Size determination in Hydra: The roles of growth and budding

Development ◽  
1973 ◽  
Vol 30 (1) ◽  
pp. 1-19
Author(s):  
John W. Bisbee
Keyword(s):  
Tritiated Thymidine ◽  
Growth Dynamics ◽  
Distal Portion ◽  
Effect Of Temperature ◽  
Surface Areas ◽  
Two Temperatures ◽  
Size Of Animals ◽  
The Difference ◽  
Mitotic Figures ◽  
Bud Initiation

Hydra pseudoligactis cultured at 9 °C for 3–4 weeks are one-and-a-half times larger than those cultured at 18 °C. The size of Hydra is correlated with the numbers of epitheliomuscular and digestive cells in the distal portion of the animal and with the diameters of the epithelio-muscular cells in the peduncle. Counts of mitotic figures and tritiated-thymidine-labeled nuclei and determinations of increase in mass of Hydra populations suggest that the difference caused by these temperatures does not affect mitosis. At 9 °C buds are initiated at a lower rate and take longer to develop than at 18 °C. The surface-areas of buds raised at the two temperatures are similar. Because Hydra raised at the two temperatures have similar growth dynamics, the differences in sizes of the animals cannot be due to growth rate. The observed effect of temperature on bud initiation and development is probably relevant to the increased size of animals raised at 9 °C, since these larger animals may be accumulating more cells while losing fewer to buds.

scholarly journals The effect of temperature on the viscosity of neon

1928 ◽  
Vol 119 (783) ◽  
pp. 578-590 ◽  
Keyword(s):  
Low Temperatures ◽  
Large Range ◽  
Effect Of Temperature ◽  
Theoretical Formula ◽  
Lennard Jones ◽  
Two Temperatures ◽  
The Difference ◽  
First Time ◽  
Crucial Test

The experiments described in this paper have been carried out to obtain accurate data with respect to the variation of the viscosity of neon with temperature, over a range of several hundred degrees Centigrade. This has been rendered more desirable in view of the recent publication of a new theoretical formula for the variation of viscosity of a gas with temperature by J. E. Lennard-Jones, which he has applied with conspicuous success to various gases. In the case of neon, however, it was not possible to make a test of the formula as the experimental data are so sparse, only one observer, A. O. Rankine, having made measurements upon its viscosity, and then at only two temperatures. Accordingly, as neon should provide a crucial test between Lennard-Jones’ formula and that of Sutherland, the method already applied by the author J to the case of air was suitably modified for use with a gas of which the quantity available was strictly limited and values of the viscosity obtained from 444-5° C. downwards. Owing, however, to the increase in the quantity of neon required as the temperature was reduced, it was not found possible to take observations at a temperature lower than — 78-4° C. Unfortunately, it is only at low temperatures that the difference between the two formulæ becomes marked, and hence the results obtained have not been sufficient to provide a really crucial test between them. The determination of the viscosity over a large range does, however, for the first time, provide sufficient data for a reliable comparison to be made of the molecular properties of neon, as determined from its viscosity with the values of the same properties deduced from other sources.

The neural cell cycle in the looptail (Lp ) mutant mouse

Development ◽  
1974 ◽  
Vol 32 (3) ◽  
pp. 697-705
Author(s):  
Doris B. Wilson ◽  
E. M. Center
Keyword(s):  
Cell Cycle ◽  
Early Development ◽  
Generation Time ◽  
Mutant Mouse ◽  
Tritiated Thymidine ◽  
Neural Cell ◽  
Abnormal Development ◽  
Ventricular Cells ◽  
The Difference ◽  
Mitotic Figures

The cell cycle of mesencephalic ventricular cells was studied by means of tritiated thymidine radioautography during normal and abnormal development in the looptail (Lp ) mutant mouse. The total generation time, DNA-synthetic (S), premitotic (G2), mitotic (M), and postmitotic (G1) periods were compared in looptail homozygotes (Lp/Lp ) which exhibit neural dysraphism and in their normal littermates (+ / +) at 10 and 11 days ’ gestation. Both normal and abnormal embryos showed a chronological lengthening of the generation time between the 10th and 11th day. However, the generation time in the 10-day abnormal brains was 4·5 h longer than that in normal littermates, and the difference was the result of an increase mainly in the M and G1 periods. At 11 days of gestation the generation time in the abnormal brains increased by 50 h over that of the normal brains. Since the cell cycle was actually prolonged in the defective brains, the increased numbers of mitotic figures which characterize the looptail homozygote brain during early development appear to reflect the lengthening of the mitotic period rather than increased proliferation.

