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Gerhold AR, Labbé JC, Singh R. Uncoupling cell division and cytokinesis during germline development in metazoans. Front Cell Dev Biol 2022; 10:1001689. [PMID: 36407108 PMCID: PMC9669650 DOI: 10.3389/fcell.2022.1001689] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2022] [Accepted: 10/17/2022] [Indexed: 11/06/2022] Open
Abstract
The canonical eukaryotic cell cycle ends with cytokinesis, which physically divides the mother cell in two and allows the cycle to resume in the newly individualized daughter cells. However, during germline development in nearly all metazoans, dividing germ cells undergo incomplete cytokinesis and germ cells stay connected by intercellular bridges which allow the exchange of cytoplasm and organelles between cells. The near ubiquity of incomplete cytokinesis in animal germ lines suggests that this is an ancient feature that is fundamental for the development and function of this tissue. While cytokinesis has been studied for several decades, the mechanisms that enable regulated incomplete cytokinesis in germ cells are only beginning to emerge. Here we review the current knowledge on the regulation of germ cell intercellular bridge formation, focusing on findings made using mouse, Drosophila melanogaster and Caenorhabditis elegans as experimental systems.
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Affiliation(s)
- Abigail R. Gerhold
- Department of Biology, McGill University, Montréal, QC, Canada
- *Correspondence: Abigail R. Gerhold, ; Jean-Claude Labbé,
| | - Jean-Claude Labbé
- Institute for Research in Immunology and Cancer (IRIC), Montréal, QC, Canada
- Department of Pathology and Cell Biology, Université de Montréal, Succ. Centre-ville, Montréal, QC, Canada
- *Correspondence: Abigail R. Gerhold, ; Jean-Claude Labbé,
| | - Ramya Singh
- Department of Biology, McGill University, Montréal, QC, Canada
- Institute for Research in Immunology and Cancer (IRIC), Montréal, QC, Canada
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2
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Wang ZH, Chen L, Li W, Chen L, Wang YP. Mitochondria transfer and transplantation in human health and diseases. Mitochondrion 2022; 65:80-87. [PMID: 35623561 DOI: 10.1016/j.mito.2022.05.002] [Citation(s) in RCA: 25] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Revised: 04/16/2022] [Accepted: 05/22/2022] [Indexed: 10/18/2022]
Abstract
Mitochondria are dynamic organelles responsible for energy production and cell metabolism. Disorders in mitochondrial function impair tissue integrity and have been implicated in multiple human diseases. Rather than constrained in host cells, mitochondria were recently found to actively travel between cells through nanotubes or extracellular vesicles. Mitochondria transportation represents a key mechanism of intercellular communication implicated in metabolic homeostasis, immune response, and stress signaling. Here we reviewed recent progress in mitochondria transfer under physiological and pathological conditions. Specifically, tumor cells imported mitochondria from adjacent cells in the microenvironment which potentially modulated cancer progression. Intercellular mitochondria trafficking also inspired therapeutic intervention of human diseases with mitochondria transplantation. Artificial mitochondria, generated through mitochondria genome engineering or mitochondria-nucleus hybridization, further advanced our understanding of mitochondrial biology and its therapeutic potential. Innovative tools and animal models of mitochondria transplantation will assist the development of new therapies for mitochondrial dysfunction-related diseases.
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Affiliation(s)
- Zi-Hao Wang
- Fudan University Shanghai Cancer Center, Key Laboratory of Breast Cancer in Shanghai, Shanghai Key Laboratory of Radiation Oncology, Cancer Institute, and The Shanghai Key Laboratory of Medical Epigenetics, Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 20032, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, China; The International Co-laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology, Shanghai 20032, China
| | - Lu Chen
- State Key Laboratory of Component-based Chinese Medicine, Tianjin University of Traditional Chinese Medicine, Tianjin 301617, China
| | - Wei Li
- School of Medical Imaging, Shanghai University of Medicine and Health Sciences, Shanghai 201318, China.
| | - Lingchao Chen
- Department of Neurosurgery, Huashan Hospital, Shanghai Medical College, Fudan University, National Center for Neurological Disorders, Shanghai Key Laboratory of Brain Function and Restoration and Neural Regeneration, Neurosurgical Institute of Fudan University, Shanghai Clinical Medical Center of Neurosurgery, Shanghai 200040, China.
| | - Yi-Ping Wang
- Fudan University Shanghai Cancer Center, Key Laboratory of Breast Cancer in Shanghai, Shanghai Key Laboratory of Radiation Oncology, Cancer Institute, and The Shanghai Key Laboratory of Medical Epigenetics, Institutes of Biomedical Sciences, Shanghai Medical College, Fudan University, Shanghai 20032, China; Department of Oncology, Shanghai Medical College, Fudan University, Shanghai 20032, China; The International Co-laboratory of Medical Epigenetics and Metabolism, Ministry of Science and Technology, Shanghai 20032, China.
