日
関

WordNet

saclike structure in which ascospores are formed through sexual reproduction of ascomycetes
a sudden turning point in a persons life (similar to the sudden conversion of the Apostle Paul on the road from Jerusalem to Damascus of arrest Christians)
a hard resilient steel often decorated and used for sword blades (同)Damask steel

PrepTutorEJDIC

ダマスカス(Syriaの首部)

Wikipedia preview

出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2015/09/25 18:48:21」(JST)

wiki en

[Wiki en表示]

Asci of Morchella elata. Phase contrast image.

There are 8 ascospores in each ascus of Sordaria fimicola.

An ascus (plural asci; from Greek ἀσκός ảskós 'skin bag'^[1]) is the sexual spore-bearing cell produced in ascomycete fungi. Asci usually contain eight ascospores, produced by meiosis followed, in most species, by a mitotic cell division. However, asci in some genera or species can occur in numbers of one (e.g. Monosporascus cannonballus), two, four, or multiples of four. In a few cases, the ascospores can bud off conidia that may fill the asci (e.g. Tympanis) with hundreds of conidia, or the ascospores may fragment, e.g. some Cordyceps, also filling the asci with smaller cells. Ascospores are nonmotile, usually single celled, but not infrequently may be coenocytic (lacking a septum), and in some cases coenocytic in multiple planes. Mitotic divisions within the developing spores populate each resulting cell in septate ascospores with nuclei. The term ocular chamber, or oculus, refers to the epiplasm (the portion of cytoplasm not used in ascospore formation) that is surrounded by the "bourrelet" (the thickened tissue near the top of the ascus).^[2]

In many cases the asci are formed in a regular layer, the hymenium, in a fruiting body which is visible to the naked eye, here called an ascocarp or ascoma. In other cases, such as single-celled yeasts, no such structures are found. In rare cases asci of some genera can regularly develop inside older discharged asci one after another, e.g. Dipodascus.

Asci normally release their spores by bursting at the tip, but they may also digest themselves passively releasing the ascospores either in a liquid or as a dry powder. Typically, actively discharging asci have a specially differentiated tip, either a pore or an operculum. In some hymenium forming genera, when one ascus bursts, it can trigger the bursting of many other asci in the ascocarp resulting in a massive discharge visible as a cloud of spores – the phenomenon called "puffing". This is an example of positive feedback. A faint hissing sound can also be heard for species of Peziza and other cup fungi.

Asci, notably those of Neurospora crassa, have been used in laboratories for studying the process of meiosis, because the four cells produced by meiosis line up in regular order. By modifying genes coding for spore color and nutritional requirements, the biologist can study crossing over and other phenomena. The formation of asci and their use in genetic analysis are described in detail in Neurospora crassa.

Asci of most Pezizomycotina develop after the formation of croziers at their base. The croziers help maintain a brief dikaryon. The compatible nuclei of the dikaryon merge forming a diploid nucleus that then undergoes meiosis and ultimately internal ascospore formation. Members of the Taphrinomycotina and Saccharomycotina do not form croziers.

Ascus classification

Asci of Hypomyces chrysospermus (they are unitunicate-inoperculate). DIC image.

The form of the ascus, the capsule which contains the sexual spores, is important for classification of the Ascomycota. There are four basic types of ascus.

A unitunicate-operculate ascus has a "lid", the Operculum, which breaks open when the spores ripen and in this way sets them free. Unitunicate-operculate asci only occur in those ascocarps which have apothecia, for instance the morels. 'Unitunicate' means 'single-walled'.
Instead of an operculum, a unitunicate-inoperculate ascus has an elastic ring that functions like a pressure valve. On ripening it briefly expands and so lets the spores shoot out. This type appears both in apothecia and in perithecia; an example is the illustrated Hypomyces chrysospermus.

Ascus of Saccharomyces cerevisiae containing a tetrad of four spores

A bitunicate ascus is enclosed in a double wall. This consists of a thin, brittle outer shell and a thick elastic inner wall. When the spores are ripe, the shell splits open so that the inner wall can take up water. As a consequence this begins to extend with its spores until it protrudes above the rest of the ascocarp so that the spores can escape into free air without being obstructed by the bulk of the fruiting body. Bitunicate asci occur only in pseudothecia and are found only in the classes Dothideomycetes and Chaetothyriomycetes (which were formerly united in the old class Loculoascomycetes). Examples: Venturia inaequalis (apple scab) and Guignardia aesculi (Brown Leaf Mold of Horse Chestnut).
Prototunicate asci are mostly spherical in shape and they have no active dispersal mechanism at all. The ripe ascus wall simply dissolves so that the spores can escape, or it is broken open by other influences such as animals. Asci of this type can be found both in perithecia and in cleistothecia, for instance with Dutch elm disease (Ophiostoma). This is something of a catch-all term for cases which do not fit into the other three ascus types, and they probably belong to several independent groups which evolved separately from unitunicate asci.

References

^ [1]
^ Hawksworth DL. (2013). Ascomycete Systematics: Problems and Perspectives in the Nineties. Springer. p. 116. ISBN 978-1-4757-9290-4.

External links

IMA Mycological Glossary: Ascus
APSnet Illustrated Glossary of Plant Pathology: Ascus^{[dead link]}

UpToDate Contents

全文を閲覧するには購読必要です。 To read the full text you will need to subscribe.

