Responses of metamorphosing Taricha torosa to x rays

1974 ◽  
Vol 52 (6) ◽  
pp. 671-676
Author(s):  
H. M. McCurdy ◽  
F. T. Algard ◽  
G. B. Friedmann
Keyword(s):  
Single Dose ◽  
Sample Population ◽  
X Rays ◽  
Larval Form ◽  
Triggering Mechanism ◽  
Pigment Pattern ◽  
Taricha Torosa ◽  
Complete Metamorphosis

A single dose of 1000 rads of x rays administered to metamorphosing Taricha torosa larvae interferes selectively with some elements of the metamorphosing process without, apparently, affecting any major triggering mechanism. Though the predominant result is a failure to complete metamorphosis, metamorphosed irradiates showing larval pigmentation, vestigial gills, and non-protuberant eyes have been observed. Arrest of the normal thickening of the epidermis during metamorphosis and of the associated development of the epidermal melanophores is followed by regression of the pigment pattern to the larval form. This 1000-rad dose appears to kill half of a sample population in 30 days. A single dose of 200 rads, while allowing completion of metamorphosis, is fatal within some 3 months. The metamorphosed animals show predominantly adult characteristics.

Response of newt larvae to X-irradiation

1970 ◽  
Vol 48 (5) ◽  
pp. 1017-1021
Author(s):  
G. B. Friedmann ◽  
H. M. McCurdy ◽  
F. T. Algard
Keyword(s):  
Life Span ◽  
Dose Response ◽  
Progenitor Cell ◽  
X Rays ◽  
Cell Type ◽  
Taricha Torosa ◽  
Age Dependent ◽  
X Irradiation ◽  
Complete Metamorphosis

Graded doses of from 200 to 2000 rad of x-rays were administered to premetamorphic Taricha torosa larvae of various ages. General stunting, specific malformation, pigmentary damage, and a very shortened life-span occurred at all doses. There is an age-dependent dose response; some animals exposed to 200 and 600 rad survived to complete metamorphosis. Evidence is presented supporting a view that postmetamorphic epidermal melanocytes may be derived largely by division of an unpigmented progenitor cell type.

Time-related changes in lymphatic clearance in pig skin after a single dose of 18 Gy of X rays

1991 ◽  
Vol 64 (768) ◽  
pp. 1140-1146 ◽  
Author(s):  
P. S. Mortimer ◽  
R. H. Simmonds ◽  
M. Rezvani ◽  
M. E. C. Robbins ◽  
T. J. Ryan ◽  
...  
Keyword(s):  
Single Dose ◽  
X Rays ◽  
Pig Skin

Preoperative Use of a Single Dose of X-Rays

1964 ◽  
Vol 89 (2) ◽  
pp. 398 ◽  
Author(s):  
W. RODGER INCH
Keyword(s):  
Single Dose ◽  
X Rays

scholarly journals Complete metamorphosis of insects

2019 ◽  
Vol 374 (1783) ◽  
pp. 20190063 ◽  
Author(s):  
Jens Rolff ◽  
Paul R. Johnston ◽  
Stuart Reynolds
Keyword(s):  
Adult Stage ◽  
Pupal Stage ◽  
Life Stages ◽  
Micro Ct ◽  
Larval Form ◽  
Theme Issue ◽  
The Cost ◽  
Ephemeral Resources ◽  
Complete Metamorphosis

The majority of described hexapod species are holometabolous insects, undergoing an extreme form of metamorphosis with an intercalated pupal stage between the larva and adult, in which organs and tissues are extensively remodelled and in some cases completely rebuilt. Here, we review how and why this developmental strategy has evolved. While there are many theories explaining the evolution of metamorphosis, many of which fit under the hypothesis of decoupling of life stages, there are few clear adaptive hypotheses on why complete metamorphosis evolved. We propose that the main adaptive benefit of complete metamorphosis is decoupling between growth and differentiation. This facilitates the exploitation of ephemeral resources and enhances the probability of the metamorphic transition escaping developmental size thresholds. The evolution of complete metamorphosis comes at the cost of exposure to predators, parasites and pathogens during pupal life and requires specific adaptations of the immune system at this time. Moreover, metamorphosis poses a challenge for the maintenance of symbionts and the gut microbiota, although it may also offer the benefit of allowing an extensive change in microbiota between the larval and adult stages. The regulation of metamorphosis by two main players, ecdysone and juvenile hormone, and the related signalling cascades are now relatively well understood. The mechanics of metamorphosis have recently been studied in detail because of the advent of micro-CT and research into the role of cell death in remodelling tissues and organs. We support the argument that the adult stage must necessarily have preceded the larval form of the insect. We do not resolve the still contentious question of whether the larva of insects in general originated through the modification of existing preadult forms or through heterochrony as a modified embryonic stage (pronymph), nor whether the holometabolous pupa arose as a modified hemimetabolous final stage larva. This article is part of the theme issue ‘The evolution of complete metamorphosis’.