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3
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Ikami K, Nuzhat N, Abbott H, Pandoy R, Haky L, Spradling AC, Tanner H, Lei L. Altered germline cyst formation and oogenesis in Tex14 mutant mice. Biol Open 2021; 10:269245. [PMID: 34156079 PMCID: PMC8249907 DOI: 10.1242/bio.058807] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2021] [Accepted: 05/12/2021] [Indexed: 11/24/2022] Open
Abstract
During oocyte differentiation in mouse fetal ovaries, sister germ cells are connected by intercellular bridges, forming germline cysts. Within the cyst, primary oocytes form via gaining cytoplasm and organelles from sister germ cells through germ cell connectivity. To uncover the role of intercellular bridges in oocyte differentiation, we analyzed mutant female mice lacking testis-expressed 14 (TEX14), a protein involved in intercellular bridge formation and stabilization. In Tex14 homozygous mutant fetal ovaries, germ cells divide to form a reduced number of cysts in which germ cells remained connected via syncytia or fragmented cell membranes, rather than normal intercellular bridges. Compared with wild-type cysts, homozygous mutant cysts fragmented at a higher frequency and produced a greatly reduced number of primary oocytes with precocious cytoplasmic enrichment and enlarged volume. By contrast, Tex14 heterozygous mutant germline cysts were less fragmented and generate primary oocytes at a reduced size. Moreover, enlarged primary oocytes in homozygous mutants were used more efficiently to sustain folliculogenesis than undersized heterozygous mutant primary oocytes. Our observations directly link the nature of fetal germline cysts to oocyte differentiation and development. Summary: Altered germline cyst formation and fragmentation due to defective germ cell connectivity leads to changes in oocyte differentiation and development in Tex14 mutant mice.
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Affiliation(s)
- Kanako Ikami
- Buck Institute for Research on Aging, 94949, Novato, CA, USA
| | - Nafisa Nuzhat
- Department of Cell and Developmental Biology, University of Michigan Medical School, 48109, Ann Arbor, MI, USA
| | - Haley Abbott
- Department of Cell and Developmental Biology, University of Michigan Medical School, 48109, Ann Arbor, MI, USA
| | - Ronald Pandoy
- Buck Institute for Research on Aging, 94949, Novato, CA, USA
| | - Lauren Haky
- Buck Institute for Research on Aging, 94949, Novato, CA, USA
| | - Allan C Spradling
- Department of Embryology, Carnegie Institution for Science, 21218, Baltimore, MD, USA
| | - Heather Tanner
- Buck Institute for Research on Aging, 94949, Novato, CA, USA
| | - Lei Lei
- Buck Institute for Research on Aging, 94949, Novato, CA, USA
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4
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Communal living: the role of polyploidy and syncytia in tissue biology. Chromosome Res 2021; 29:245-260. [PMID: 34075512 PMCID: PMC8169410 DOI: 10.1007/s10577-021-09664-3] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 05/10/2021] [Accepted: 05/16/2021] [Indexed: 01/22/2023]
Abstract
Multicellular organisms are composed of tissues with diverse cell sizes. Whether a tissue primarily consists of numerous, small cells as opposed to fewer, large cells can impact tissue development and function. The addition of nuclear genome copies within a common cytoplasm is a recurring strategy to manipulate cellular size within a tissue. Cells with more than two genomes can exist transiently, such as in developing germlines or embryos, or can be part of mature somatic tissues. Such nuclear collectives span multiple levels of organization, from mononuclear or binuclear polyploid cells to highly multinucleate structures known as syncytia. Here, we review the diversity of polyploid and syncytial tissues found throughout nature. We summarize current literature concerning tissue construction through syncytia and/or polyploidy and speculate why one or both strategies are advantageous.
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5
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Lu K, Jensen L, Lei L, Yamashita YM. Stay Connected: A Germ Cell Strategy. Trends Genet 2017; 33:971-978. [PMID: 28947158 DOI: 10.1016/j.tig.2017.09.001] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2017] [Revised: 08/24/2017] [Accepted: 09/05/2017] [Indexed: 01/20/2023]
Abstract
Germ cells develop as a cyst of interconnected sibling cells in a broad range of organisms in both sexes. A well-established function of intercellular connectivity is to transport cytoplasmic materials from 'nurse' cells to oocytes, a critical process for developing functional oocytes in ovaries of many species. However, there are situations where connectivity exists without a nursing mechanism, and the biological meaning of such connectivity remains obscure. In this review, we summarize current knowledge on the formation of intercellular connectivity, and discuss its meaning by visiting multiple examples of germ cell connectivity observed in evolutionarily distant species.
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Affiliation(s)
- Kevin Lu
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA; Medical Scientist Training Program, University of Michigan, Ann Arbor, MI 48109, USA; Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA
| | - Lindy Jensen
- Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; Department of Molecular and Integrative Physiology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Lei Lei
- Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA
| | - Yukiko M Yamashita
- Cellular and Molecular Biology Program, University of Michigan, Ann Arbor, MI 48109, USA; Life Sciences Institute, University of Michigan, Ann Arbor, MI 48109, USA; Department of Cell and Developmental Biology, University of Michigan, Ann Arbor, MI 48109, USA; Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI 48109, USA.
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6
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Haglund K, Nezis IP, Stenmark H. Structure and functions of stable intercellular bridges formed by incomplete cytokinesis during development. Commun Integr Biol 2014. [DOI: 10.4161/cib.13550] [Citation(s) in RCA: 123] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
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7
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Jorgensen JS. Defining the neighborhoods that escort the oocyte through its early life events and into a functional follicle. Mol Reprod Dev 2013; 80:960-76. [PMID: 24105719 PMCID: PMC3980676 DOI: 10.1002/mrd.22232] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2013] [Accepted: 08/15/2013] [Indexed: 01/19/2023]
Abstract
The ovary functions to chaperone the most precious cargo for female individuals, the oocyte, thereby allowing the passage of genetic material to subsequent generations. Within the ovary, single oocytes are surrounded by a legion of granulosa cells inside each follicle. These two cell types depend upon one another to support follicle formation and oocyte survival. The infrastructure and events that work together to ultimately form these functional follicles within the ovary are unprecedented, given that the oocyte originates as a cell like all other neighboring cells within the embryo prior to gastrulation. This review discusses the journey of the germ cell in the context of the developing female mouse embryo, with a focus on specific signaling events and cell-cell interactions that escort the primordial germ cell as it is specified into the germ cell fate, migrates through the hindgut into the gonad, differentiates into an oocyte, and culminates upon formation of the primordial and then primary follicle.
