The Fine Structure of Primordial Germ Cells of the Rat

1973 ◽  
Vol 31 ◽  
pp. 634-635
Author(s):  
E. M. Eddy
Keyword(s):  
Endoplasmic Reticulum ◽  
Life History ◽  
Fine Structure ◽  
Rough Endoplasmic Reticulum ◽  
Germ Cells ◽  
Fibrous Material ◽  
Primordial Germ Cells ◽  
The Other ◽  
Large Size ◽  
History Of

Primordial germ cells are readily recognizable in embryos of the rat due to their large size, generally rounded shape and prominent nuclei with uniformly dispersed heterochromatin. They often have blunted pseudopodal processes at one end and small ruffles or trailing processes at the other, characteristics expected from their known ameboid activity- and migratory abilities. Also, the cytoplasm is rich in polyribosomes and contains a modest amount of rough endoplasmic reticulum and the mitochondria are frequently larger and less dense than those of adjacent somatic cells.In addition to these general characteristics, there are features unique to germ cells which allow them to be identified with certainty. These are: 1) small vesicles containing an irregular, dense core and 2) discrete accumulations of fibrous material known as nuage. Both of these features are present in other species and at other times in the life history of germ cells. The dense-cored vesicles have been noted in fetal and early postnatal mouse oogonia and oocytes, and in hamster and rabbit oocytes.

Fine structure of compound eyes of cicindela tranquebarica herbst (coleoptera: cicindelidae)

1978 ◽  
Vol 36 (2) ◽  
pp. 604-605
Author(s):  
Janice E. Kuster
Keyword(s):  
Endoplasmic Reticulum ◽  
Fine Structure ◽  
Rough Endoplasmic Reticulum ◽  
Cell Nucleus ◽  
The Other ◽  
Pigment Cells ◽  
Compound Eyes ◽  
Basal Bodies ◽  
Protein Deposits ◽  
Corneal Lens

The fine structure of photopic eucone eyes of Cicindela tranquebarica adults was examined using cryofracture SEM, TEM, and freeze-etch techniques. A “subcorneal layer” can be distinguished between the corneal lens and crystalline cone. In surface view (Fig. 1) this layer consists of concave polygons (po). It has parabolic lamellae (lm) of endocuticle consisting of microfibrils (mf) having a chitin core with protein deposits along their lengths (Fig. 2). Two primary pigment cells (lp) are devoid of pigment granules, but are rich in rough endoplasmic reticulum (rer) and surround a crystalline thread (ct) (Fig. 3). Extensions of the crystalline thread form inter-retinular fibers (f) containing microtubules between retinula cells 1/2, 3/4, 5/6, and 7/1 (Figs. 4, 5).Distal to each retinula cell nucleus are two basal bodies (bb), one perpendicular to the other (Fig. 4). The proximal body extends two fibrillar feet which fuse to form a horizontally banded ciliary rootlet which extends the retinula length peripheral to the rhabdom.

Memoirs: A Study of the Life-history of Bucephalus Haimeanus; a Parasite of the Oyster

1906 ◽  
Vol s2-49 (196) ◽  
pp. 635-690
Author(s):  
DAVID HILT TENNENT
Keyword(s):  
Life History ◽  
Experimental Evidence ◽  
Germ Cells ◽  
The Other ◽  
Small Cells ◽  
Adverse Conditions ◽  
Polar Bodies ◽  
History Of ◽  
Von Siebold ◽  
Near Future

The observations detailed in this paper maybe summarised as follows: 1. Germ-cells which arise within the wall of the sporocyst of G. gracilescens give off small cells, which may be considered of the nature of polar bodies, segment, and develop to the cercaria B. haimeanus. 2. The cercaria B. haimeanus, Lacaze-Duthiers (1854) = B. cuculus, McCrady (1868), parasitic in the oyster, differs structurally from B. poly tnorphus, von Baer, parasitic in fresh water mussels, only in the shape of the tails. 3. G. gracilescens, Wagener (1852) parasitic in Lophius piscatorius = Gasterostomum sp., Linton, 1899, parasitic in Tylosurus mar in us, differs from G. fimbriatum, von Siebold, only in habitat (one is a marine, the other a, freshwater, form), and slightly dissimilar larva. 4. B. haimeanus, as shown by experimental evidence, is a larval stage of G. gracilescens. 5. Experimental evidence shows that supposedly different species are physiological varieties of the same species. 6. The presence of the sporocysts and cercaria of G. gracilescens in the oyster prevents the formation of reproductive elements, and also renders the host incapable of withstanding adverse conditions. 7. B. haimeanus thrives best in oysters growing in brackish water. Its growth is inhibited by increased salinity. It will be noticed that there is one gap in my account of the life-history of Gasterostomum. I have not yet proved the infection of oysters by embryos developed from the eggs of the adult. I hope to make this the object of experimental work within the near future.

scholarly journals On Apogamy and the development of Sporangia upon fern prothalli