scholarly journals The Respiration of some Planktonic copepods II. The Effect Of Temperature

1953 ◽  
Vol 31 (3) ◽  
pp. 447-460 ◽  
Author(s):  
D. T. Gauld ◽  
J. E. G. Raymont
Keyword(s):  
Respiratory Rate ◽  
The Body ◽  
The Other ◽  
Effect Of Temperature ◽  
Acartia Clausi ◽  
Temora Longicornis ◽  
Different Temperatures ◽  
Planktonic Copepods ◽  
The Difference ◽  
The Relationship

The respiratory rates of three species of planktonic copepods, Acartia clausi, Centropages hamatus and Temora longicornis, were measured at four different temperatures.The relationship between respiratory rate and temperature was found to be similar to that previously found for Calanus, although the slope of the curves differed in the different species.The observations on Centropages at 13 and 170 C. can be divided into two groups and it is suggested that the differences are due to the use of copepods from two different generations.The relationship between the respiratory rates and lengths of Acartia and Centropages agreed very well with that previously found for other species. That for Temora was rather different: the difference is probably due to the distinct difference in the shape of the body of Temora from those of the other species.The application of these measurements to estimates of the food requirements of the copepods is discussed.

Note on the effect of temperature on a mixed culture of two organisms in symbiotic relation

1939 ◽  
Vol 29 (2) ◽  
pp. 302-305 ◽  
Author(s):  
E. H. Richards
Keyword(s):  
Nitrogen Fixation ◽  
Mixed Culture ◽  
Azotobacter Chroococcum ◽  
Mixed Cultures ◽  
Effect Of Temperature ◽  
Two Temperatures ◽  
Symbiotic Relation

1. A study was made of nitrogen-fixation byAzotobacter chroococcumalone in a medium containing dextrose (which it can utilize) and in mixture with a coliform organism on a medium containing no carbohydrate except starch, whichAzotobactercannot utilize unless it be hydrolysed by the coliform organism or some other agency.2. The amount of nitrogen fixed in the mixed cultures was found to be maximal at two temperatures, and a discussion is given of the causes thought to be operative in producing the double maximum.

The Synthesis and Migration of Nuclear Proteins during Mitosis and differentiation of Cells in Rats

1965 ◽  
Vol s3-106 (75) ◽  
pp. 229-240
Author(s):  
R. T. SIMS
Keyword(s):  
Granular Cell ◽  
Nuclear Proteins ◽  
Photographic Emulsion ◽  
Metaphase Chromosomes ◽  
Interphase Nuclei ◽  
Cell Layers ◽  
The Difference ◽  
Mitotic Figures ◽  
And Migration ◽  
Silver Grains

Hooded rats were given an intraperitoneal injection of 3H-tyrosine, and killed in pairs 10 min, 30 min, 12 h, 36 h, 7 days, and 30 days later. A piece of skin with white growing hair, and the tongue, were taken from each animal and radioautographs were prepared. Silver grains were counted over whole nuclei and whole mitotic figures of the germinal cells and whole nuclei of differentiating cells of both tissues. It was found that the interphase nuclei have significantly more silver grains over them than the chromosomes at all stages of mitosis and there are virtually no grains over metaphase, anaphase, and early telophase chromosomes in both tissues of all the animals killed up to 36 h after the injection. The difference between the grain counts over the interphase nuclei and the chromosomes of dividing cells is at least 20-fold at 30 min in the hair matrix, at least 5-fold at 30 min in the tongue and at 36 h in both tissues. It was established that the differences observed between the radioactivities of the nuclei and chromosomes of mitotic figures are real from estimates of: the radioactivity of the cell cytoplasm, volumes of the metaphase chromosomes and interphase nuclei within 1µ of the photographic emulsion, and the volumes of cytoplasm separating the photographic emulsion and these structures. No protein synthesis was demonstrable in the chromosomes during metaphase, anaphase, and early telophase. Nuclear proteins leave the chromosomes during prophase and prometaphase and return to the nucleus during late telophase. The cells in the matrix and upper bulb of the growing hair follicle and those in the germinal, prickle, and granular cell layers of the tongue are in different functional states; 30 min after injection of 3H-tyrosine they have different amounts of it in their nuclear proteins. It is suggested that the amount incorporated into each nucleus is related to the rate at which proteins are being synthesized by the cell.