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Affiliation(s)
- Joan S Jorgensen
- Department of Comparative Biosciences, University of Wisconsin, Madison, Wisconsin
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8
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Tanaka M. Vertebrate female germline--the acquisition of femaleness. WILEY INTERDISCIPLINARY REVIEWS-DEVELOPMENTAL BIOLOGY 2013; 3:231-8. [PMID: 24896659 DOI: 10.1002/wdev.131] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/18/2011] [Revised: 08/29/2013] [Accepted: 10/09/2013] [Indexed: 01/16/2023]
Abstract
The cellular and molecular characteristics of female germ cells have primarily been studied in the mammalian ovary. In most female mammals, all primordial germ cells (PGCs) develop into oocytes early during ovary formation, and germline stem cells are few in number or absent in postnatal ovaries (Lei L, Spradling AC. Female mice lack adult germ-line stem cells but sustain oogenesis using stable primordial follicles. Proc Natl Acad Sci USA 2013, 110:8585-8590). Research efforts in the field have largely focused on meiosis and follicular development, but a fundamental question regarding establishment of femaleness, which is very important to understand the 'female' germline, has not been discussed sufficiently. Recent work has revealed the presence of germline stem cells in the vertebrate ovary, using the teleost fish, medaka (Oryzias latipes) (Nakamura S, Kobayashi K, Nishimura T, Higashijima S, Tanaka, M. Identification of germline stem cells in the ovary of teleost medaka. Science 2010, 328:1561-1563). This discovery allows direct comparison between female and male germline stem cells and raises an interesting and heretofore unaddressed issue regarding femaleness of germline stem cells. In this article, the germ cell behavior in the ovaries of different species is reviewed and compared, the molecular mechanisms underlying the generation of female germ cells are discussed, and the relationship between female germ cells and the surrounding somatic cells is examined.
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Affiliation(s)
- Minoru Tanaka
- Laboratory of Molecular Genetics for Reproduction, National Institute for Basic Biology, Okazaki, Japan
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9
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Lechowska A, Bilinski SM, Rasweiler JJ, Cretekos CJ, Behringer RR, Kloc M. Early oogenesis in the short-tailed fruit bat Carollia perspicillata: transient germ cell cysts and noncanonical intercellular bridges. Genesis 2011; 50:18-27. [PMID: 21681920 DOI: 10.1002/dvg.20780] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2011] [Revised: 06/08/2011] [Accepted: 06/13/2011] [Indexed: 11/08/2022]
Abstract
The ovaries of early embryos (40 days post coitum/p.c.) of the bat Carollia perspicillata contain numerous germ-line cysts, which are composed of 10 to 12 sister germ cells (cystocytes). Variability in the number of cystocytes within the cyst and between the cysts (defying the Giardina rule) indicates that the mitotic divisions of the cystoblast are asynchronous in this bat species. Serial section analysis showed that the cystocytes are interconnected via intercellular bridges that are atypical, strongly elongated, short-lived, and rich in microtubule bundles and microfilaments. During slightly later stages of embryonic development (44-46 days p.c.), somatic cells penetrate the cyst, and their cytoplasmic projections separate individual oocytes. Separated oocytes surrounded by a single layer of somatic cells constitute the primordial ovarian follicles. The oocytes of C. perspicillata are similar to mouse oocytes and are asymmetric. In both species, this asymmetry is clearly recognizable in the localization of the Golgi complexes. The presence of germ-line cysts and intercellular bridges (although noncanonical) in the fetal ovaries of C. perspicillata suggest that the formation of germ-line cysts is an evolutionarily conserved phase in the development of the female gametes in a substantial part of the animal kingdom.
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10
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Haglund K, Nezis IP, Stenmark H. Structure and functions of stable intercellular bridges formed by incomplete cytokinesis during development. Commun Integr Biol 2011; 4:1-9. [PMID: 21509167 DOI: 10.4161/cib.4.1.13550] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/05/2010] [Accepted: 09/08/2010] [Indexed: 01/12/2023] Open
Abstract
Cytokinesis, the final step of cell division, normally proceeds to completion in living organisms, so that daughter cells physically separate by abscission. In certain tissues and developmental stages, on the other hand, the cytokinesis process is incomplete, giving rise to cells interconnected in syncytia by stable intercellular bridges. This evolutionarily conserved physiological process occurs in the female and male germline in species ranging from insects to humans, and has also been observed in some somatic tissues in invertebrates. Stable intercellular bridges have fascinated cell biologists ever since they were first described more than 50 years ago, and even though substantial progress has been made concerning their ultrastructure and molecular composition, much remains to be understood about their biological functions. Another major question is by which mechanisms complete versus incomplete cytokinesis is determined. In this mini-review we will try to give an overview of the current knowledge about the structure, composition and functions of stable intercellular bridges, and discuss recent insights into the molecular control of the incomplete cytokinesis process.
