  
Polymer Gel ◽  
Fine Powders ◽  
Bound Rubber ◽  
Close Relationship ◽  
Static Extraction ◽  
Rubber Filler

Abstract The phenomenon of insolubilization of rubber by carbon black has been known for at least twenty-seven years. There have been many attempts during this time to establish a relationship between insolubilization, or bound rubber formation, and reinforcement of rubber by carbon black. It was postulated, as far back as 1925, that there was a parallelism between particle size and insolubilization. This in spite of the fact that the methods available for determining particle size of very fine powders at that time were relatively crude. It was postulated at that time that there was a close relationship between the phenomena of vulcanization and reinforcement. This concept has had recurrent periods of popularity since that time. The insolubilization of rubber by carbon black, or other pigments, has been estimated by various techniques by the early investigators in the field. In more recent work, the trend has been toward a very straightforward experimental approach. Bound rubber in an uncured rubber-filler compound is usually determined by static extraction using the same apparatus and techniques used in determining the gel content of unfilled polymers. It follows that, using this method, polymer insoluble because of crosslinking, or gel, cannot be distinguished from polymer insolubilized by incorporation of fine fillers. In investigating the formation of bound rubber, therefore, the presence of gel in the polymer being used, or formation of polymer gel during processing must be taken into account.

Experimental Studies on Dibothriocephalus latus in Man

1924 ◽  
Vol 2 (4) ◽  
pp. 151-166 ◽  
Author(s):  
G. Z. L. Le Bas
Keyword(s):  
Sexual Maturity ◽  
Experimental Studies ◽  
Early Stages

1. Infection with Dibothriocephalus latus for as long a period as nine months or with as many as three worms, apart from diarrhoea in the early stages does not necessarily give rise to any symptoms which would suggest the presence of the parasite.2. In these experimental cases a definite train of symptoms, i.e., constipation for a period of one or more days followed by diarrhcua marked the onset of complete sexual maturity of the parasite.3. No appreciable anaemia was produced, nor was there a definite diminution of erythrocytes.

Morphological and experimental studies of the somitomeric organization of the segmental plate in snapping turtle embryos

Development ◽  
1984 ◽  
Vol 84 (1) ◽  
pp. 35-48
Author(s):  
David S. Packard ◽  
Stephen Meier
Keyword(s):  
Electron Microscopy ◽  
Scanning Electron Microscopy ◽  
Final Stage ◽  
Experimental Studies ◽  
The Other ◽  
Chelydra Serpentina ◽  
Microscopy Imaging ◽  
Snapping Turtle ◽  
Somite Formation ◽  
Scanning Electron

The segmental plate mesoderm of snapping turtle embryos (Chelydra serpentina) was examined with stereoscanning electron microscopy imaging. A metameric pattern was detected along the entire length of the segmental plates. This pattern consisted of a tandem sequence of mesodermal units, called somitomeres. Each somitomere was oval to cubic in shape and the processes of the constituent mesodermal cells tended to be arranged in concentric rings about the centre of the somitomere. Several experiments from a previous study (Packard, 1980b) of snapping turtle segmental plates were repeated, but, instead of culturing the explants and observing the numbers of somites that formed, the explants were fixed immediately for scanning electron microscopy and the number of somitomeres was counted. The segmental plates were found to contain an average of 6·5 ± 0·7 somitomeres, which is almost identical to the average number of somites formed by such segmental plates when cultured (6·6 ± 1·2). Furthermore, the number of somitomeres was identical in right and left explants removed from the same embryo, and the number of somitomeres was consistent regardless of the length of the segmental plate. Both of these observations are identical to those made previously for somite formation in culture. This association between numbers of somitomeres and somites strongly suggests that one gives rise to the other. Finally, it was demonstrated that for each somite formed by a segmental plate in culture, the segmental plate contained one less somitomere. This showed in a direct manner that turtle somitomeres become somites. It was concluded that the segmental plate mesoderm of snapping turtle embryos is already segmented, and that the ‘segmentation’ seen under a dissecting microscope is actually the final stage of somitomere differentiation into an epithelial somite.

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