scholarly journals Demography and feeding behavior of Stenostomum leucops (Dugés, 1828)

2016 ◽  
Vol 75 (s1) ◽  
Author(s):  
Alma R. Núñez-Ortiz ◽  
Sarma Nandini ◽  
S.S.S. Nandini
Keyword(s):  
Functional Response ◽  
Food Preference ◽  
Type Ii ◽  
Final Density ◽  
Two Temperatures ◽  
The Difference ◽  
Growth Experiments ◽  
Pelagic Communities ◽  
Type Ii Functional Response ◽  
Planktonic Communities

<p>Freshwater turbellarians, despite their mainly benthic habits, interact with pelagic communities of rotifers and cladocerans. However, very little is known about their demographic characteristics, food preference and functional response. To fill that gap we studied one of the most widely spread species, <em>Stenostomum leucops</em>.  We conducted population growth experiments using abundant food (several rotifer and cladocerans species). To evaluate possible impact of <em>S. leucops</em> on planktonic communities, we conducted prey preference experiments at two temperatures: 18 and 23°C. The number of rotifers and cladocerans consumed was calculated by the difference between the initial and final density. We found that diets supplemented with fresh algae achieved higher <em>S. leucops</em> densities than those with detritus supplements in their diets. In the case of animal diets, <em>Euchlanis dilatata</em> allowed <em>S. leucops</em> reach higher densities than the other zooplankton species; <em>E. dilatata</em> was positively selected for in the selectivity study at both 18 and 23°C.  <em>Stenostomum leucops</em> showed a type II functional response on rotifers and the cladoceran <em>Alona glabra</em>. Our results suggest that <em>S. leucops</em> select their prey according to their vulnerability using different mechanisms, which optimize their food intake.</p>

scholarly journals Four Types of LME Cracks in RSW of Zn-Coated AHSS

2020 ◽  
Vol 99 (3) ◽  
pp. 75s-92s ◽  
Author(s):  
SIVA PRASAD MURUGAN ◽  
◽  
YEONG-DO PARK ◽  
VIJEESH VIJAYAN ◽  
CHANGWOOK JI
Keyword(s):  
Tensile Stress ◽  
Synergetic Effect ◽  
High Strength Steels ◽  
High Strength ◽  
Liquid Zinc ◽  
Effect Of Temperature ◽  
Advanced High Strength Steels ◽  
Type D ◽  
The Difference

Zinc-coated advanced high-strength steels are known to be susceptible to liquid metal embrittlement (LME) cracking during resistance spot welding (RSW). Despite numerous reports with regard to LME during RSW, a systematic approach has not been proposed for the classification of cracks based on the cracking mechanism. The objective of this study was to characterize the LME cracks at various RSW locations, and thereby propose a classification method to identify the mechanism of the LME cracks at each location. The experimental results revealed the LME cracks were concentrated at certain weld locations and exhibited different features in terms of length, number, and orientation, owing to the synergetic effect of temperature, stress, microstructure, time of exposure to liquid zinc, and time of exposure to tensile stress at the corresponding lo-cations. Thus, the LME cracks were classified into four categories, namely type A, type B, type C, and type D, based on the formation location. The effect of time of exposure to liquid zinc and tensile stress on LME cracking revealed the time dependency of LME in RSW. The nature of contact be-tween the electrode and the sheet, and the heat input during welding, were found to be the main reasons for the difference in the thermal, mechanical, and metallurgical characteristics of various crack locations, which caused the formation of various LME crack types.