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Affiliation(s)
- Kaisa Haglund
- Department of Biochemistry; Institute for Cancer Research; Oslo University Hospital; Centre for Cancer Biomedicine; Faculty of Medicine; University of Oslo; Montebello, Oslo, Norway
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11
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Brubacher JL, Huebner E. Evolution and development of polarized germ cell cysts: new insights from a polychaete worm, Ophryotrocha labronica. Dev Biol 2011; 357:96-107. [PMID: 21726546 DOI: 10.1016/j.ydbio.2011.06.026] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Revised: 06/18/2011] [Accepted: 06/18/2011] [Indexed: 01/17/2023]
Abstract
Polarized oogenic cysts are clonal syncytia of germ cells in which some of the sister cells (cystocytes) differentiate not as oocytes, but instead as nurse cells: polyploid cells that support oocyte development. The intricate machinery required to establish and maintain divergent cell fates within a syncytium, and the importance of associated oocyte patterning for subsequent embryonic development, have made polarized cysts valuable subjects of study in developmental and cell biology. Nurse cell/oocyte specification is best understood in insects, particularly Drosophila melanogaster. However, polarized cysts have evolved independently in several other animal phyla. We describe the differentiation of female cystocytes in an annelid worm, the polychaete Ophryotrocha labronica. These worms are remarkable for their elegantly simple cysts, which comprise a single oocyte and nurse cell, making them an appealing complement to insects as subjects of study. To elucidate the process of cystocyte differentiation in O. labronica, we have constructed digital 3D models from electron micrographs of serially sectioned ovarian tissue. These models show that 2-cell cysts arise by fragmentation of larger "parental" cysts, rather than as independent units. The parental cysts vary in size and organization, are produced by asynchronous, indeterminate mitotic divisions of progenitor cystoblasts, and lack fusome-like organizing organelles. All of these characteristics represent key cytological differences from "typical" cyst development in insects like D. melanogaster. In light of such differences and the plasticity of female cyst structure among other animals, we suggest that it is time to reassess common views on the conservation of oogenic cysts and the importance of cysts in animal oogenesis generally.
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Affiliation(s)
- John L Brubacher
- Department of Biological Sciences, University of Manitoba, Winnipeg, MB, Canada.
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12
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Abstract
Despite its significant role in oocyte generation and hormone production in adulthood, the ovary, with regard to its formation, has received little attention compared to its male counterpart, the testis. With the exception of germ cells, which undergo a female-specific pattern of meiosis, morphological changes in the fetal ovary are subtle. Over the past 40 years, a number of hypotheses have been proposed for the organogenesis of the mammalian ovary. It was not until the turn of the millennium, thanks to the advancement of genetic and genomic approaches, that pathways for ovary organogenesis that consist of positive and negative regulators have started to emerge. Through the action of secreted factors (R-spondin1, WNT4, and follistatin) and transcription regulators (beta-catenin and FOXL2), the developmental fate of the somatic cells is directed toward ovarian, while testicular components are suppressed. In this chapter, we review the history of studying ovary organogenesis in mammals and present the most recent discoveries using the mouse as the model organism.
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Affiliation(s)
- Chia-Feng Liu
- Department of Veterinary Biosciences, University of Illinois at Urbana-Champaign, Illinois, USA
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13
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Abstract
A critical element of successful sexual reproduction is the generation of sexually dimorphic adult reproductive organs, the testis and ovary, which produce functional gametes. Examination of different vertebrate species shows that the adult gonad is remarkably similar in its morphology across different phylogenetic classes. Surprisingly, however, the cellular and molecular programs employed to create similar organs are not evolutionarily conserved. We highlight the mechanisms used by different vertebrate model systems to generate the somatic architecture necessary to support gametogenesis. In addition, we examine the different vertebrate patterns of germ cell migration from their site of origin to colonize the gonad and highlight their roles in sex-specific morphogenesis. We also discuss the plasticity of the adult gonad and consider how different genetic and environmental conditions can induce transitions between testis and ovary morphology.
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Affiliation(s)
- Tony DeFalco
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710
| | - Blanche Capel
- Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710
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14
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Grandi G, Chicca M. Histological and ultrastructural investigation of early gonad development and sex differentiation in Adriatic sturgeon (Acipenser naccarii, Acipenseriformes, Chondrostei). J Morphol 2008; 269:1238-62. [DOI: 10.1002/jmor.10657] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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15
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Pepling ME, Spradling AC. Mouse ovarian germ cell cysts undergo programmed breakdown to form primordial follicles. Dev Biol 2001; 234:339-51. [PMID: 11397004 DOI: 10.1006/dbio.2001.0269] [Citation(s) in RCA: 491] [Impact Index Per Article: 21.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
In many organisms, early germline development takes place within cysts of interconnected cells that form by incomplete cytokinesis and later undergo programmed breakdown. We recently identified similar cell clusters within the fetal mouse ovary, but the fate and functional significance of these germ cell cysts remained unclear. Here, we show that mouse cysts undergo programmed breakdown between 20.5-22.5 dpc, during which approximately 33% of the oocytes survive to form primordial follicles. This process accounts for most of the perinatal reduction in germ cell numbers and germ cell apoptosis reported by previous authors, and suggests that perinatal germ cell loss is a developmentally regulated process that is distinct from the follicular atresia that occurs during adult life. Our observations also suggest a novel function for a transient cyst stage of germ cell development. Prior to breakdown, mitochondria and ER reorganize into perinuclear aggregates, and can be seen within the ring canals joining adjacent germ cells. Cysts may ensure that oocytes destined to form primordial follicles acquire populations of functional mitochondria, through an active process that has been evolutionarily conserved.