1898 ◽  
Vol 63 (389-400) ◽  
pp. 56-61
Keyword(s):  
Life History ◽  
Point Of View ◽  
The Other ◽  
Normal Life ◽  
Other Hand ◽  
General Importance ◽  
Two Generations ◽  
History Of ◽  
Alternation Of Generations

The two most important deviations from the normal life-history of ferns, apogamy and apospory, are of interest in themselves, but acquire a more general importance from the possibility that their study may throw light on the nature of alternation of generations in archegoniate plants. They have been considered from this point of view Pringsheim, and by those who, following him, regard the two generations as homologous with one another in the sense that the sporophyte arose by the gradual modification of individuals originally resemblin the sexual plant. Celakovsky and Bower, on the other hand, maintaint the view tha t the sporophyte, as an interpolated stage in the life-history arising by elaboration of the zygote, a few thallophytes.

scholarly journals Effect of NaCl on seed germination in some Centaurium Hill. Species (Gentianaceae)

2007 ◽  
Vol 59 (3) ◽  
pp. 227-231 ◽  
Author(s):  
S. Zivkovic ◽  
M. Devic ◽  
B. Filipovic ◽  
Z. Giba ◽  
D. Grubisic
Keyword(s):  
Life History ◽  
Salt Tolerance ◽  
Seed Germination ◽  
Gibberellic Acid ◽  
White Light ◽  
The Other ◽  
Distilled Water ◽  
Nacl Concentration ◽  
History Of ◽  
Species Specific

The influence of high NaCl concentrations on seed germination in both light and darkness was examined in the species Centaurium pulchellum, C. erythraea, C. littorale, C. spicatum, and C. tenuiflorum. Salt tolerance was found to depend on the life history of the seeds. To be specific, seeds of all five species failed to complete germination when exposed to continuous white light if kept all the time in the presence of 100-200 mM and greater NaCl concentrations. However, when after two weeks NaCl was rinsed from the seeds and the seeds were left in distilled water under white light for an additional two weeks, all species completed germination to a certain extent. The percent of germination not only depended on NaCl concentration in the prior medium, but was also species specific. Thus, seeds of C. pulchellum, C. erythraea, and C. littorale completed germination well almost irrespective of the salt concentration previously experienced. On the other hand, seeds of C. tenuiflorum completed germination poorly if NaCl concentrations in the prior media were greater than 200 mM. When seeds after washing were transferred to darkness for an additional 14 days, they failed to complete germination if previously imbibed on media containing NaCl concentrations greater than 400 mM. However, the seeds of all species, even if previously imbibed at 800 mM NaCl, could be induced to complete germination in darkness by 1 mM gibberellic acid. .

Life on the edge: the ecology and life history of the tropidurine iguanid lizard Uranoscodon superciliosum

1990 ◽  
Vol 68 (7) ◽  
pp. 1366-1373 ◽  
Author(s):  
Jeffrey M. Howland ◽  
Laurie J. Vitt ◽  
Pamela T. Lopez
Keyword(s):  
Life History ◽  
Social Interaction ◽  
Sexual Dimorphism ◽  
Small Diameter ◽  
Habitat Specialization ◽  
Large Size ◽  
Tropical Wet Forest ◽  
History Of ◽  
Forest Streams ◽  
Small Forest

An Amazonian population of the iguanid lizard Uranoscodon superciliosum was studied in lowland tropical wet forest in central Pará, Brazil. These nonheliothermic lizards are restricted to densely vegetated habitats near (often over) water, particularly riverbanks and small forest streams, where they utilize small-diameter perches and feed on a wide variety of invertebrates, apparently at the water's edge. They mature at moderate to large size at an age of about 1.5 years. Production of moderate-sized clutches of eggs is seasonal, and reproduction and fat storage both cycle in association with rainfall and flooding. Although they occur in fairly high densities, social interaction is uncommon and sexual dimorphism is not pronounced. The ecology and life history of this lizard seem to be strongly influenced by the unusual habitat specialization.

Sex differentiation of germ cells in the teleost, Oryzias latipes, during normal embryonic development

Development ◽  
1972 ◽  
Vol 28 (2) ◽  
pp. 385-395
Author(s):  
Noriyuki Satoh ◽  
Nobuo Egami
Keyword(s):  
Germ Cells ◽  
Meiotic Prophase ◽  
Sex Differentiation ◽  
Primordial Germ Cells ◽  
Oryzias Latipes ◽  
The Other ◽  
Histological Structure ◽  
The Mean ◽  
Further Development ◽  
Normal Embryonic Development

Mitotic and meiotic activities of germ cells during early development in the medaka, Oryzias latipes, are dealt with in this report. Primordial germ cells were obviously distinguishable from somatic cells 3 days after fertilization and began to proliferate about 7 days after fertilization. The mean number of primordial germ cells increased during a period of 7–10 days after fertilization, reaching about 90 immediately before hatching. Newly hatched fry could be classified into two types according to the number and the nucleic activity of germ cells in the gonadal rudiment. One type consisted of fry containing about 100 germ cells and no cells in the meiotic prophase. In the other type of fry the number of germ cells increased by mitotic divisions and some of the cells began to enter into the meiotic prophase. During the course of further development the fry of the former type differentiated into males and the latter into females. Therefore it can be concluded that the morphological sex differentiation of germ cells occurs at the time of hatching. However, no sexual differences in the histological structure of somatic elements in the gonad are observable at that time.