Effect of temperature differentials upon reconstitution of embryonic primordia in Ambystoma

Development ◽  
1971 ◽  
Vol 25 (3) ◽  
pp. 339-345
Author(s):  
Jean Piatt
Keyword(s):  
Statistical Analysis ◽  
Ambystoma Maculatum ◽  
Effect Of Temperature ◽  
Otic Vesicle ◽  
Regenerative Capacity ◽  
Rate Of Development ◽  
The Difference ◽  
The Right ◽  
Two Temperature

Eggs of Ambystoma maculatum in early stages of development were separated into two groups and maintained at 5 and 14 °C, respectively. In one series of animals comprising both temperature groups, the right otic vesicle was extirpated at stage 27. In another series the right forelimb disc was extirpated at stage 30. Following operation, animals of both groups were kept at 18 °C. Frequency and extent of reconstitution were compared between the two temperature groups. The 5° group was superior to the 14° group in the number of ears and forelimbs reconstituted. The extent of ear reconstitution and the initial quality of forelimb reconstitution were also superior in the 5° group. Statistical analysis of the data indicates that the difference between the two temperature groups is highly significant in both series. It is concluded that a slower pre-operative rate of development, caused by hypothermia, enhances the regenerative capacity of both ear and forelimb fields in the salamander embryo.

Hibernation, temperature and rates of oxidative phosphorylation by heart mitochondria

1960 ◽  
Vol 198 (2) ◽  
pp. 463-466 ◽  
Author(s):  
Frank E. South
Keyword(s):  
Oxygen Consumption ◽  
Oxidative Phosphorylation ◽  
Incubation Temperature ◽  
Regression Line ◽  
Vertical Displacement ◽  
Heart Mitochondria ◽  
Oxidative Enzymes ◽  
Effect Of Temperature ◽  
The Difference

The effect of temperature on rates of oxidative phosphorylation (pyruvate substrate) by heart mitochondria obtained from hibernating hamsters, control hamsters and rats was studied. Apparent energies of activation ( Ea) determined between 5° and 24°C were, respectively, 20.4, 20.8 and 28.3 Kcal. for the rates of oxygen consumption and 20.6, 21.4 and 29.5 Kcal. for the rates of phosphorylation. The difference between the rats and either group of hamsters were significant statistically. The slope of the regression line fitted to the data obtained from hibernating animals did not differ significantly from that of the control hamsters. However, a parallel vertical displacement of the lines indicated a probable increase in these oxidative enzymes upon preparation for, or during, hibernation. No significant alterations in the efficiency of oxidative phosphorylation with variations in the incubation temperature were noted in any of the preparations.

A study of organo-hectorite clay crystallization

Clay Minerals ◽  
1997 ◽  
Vol 32 (1) ◽  
pp. 29-40 ◽  
Author(s):  
K. A. Carrado ◽  
P. Thiyagarajan ◽  
K. Song
Keyword(s):  
Room Temperature ◽  
Structural Integrity ◽  
Effect Of Temperature ◽  
Clay Layer ◽  
Layer Formation ◽  
Surface Areas ◽  
Line Shape Analysis ◽  
Long Time ◽  
Organometallic Molecules

AbstractA method has been developed to synthesize organo-hectorite clays directly from a Mg-silicate gel containing organic or organometallic molecules that are expected to be incorporated within the interlayer space. Complete crystallization occurs upon aqueous reflux for 48 h. The progress of clay layer formation was monitored by X-ray powder diffraction (XRD), differential thermal gravimetry (DTG), and infrared (IR) spectroscopy. Evidence of clay XRD peaks occurs after just 4 h of hydrothermal treatment, and Mg(OH)2 is no longer observable after 14 h. Observable changes in DTG and IR occur at about this time as well. Warren line-shape analysis of the 110 reflection indicates that when growth is complete the clay lamellae are on average ∼50% and 25% of the size of natural hectorites and montmorillonites, respectively. The N2 BET surface areas for all materials are also compared. Small angle neutron scattering shows that addition of tetraethyl ammonium (TEA) ions does not alter the structural integrity over that of the purely inorganic form of Li-hectorite, but that use of a cationic polymer does significantly alter the microstructure. The effect of temperature is critical, for at room temperature only the layered Mg hydroxide mineral brucite crystallizes unless very long time scales are used. The crystallizations carried out at room temperature show that clay will form after about 3 months, but that the presence of organics (at least TEA) acts to hinder this process greatly. The role of the organic molecules on silicate clay layer formation is compared with the role of organics in zeolite synthesis.

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