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Affiliation(s)
- M E Pepling
- Howard Hughes Medical Institute Research Laboratories, Department of Embryology, Carnegie Institution of Washington, 115 W. University Parkway, Baltimore, Maryland 21210, USA
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16
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Abstract
Oocytes from many invertebrates initiate development within distinctive cysts of interconnected cells, which are formed through synchronous divisions of a progenitor cell. Recently, processes underlying cyst formation have been extensively characterized at the molecular level in Drosophila. Defects in this process cause sterility in female flies. Early female mouse germ cells are organized as cell clusters as well, but it is uncertain whether these groups are similar to the cysts of invertebrates. We find that mouse germ cells are connected by intercellular bridges in the ovaries of 11.5 to 17.5 days postcoitum embryos; microtubules and organelles have been observed within these bridges. Confocal microscopy shows that cells within mouse clusters divide synchronously and frequently correspond in number to powers of two. Thus, female mouse germ cell clusters exhibit key characteristics of invertebrate germline cysts indicating that the process of germline cyst formation is conserved in the mouse.
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Affiliation(s)
- M E Pepling
- Howard Hughes Medical Institute Research Laboratories, Department of Embryology, Carnegie Institution of Washington, Baltimore, MD 21210, USA
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17
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Abstract
Caspases, a class of cysteine proteases, are an essential component of the apoptotic cell death program. During Drosophila oogenesis, nurse cells transfer their cytoplasmic contents to developing oocytes and then die. Loss of function for the dcp-1 gene, which encodes a caspase, caused female sterility by inhibiting this transfer. dcp-1- nurse cells were defective in the cytoskeletal reorganization and nuclear breakdown that normally accompany this process. The dcp-1- phenotype suggests that the cytoskeletal and nuclear events in the nurse cells make use of the machinery normally associated with apoptosis and that apoptosis of the nurse cells is a necessary event for oocyte development.
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Affiliation(s)
- K McCall
- Howard Hughes Medical Institute, Department of Biology, 31 Ames Street, 68-430, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
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18
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Grandi G, Colombo G. Development and early differentiation of gonad in the european eel (Anguilla anguilla [L.], Anguilliformes, Teleostei): A cytological and ultrastructural study. J Morphol 1997; 231:195-216. [DOI: 10.1002/(sici)1097-4687(199702)231:2<195::aid-jmor8>3.0.co;2-d] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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19
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Tres LL, Rivkin E, Kierszenbaum AL. Sak 57, an intermediate filament keratin present in intercellular bridges of rat primary spermatocytes. Mol Reprod Dev 1996; 45:93-105. [PMID: 8873075 DOI: 10.1002/(sici)1098-2795(199609)45:1<93::aid-mrd13>3.0.co;2-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
We have previously reported the purification of Sak 57 (for spermatogenic cell/sperm-associated keratin of molecular mass 57 kDa) from outer dense fibers of rat sperm tails. Internal protein sequence analysis of Sak 57 revealed 70-100% homology to the 1A and 2A regions of the alpha-helical rod domain of human, mouse, and rat keratins. A multiple antigen peptide was synthesized using the KQYEDIAQK sequence corresponding to the 2A region and a polyclonal antibody was produced in rabbit to detect Sak 57. During spermiogenesis, Sak 57 associates with the microtubular manchette before becoming a component of para-axonemal keratin structures of the developing tail. We now report that during late meiotic prophase, intercellular bridges linking late pachytene-diplotene spermatocytes display a distinct ribbon containing a Sak 57/beta-tubulin complex, separated by a nonimmunoreactive midzone. Indirect immunofluorescence demonstrates that the ribbon is the final stage of a three-step developmental sequence: (1) a spindlelike arrangement radiating from equidistant spherical centers in early pachytene spermatocytes, (2) an ectoplasmic shell-like framework in mid-to-late pachytene spermatocytes, and (3) a Sak 57/beta-tubulin-containing ribbon found in intercellular bridges linking adjacent late pachytene-diplotene spermatocytes. Shear forces causing a breakdown of one of the conjoined spermatocytes do not disrupt the cytoskeletal ribbon. Results of this work, together with previous observations during spermiogenesis, show that Sak 57 associates with cytoplasmic microtubules in a timely fashion. Upon completion of late meiotic prophase, the Sak 57/microtubule complex behaves as an intercellular ligament and contributes to both the strength of intercellular bridges and the cohesiveness of members of a spermatocyte lineage.
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Affiliation(s)
- L L Tres
- Department of Cell Biology and Anatomical Sciences, City University of New York Medical School, New York 10031, USA
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20
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Liang LF, Dean J. Oocyte development: molecular biology of the zona pellucida. VITAMINS AND HORMONES 1993; 47:115-59. [PMID: 8447112 DOI: 10.1016/s0083-6729(08)60445-8] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/30/2023]
Affiliation(s)
- L F Liang
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health Bethesda, Maryland 20892
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21
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Andreuccetti P, Motta CM, Filosa S. Regulation of oocyte number during oocyte differentiation in the lizard Podarcis sicula. CELL DIFFERENTIATION AND DEVELOPMENT : THE OFFICIAL JOURNAL OF THE INTERNATIONAL SOCIETY OF DEVELOPMENTAL BIOLOGISTS 1990; 29:129-41. [PMID: 2322875 DOI: 10.1016/0922-3371(90)90066-6] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
This paper concerns the differentiation process of germ cells from oogonia to primary follicles in the lizard Podarcis sicula. The study was carried out at the morphological level and using a cytophotometric analysis for determining the number of differentiating germ cells undergoing degeneration. The progressive disorganization of the germ cell clusters during the early diplotene stage and the role played by the prefollicular cells during this process are described. Oocyte degeneration has been observed between the mid-zygotene and the early diplotene stages. When the primary follicle (oocyte plus follicular cells) is being formed, the degeneration process stops and the oocyte undergoes regular growth and ovulation.