The Odd Man Out in a Pioneer Cemetery at Seccombe Lake Park, San Bernardino, California

2020 ◽  
pp. 90-113
Author(s):  
Patricia M. Lambert
Keyword(s):  
Life History ◽  
Native American ◽  
Morphological Traits ◽  
The Other ◽  
European Ancestry ◽  
Latter Day Saints ◽  
Community Members ◽  
San Bernardino ◽  
History Of ◽  
The 19Th Century

In 1989, a pioneer cemetery associated with the 19th-century Latter-Day Saints colony in San Bernardino, California, was discovered during the construction of a baseball field. Among the remains of 12 individuals recovered from the cemetery were those of a young man of about 22 years, whose burial treatment differed notably from the other intact interments at the site. Unlike these coffin burials, Burial 5 was found in a sprawling position, apparently tossed unceremoniously into the grave pit. Dental morphological traits identified the genetic affinities of this man as Native American, perhaps a member of the local Cahuilla or Serrano tribes, whereas the other individuals appeared to be of European ancestry, an interpretation consistent with records kept by community members. A possible identity for this individual came from a journal account describing the shooting of an “Indian” by the local sheriff, who was then brought to the fort, died, and was buried before his fellow tribesmen arrived to determine what had transpired and perhaps to claim his remains. This chapter explores the identity and life history of this young man in the context of the history of the valley and the pioneer community in which he met his death.

The Biology of the Genus Pissodes. (George Heriot Research Fellowship Thesis.)

1902 ◽  
Vol 23 ◽  
pp. 319-358
Author(s):  
R. Stewart MacDougall
Keyword(s):  
Life History ◽  
Economic Importance ◽  
The Other ◽  
Remedial Measures ◽  
Research Fellowship ◽  
History Of ◽  
The One ◽  
Harmful Insect

In the case of any harmful insect of economic importance, in order to war against it, or apply remedial measures at all intelligently, a knowledge of the life-history of the pest is necessary. This proposition will, I think, meet with such ready acceptance as to render proof unnecessary, but I might in illustration mention two cases which came under my own observation, where in the one case a knowledge of the round of life of the attacking insect saved a whole forest, and in the other proved of great importance.

Biography and (Global) Microhistory

2017 ◽  
Vol 11 (3) ◽  
Author(s):  
Mark Gamsa
Keyword(s):  
Life History ◽  
Northeast China ◽  
The Other ◽  
Historical Writing ◽  
Forthcoming Book ◽  
Recent Developments ◽  
History Of ◽  
German Origin ◽  
The One ◽  
The City

AbstractThis article has two goals. It reflects on the recent developments and agenda of an approach to historical writing that is now becoming known by the name global microhistory, and it analyses the attention which this approach pays to individual lives. It also explores some of the challenges in writing the biography of a city alongside the life history of a person. The city is Harbin, a former Russian-managed railway hub in Manchuria, today a province capital in Northeast China. The person is Baron Roger Budberg (1867–1926), a physician of Baltic German origin who arrived in Harbin during the Russo-Japanese war and remained there until his death, leaving published works and unpublished correspondence in German and Russian. My forthcoming book about Budberg and Harbin challenges the distinction between writing “biography”, on the one hand, and “history”, on the other, while navigating between the “micro” and “macro” layers of historical enquiry.

Epiphyllous Microorganisms as Palaeoclimate Estimators: The Developmental Sequence of Fungal 'Germlings' on their Living Host

1993 ◽  
Vol 6 (5) ◽  
pp. 377 ◽  
Author(s):  
AK Wells ◽  
RS Hill
Keyword(s):  
Life History ◽  
Host Species ◽  
The Other ◽  
Developmental Sequence ◽  
History Of

It is known that epiphyllous microorganisms have the potential to provide important information about palaeoclimates and palaeohabitats. Previous studies have shown one of the major candidates, fungal 'germlings', to be possibly climatically sensitive. In this study we demonstrate that at least two organisms are present as germlings, one an epiphyte and the other a saprophyte. While there is some evidence to support the hypothesis that grades of germlings represent a sequence of developmental steps, most data either refute this hypothesis or neither refute nor support it. We show that grade 1 and 2 germlings are unlikely to be reliable for predictive purposes, since their presence is not consistent among host species, and they may represent saprophytes as well as epiphytes. The ecology and life history of germlings is complex, and more data are required on these factors before they can be used for predictive purposes.

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