1. 子宮頚部細胞診：異型扁平上皮細胞（ASC-USおよびASC-H）の評価 cervical cytology evaluation of atypical squamous cells asc us and asc h
2. 子宮頸部上皮内腫瘍：低悪性度および高悪性度病変のマネージメント cervical intraepithelial neoplasia management of low grade and high grade lesions
3. 子宮頚部および膣細胞診：結果の解釈 cervical and vaginal cytology interpretation of results
4. 子宮頸癌のスクリーニング screening for cervical cancer
5. 子宮頸癌スクリーニング検査：子宮頸部細胞診およびヒトパピローマウイルス検査の技術 cervical cancer screening tests techniques for cervical cytology and human papillomavirus testing

English Journal

Crosses Heterozygous for Hybrid Neurospora Translocation Strains Show Transmission Ratio Distortion Disfavoring Homokaryotic Ascospores Made Following Alternate Segregation.

Giri DA1, Rekha S2, Kasbekar DP3.
G3 (Bethesda, Md.).G3 (Bethesda).2016 Aug 9;6(8):2593-600. doi: 10.1534/g3.116.030627.
By introgressing Neurospora crassa translocations into N. tetrasperma, we constructed heterokaryons bearing haploid nuclei of opposite mating types, and either the translocation and normal sequence chromosomes (i.e., [T + N]) or a duplication and its complementary deficiency (i.e., [Dp + Df]). The [
PMID 27317785

Hybrid Capture 2 and cobas human papillomavirus assays perform similarly on SurePath samples from women with abnormalities.

Fornari D1,2, Rebolj M3, Bjerregård B2, Lidang M2, Christensen I2, Høgdall E2, Bonde J1,3.
Cytopathology : official journal of the British Society for Clinical Cytology.Cytopathology.2016 Aug;27(4):249-60. doi: 10.1111/cyt.12311. Epub 2016 Mar 17.
OBJECTIVE: In two laboratories (Departments of Pathology, Copenhagen University Hospitals of Herlev and Hvidovre), we compared cobas and Hybrid Capture 2 (HC2) human papillomavirus (HPV) assays using SurePath® samples from women with atypical squamous cells of undetermined significance (ASCUS) at �
PMID 26990233

Role of cervical cytology in surveillance after radical trachelectomy for cervical cancer.

Brown AJ1, Shah JS2, Fleming ND3, Nick AM4, Soliman PT3, Chisholm GB3, Schmeler KM3, Ramirez PT3, Frumovitz M3.
Gynecologic oncology.Gynecol Oncol.2016 Aug;142(2):283-5. doi: 10.1016/j.ygyno.2016.05.030. Epub 2016 Jun 6.
OBJECTIVE: There are currently no standard guidelines on the use of Papanicolaou (Pap) tests for surveillance after radical trachelectomy for cervical cancer. The goal of this study was to determine the usefulness of Pap tests in routine surveillance after radical trachelectomy for cervical cancer.M
PMID 27246304

Japanese Journal

Prevalence of High-Risk Human Papillomavirus (HR-HPV) Infection among Women with Normal and Abnormal Cervical Cytology in Myanmar

Mu-Mu-Shwe,Harano Teruo,Okada Shigeru,Aye-Aye-Win,Khin-Saw-Aye,Hlaing-Myat-Thu,Mo-Mo-Win,Khin-Khin-Oo,Myo-Khin
Acta Medica Okayama 68(2), 79-87, 2014-04
… Among them, 762 women (43.0%) had a normal smear, and 866(48.9%) and 87 (4.9%) were diagnosed with inflammatory smears and atypical squamous cells of undetermined significance (ASCUS), respectively. … HR-HPV were identified in 35.5% (22/62) of inflammatory smears, 60% (6/10) of ASCUS, 86.7% (13/15) of LSIL, 50% (3/6) of HSIL, 100% (3/3) of SCC and 5% (1/20) of normal cytology. …
NAID 120005425626

当院検査部におけるベセスダシステム ASC-US 亜分類の試みとその有用性についての検討

小保方亜光,斉藤誠人,永瀬泰平,櫻井信司
日本臨床細胞学会雑誌 53(6), 441-445, 2014
… 例は存在する.方法 : 今回, ASC-US のカテゴリーを, 異形成を強く疑う ASCUS favor dysplasia (ASCUS-D) と, 積極的には疑わない ASCUS not otherwise specified (ASCUS-NOS) に亜分類し, ハイリスク HPV の陽性率, 生検の結果について比較検討した.成績 : 頸部細胞診 14655 例中, ASCUS-NOS 354 例, ASCUS-D 150 例で, HPV 陽性率はおのおの 19.1%, 54.1%であった. …
NAID 130004885821

子宮頸癌細胞診におけるスコアリングシステムを用いたASC-US の評価:—NILM, ASCUS-NOS と ASCUS-D 鑑別のポイント—

斉藤誠人,小保方亜光,永瀬泰平,櫻井信司
日本臨床細胞学会雑誌 53(6), 435-440, 2014
… 目的 : われわれは, ハイリスク HPV 感染の頻度が低い ASCUS not otherwise specified (ASCUS-NOS) と, 頻度の高い ASCUS favor dysplasia (ASCUS-D) を感覚的に区別してきた. …
NAID 130004885820

Related Pictures

ASCUS : Atypical Cells of Undetermined Significance. ASCUS at Northeastern Ohio Universities College of Medicine - StudyBlue 301 Moved Permanently Ascus | Wiki | Everipedia Exercise 7 - Biology 112 with Aufderheide at Texas A&M University - StudyBlue Atypical squamous epithelial cells of uncertain signficance (ASCUS) | Eurocytology