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Affiliation(s)
- P Andreuccetti
- Department of Evolutive and Comparative Biology, Faculty of Science, University of Naples, Italy
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Spray DC, Cherbas L, Cherbas P, Morales EA, Carrow GM. Ionic coupling and mitotic synchrony of siblings in a Drosophila cell line. Exp Cell Res 1989; 184:509-17. [PMID: 2509224 DOI: 10.1016/0014-4827(89)90348-0] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Following mitosis in many cell lines, siblings remain adjoined in dyads until further cell division. We report here a series of experiments designed to ascertain the nature of this apposition in the embryonic Kc cell line of Drosophila melanogaster. We have found that (1) cell division in siblings is highly synchronized when compared to that in nonsiblings: (2) siblings in dyads are dye coupled with respect to Lucifer Yellow, but intercellular diffusion of larger molecules (FITC-dextran at 6 and 24 kDa) is retarded: (3) siblings are electrically coupled by an ungated low-resistance intercellular connection which is resistant to treatment with octanol and CO2, both known to close gap junction channels: and (4) members of a dyad are joined by a cytoplasmic bridge. Structures resembling septate junctions are also found between siblings and between cells in aggregates. The evidence accumulated here suggests that cytokinesis in Kc dyads is incomplete, resulting in an intercellular pathway that may provide for the passage of a molecular or electrical signal that regulates subsequent mitosis.
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Affiliation(s)
- D C Spray
- Marine Biological Laboratory, Woods Hole Massachusetts 02543
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Abstract
Recent reviews of the role of cell junctions in development have focused primarily upon functions related to the relatively subtle physiological modulation of their subunits in relation to fundamental developmental processes in a wide variety of organisms. There is, however, considerable support from numerous laboratories that the more radical modulation of the presence and number of junctional subunits in many diverse tissues may play a pivotal role in a wide spectrum of developmental phenomena ranging from gametogenesis to organogenesis. Since a great deal of recent interest in this latter subject has concentrated upon vertebrate systems including mammals, this review will examine the functional significance of the modulation of gap junctions, tight junctions and desmosomes in a developing idealized mammalian system from gamete formation to tissue and organ differentiation during embryo-genesis.
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Affiliation(s)
- W J Larsen
- Department of Anatomy and Cell Biology, University of Cincinnati College of Medicine, Ohio 45267-0521
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Affiliation(s)
- M De Felici
- Department of Anatomy and Cell Biology, II University of Rome, Italy
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McReynolds HD, Blanchet LJ, Bowman DC, Hakim AA, Kiely ML. Intercellular bridges in ovaries of the newborn gerbil. J Morphol 1984; 180:29-35. [PMID: 6726817 DOI: 10.1002/jmor.1051800105] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
This study describes intercellular bridges in the ovaries of neonatal gerbils. Electron microscopy has revealed the presence of true intercellular bridges, connecting oogonia or oocytes, in ovaries of newborn gerbils. The cytoplasm of the intercellular channels is similar to that of the connected cells, with mitochondria, smooth and rough endoplasmic reticulum, and free ribosomes present. Lysosomes are also occasionally present in the intercellular bridges and they may be involved in early waves of oocyte atresia. An electron-dense substance, 350-500 A thick, is located immediately beneath the unit membrane of the intercellular bridges. Accumulation of electron-dense material increases the thickness of the walls of the intercellular bridges, supporting and maintaining the patency of the channels. It is suggested that the intercellular channels probably allow the interchange of nutrients, organelles, and possibly regulatory materials as well.
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Zamboni L, Upadhyay S. Germ cell differentiation in mouse adrenal glands. THE JOURNAL OF EXPERIMENTAL ZOOLOGY 1983; 228:173-93. [PMID: 6663256 DOI: 10.1002/jez.1402280204] [Citation(s) in RCA: 125] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
The differentiation of germ cells in the adrenal glands of 26 male and female Swiss albino mice was studied in sequential stages of development, from day 12 1/2 of intrauterine life to postnatal day 21; the study was performed by means of high-resolution light microscopy and electron microscopy. In 12 1/2- and 13-day-old embryos, the ectopic cells had morphologic characteristics typical of primordial germ cells, whereas in 14- and 15-day-old fetuses they were identifiable as oogonia. In male and female fetuses from day 17 to term, all ectopic germinal elements entered meiotic prophase, reached diplotene, and differentiated into oocytes in perfect adherence to mouse ovarian timetables. In the postnatal animals, females as well as males, all oocytes progressed through the postmeiotic phase of growth just as they normally do in ovarian follicles, and, in the 2- and 3-week-old animals, they displayed features identical to those exhibited by oocytes in large antral follicles, including a zona pellucida. Germinal elements were no longer seen in the adrenals of animals older than 3 weeks. Our study shows that mammalian germ cells are capable of developing even outside the gonads, and that in ectopic sites they all differentiate as oocytes irrespective of their genetic sex.