scholarly journals ROENTGEN RAY INTOXICATION

1923 ◽  
Vol 38 (6) ◽  
pp. 725-730 ◽  
Author(s):  
S. L. Warren ◽  
G. H. Whipple
Keyword(s):  
Small Intestine ◽  
Single Dose ◽  
Cell Injury ◽  
Cumulative Effect ◽  
X Rays ◽  
Epithelial Injury ◽  
X Ray ◽  
Tumor Tissues ◽  
Small Doses ◽  
Repeated Doses

A single large dose of x-rays over the abdomen will cause a definite injury of the mucosa of the small intestine and the severity of the clinical intoxication seems to parallel this recognizable epithelial injury. This clinical intoxication lasts 4 to 6 days if the x-ray dose is sublethal. Subsequent doses of radiation given within this period of clinical intoxication give recognizable evidence of summation or a cumulative effect. Small but repeated doses of radiation given within a 5 or 6 day period will cause practically the same cell injury and clinical intoxication as will a single dose representing the sum of the small doses expressed in milliampere minutes. Doses of radiation given at 6 day or longer intervals show no evidence of summation. The reaction of this relatively sensitive intestinal epithelium to radiation may be similar to the reaction of certain deep lying tumor tissues to x-ray therapy and our experiments may give information of value to physicians concerned with x-ray or radium therapy.

scholarly journals COVID-19 Tragic Pandemic: Concerns over Unintentional “Directed Accelerated Evolution” of Novel Coronavirus (SARS-CoV-2) and Introducing a Modified Treatment Method for ARDS

2020 ◽  
Vol 10 (2) ◽  
Author(s):  
Ghadimi-Moghadam A
Keyword(s):  
Single Dose ◽  
Background Radiation ◽  
Treatment Method ◽  
Antiviral Drugs ◽  
Current Status ◽  
X Rays ◽  
The Novel ◽  
High Background ◽  
Accelerated Evolution ◽  
Novel Coronavirus

Abstract Global health authorities are trying to work out the current status of the novel coronavirus (COVID-19) outbreak and explore methods to reduce the rate of its transmission to healthy individuals. In this viewpoint we provide insights concerning how health care professionals can unintentionally shift the novel coronavirus type to more drug-resistant forms. It is worth noting that viruses usually have different sensitivities to physical and chemical damaging agents such antiviral drugs, UV and heat ranging from extremely sensitive (ES) to extremely resistant (ER) based on a bell-shaped curve. Given this consideration, the widespread infection of people with such ER viruses would be a real disaster. Here, we introduce a modified treatment method for COVID-19-associated pneumonia. In this proposed method, COVID-19 patients will receive a single dose of 100, 180 or 250 mSv X-ray radiation that is less than the maximum annual radiation dose of the residents of high background radiation areas of Ramsar that is up to 260 mSv. In contrast with antiviral drugs, a single dose of either 100, 180 or 250 mSv of low LET X-rays cannot exert a significant selective pressure on the novel coronavirus (SARS-CoV-2) and hence does not lead to directed accelerated evolution of these viruses. Moreover, Low Dose Radiation (LDR) has the capacity of modulating excessive inflammatory responses, regulating lymphocyte counts, and controling bacterial co-infections in patients with COVID-19.

scholarly journals STUDIES ON X-RAY EFFECTS

1926 ◽  
Vol 43 (1) ◽  
pp. 61-70 ◽  
Author(s):  
Robert T. Hance ◽  
Harry Clark
Keyword(s):  
Single Dose ◽  
Complete Recovery ◽  
Maximum Effect ◽  
X Rays ◽  
Division Rate ◽  
Appreciable Difference ◽  
X Ray ◽  
Initial Depression ◽  
Ray Effects ◽  
Number Of Individuals

Two races of paramecium were submitted for varying lengths of time to x-radiation and a large number of individuals were observed to determine the effect on the rate of division. The division rate of both races suffered a slight initial depression lasting for 2 to 5 days following the exposure. This depression is followed by complete recovery. Within rather wide limits the length of the exposure has, in these experiments, made no appreciable difference. Apparently the maximum effect of the x-rays is produced by relatively short exposures. Continued radiation produces little further change until exposures of 3 and 4 hours are used, when precisely the opposite results are obtained from those obtained with shorter exposures. Doses repeated at various intervals have in general failed to interfere more markedly with the division rate than a single dose. Repeated radiation causes the cells to become slightly swollen without apparent interference with their viability.

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