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Tavassoli M, Shaklai M. Junctional structures in haemopoiesis: a study of bone marrow using freeze-fracture and lanthanum impregnation techniques. Br J Haematol 1979; 43:235-41. [PMID: 508632 DOI: 10.1111/j.1365-2141.1979.tb03746.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Intercellular regions of contact in the haemopoietic compartment of normal rat bone marrow were studied using freeze-fracture and lanthanum tracer techniques. Small adhering junctions (like desmosomes and their variants) were found between haemopoietic and stromal cells but tight, gap or septate junctions could not be identified. These findings are in agreement with the concept that extensive junctional structures may be inconsistent with orderly development of this transient cell system, preventing the delivery of mature cells into the circulation and resulting in ineffective haemopoiesis. Occasionally 'pinching off' of a portion of the cytoplasm of erythroid cells by stromal cells was seen, providing a means for intercellular communication. Structures similar to intercellular bridges responsible for direct intercellular communication were also seen.
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Trentini M, Scanabissi FS. Ultrastructural observations on the oogenesis of Triops cancriformis (Crustacea, Notostraca). Cell Tissue Res 1978; 194:71-7. [PMID: 719733 DOI: 10.1007/bf00209234] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Each ovarian follicle of Triops cancriformis is four-celled; these cells (one oocyte and three nurse cells) are interconnected by cytoplasmic bridges. In the course of differentiation, the nurse cells are clearly recognizable; they increase in size more than the oocyte and their nuclei contain many nucleoli. For the first time in Arthropoda, yolk globules are reported to be present in nurse cell cytoplasm; these globules arise from the smooth endoplasmic reticulum. The functional significance of the intercellular bridges and the trophic role of the nurse cells are discussed.
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Huckins C. Spermatogonial intercellular bridges in whole-mounted seminiferous tubules from normal and irradiated rodent testes. THE AMERICAN JOURNAL OF ANATOMY 1978; 153:97-121. [PMID: 707312 DOI: 10.1002/aja.1001530107] [Citation(s) in RCA: 58] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Whole-mounted seminiferous tubules from normal and irradiated rodent testes were examined by light microscopy. These studies reveal the presence of intercellular bridges in all classes of spermatogonia except for the new As stem cells. It was demonstrated that As stem cells divide to produce new As spermatogonia or paired daughter cells that are united by a cytoplasmic bridge. Evidence was given that all subsequent progeny of these paired A's up to and including the production of type B spermatogonia remain linked by cytoplasmic bridges in increasingly larger and more complex syncytial networks. It is proposed that the intercellular bridges mediate both differentiation and degeneration of spermatogonia. The maintenance of synchronous development within cohorts of spermatogonia is attributed to the bridges. Moreover, the fact that spermatogonia in both normal and irradiated testes degenerate in clusters is determined by the presence of intercellular bridges. Lastly, the integrity of the bridges appears essential for normal germ cell development.
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Guraya SS. Recent advances in the morphology, histochemistry, and biochemistry of the developing mammalian ovary. INTERNATIONAL REVIEW OF CYTOLOGY 1977; 51:49-131. [PMID: 338539 DOI: 10.1016/s0074-7696(08)60226-0] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/14/2022]
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Abstract
Study of the germinal epithelium in the adult lizard shows that the germ cells constitute clusters of synchronized cells interconnected by intercellular bridges. Such bridges interconnect oogonia as well as early meiotic prophase oocytes (zygo-pachitene). Besides true intercellular bridges in oocytes, there are plasma membrane interruptions forming large zones that ensure cytoplasmic continuity between adjacent cells. In early diplotene, germ cells are isolated. Later, during auxocytosis, when the polymorphic follicular epithelium around the oocyte starts differentiating, intercellular bridges appear between the follicle cells and oocyte. No relationship is observed between the intercellular bridges found in the germinal epithelium and those found between the follicle cells and oocyte.
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Eddy EM, Kahri AI. Cell association and surface features in cultures of juvenile rat seminiferous tubules. Anat Rec (Hoboken) 1976; 185:333-58. [PMID: 937739 DOI: 10.1002/ar.1091850307] [Citation(s) in RCA: 24] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/25/2022]
Abstract
Short pieces of seminiferous tubules from juvenile rats were grown in tissue culture and studied by phase contrast light microscopy while living and by transmission and scanning electron microscopy after fixation and appropriate processing. The pieces of tubules remodeled in vitro, with the original explant becoming surrounded closely by a sheet of epithelioid cells and more peripherally by elongate cells. The epithelioid cells were identifiable as Sertoli cells because of the presence of characteristic Sertoli-Sertoli cell junctions near their upper surface. The elongate cells were derived from peritubular tissues, but could not be specifically identified as to cell type. Clusters of stellate cells and of round cells were present on the upper surface of the Sertoli cell sheets, but not on the elongate cells or the bare floor of the culture dish. The stellate cells were spermatogonia and the round cells were spermatocytes, as identified by fine structural features. Intercellular bridges were maintained between germ cells in culture without being surrounded by processes of Sertoli cells. Rudimentary junctions were present between germ cells and Sertoli cells in culture. The shape of germ cells in vitro was the same as the shape in situ, indicating that shape is an inherent feature of germ cells and is not determined by surrounding Sertoli cells.
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Arnold JM. Intercellular bridges in somatic cells: cytoplasmic continuity of blastoderm cells of Loligo pealei. Differentiation 1974; 2:335-41. [PMID: 4442679 DOI: 10.1111/j.1432-0436.1974.tb00368.x] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Ogle TF. Effects of ACTH on organelle interrelationships in the corpus luteum of the pregnant deermouse. Cell Tissue Res 1974; 153:195-209. [PMID: 4374309 DOI: 10.1007/bf00226608] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Bou-Resli M. Ultrastructural studies on the intercellular bridges between the oocyte and follicle cells in the lizard Acanthodactylus scutellatus Hardyi. ZEITSCHRIFT FUR ANATOMIE UND ENTWICKLUNGSGESCHICHTE 1974; 143:239-54. [PMID: 4472524 DOI: 10.1007/bf00519868] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Abstract
Fluorescein-labeled rabbit serum globulin was injected into vitellogenic oocytes of the cecropia moth. Though the label spread throughout the ooplasm in less than 30 min, it was unable even after 2 h to cross the complex of intercellular bridges connecting the oocyte to its seven nurse cells. After injection into a single nurse cell, fluorescence was detected in the oocyte adjacent to the bridge complex within 3 min and had spread throughout the ooplasm in 30 min. Here also, the cell bodies of the six uninjected nurse cells remained nonfluorescent. Four of the nurse cells are not bridged directly to the oocyte but only through the apical ends of their siblings. Unidirectional movement must therefore occur in the apical cytoplasm of the nurse cells, as well as in the intercellular bridges. The nurse cells of healthy follicles had an intracellular electrical potential -40 mV relative to blood or dissecting solution, while oocytes measured -30 mV. A mV difference was also detected by direct comparison between a ground electrode in one cell and a recording electrode in the other. Three conditions were found in which the 10 mV difference was reduced or reversed in polarity. In all three cases fluorescent globulin was able in some degree to cross the bridges from the oocyte to the nurse cells.
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Dyer RF, Ruby JR, Skalko RG. Ultrastructural observations on membranous structures in developing mouse oocytes. ZEITSCHRIFT FUR ZELLFORSCHUNG UND MIKROSKOPISCHE ANATOMIE (VIENNA, AUSTRIA : 1948) 1973; 137:159-66. [PMID: 4692956 DOI: 10.1007/bf00307427] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Bielanska-Osuchowska Z. Oogonia and oocytes degeneration and the nutritive macrophages in the process of the development of the ovary in embryos of the domestic pig (Sus scrofa dom. L.). ZEITSCHRIFT FUR ANATOMIE UND ENTWICKLUNGSGESCHICHTE 1973; 142:37-52. [PMID: 4768758 DOI: 10.1007/bf00519875] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/12/2023]
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McNutt NS, Weinstein RS. Membrane ultrastructure at mammalian intercellular junctions. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 1973; 26:45-101. [PMID: 4122630 DOI: 10.1016/0079-6107(73)90017-5] [Citation(s) in RCA: 268] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
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Ruby JR, Webster RM. Origin of the Golgi complex in germ cells in the developing ovary of the bat. ZEITSCHRIFT FUR ZELLFORSCHUNG UND MIKROSKOPISCHE ANATOMIE (VIENNA, AUSTRIA : 1948) 1972; 133:1-12. [PMID: 4343120 DOI: 10.1007/bf00307063] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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Skalko RG, Kerrigan JM, Ruby JR, Dyer RF. Intercellular bridges between oocytes in the chicken ovary. ZEITSCHRIFT FUR ZELLFORSCHUNG UND MIKROSKOPISCHE ANATOMIE (VIENNA, AUSTRIA : 1948) 1972; 128:31-41. [PMID: 5021446 DOI: 10.1007/bf00306886] [Citation(s) in RCA: 26] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Clérot JC. [Intercellular bridges in the testis of Gardonus: syncitial organization and synchrony in the differentiation of germ cells]. JOURNAL OF ULTRASTRUCTURE RESEARCH 1971; 37:690-703. [PMID: 5167540 DOI: 10.1016/s0022-5320(71)80032-1] [Citation(s) in RCA: 25] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
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Neaves WB. Intercellular bridges between follicle cells and oocyte in the lizard, Anolis carolinensis. Anat Rec (Hoboken) 1971; 170:285-301. [PMID: 5088401 DOI: 10.1002/ar.1091700305] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Bentfeld ME. Studies of oogenesis in the rotifer, Asplanchna. II. Oocyte growth and development. ZEITSCHRIFT FUR ZELLFORSCHUNG UND MIKROSKOPISCHE ANATOMIE (VIENNA, AUSTRIA : 1948) 1971; 115:184-95. [PMID: 5573595 DOI: 10.1007/bf00391124] [Citation(s) in RCA: 22] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Ovarian intercellular bridges in Dermacentor andersoni stiles (acari: ixodidae). Tissue Cell 1971; 3:615-22. [DOI: 10.1016/s0040-8166(71)80008-3] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/1971] [Indexed: 11/19/2022]
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Ruby JR, Dyer RF, Skalko RG, Volpe EP. Intercellular bridges between germ cells in the developing ovary of the tadpole, Rana pipiens. Anat Rec (Hoboken) 1970; 167:1-9. [PMID: 5447366 DOI: 10.1002/ar.1091670102] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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The ultrastructure of the developing leg ofDrosophila melanogaster. Dev Genes Evol 1970; 166:1-44. [DOI: 10.1007/bf00576805] [Citation(s) in RCA: 159] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/25/1970] [Indexed: 10/26/2022]
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