Touch Mss
Posted on Saturday, November 7th, 2009 at 10:33 am
Gap juctions,oocyte development nueral tube defects
Gap Function and Oocyte Development
Primodial germ cell number millions at birth. They are known to be in clusters which breaks down to form primodial follicle. As defined earlier primodial follicle is flattened germ cell encasing oocyte. A communication system exists between oocyte and surrounding germ cell or granulosa cells the signal transfer occurs via gap junctions of the somatic and germ cell. Nutrient exchange is also facilitated by these gap junctions. This communication mechanism is made up of comexin family of proteins.
Their expression is specific to granulosa cell differentiation and expression. Is it this communication system which activates the follicular and oocyte growth and development. Does it exist before puberty. These are some of the questions needing answer. Possible explanation have come from the research investigations of Fair, 2003 from Dublin, Irish Institute. He has C-Kit receptor and its Lignad, IGF-I, IGF-I receptors and IGF binding proteins alongwith transforming growth factor beta (TGF beta) family responsible for the activation of primodial follicles. The bone morphogenetic proteins do play a role right from oogenesis to ovulation as demonstrated by Fair, 2003. the progressive structural rearrangements of oocytes facilitate a new wave of energy which triggers synthesis of nucleic acid. It is clear here that oocyte need a wave of energy to boost or initiate it activity. Does it mean the same energy as referred “Rouh” in Quran narrating and explaining birth of “Jesus Christ,” through a wave of energy, rather than any physical touch or contact. Perhaps at this movement of our understanding it is clear the “Wave of Activation” is of importance in giving “Wake Up Cells” to dormant oocyte or ovum when shed. It is this energy activation which triggers nuclear activity after fertilization. The meiotic and embryo development competence is ascribed to this wave of energy. Some of the Fairs experiences in-vivo have been mimic in-vitro too with success. The control of growth and factors responsible for generating this “wave of nuclear energy” hidden within a 30-200 µm oocyte is still partially known. Once the unknown become known, the science may give more explanation beyond the known factors responsible for giving development competence to the oocyte.
During follicular development in hen Mitogen-Activate protein (MAP) Kinase signaling induced by transforming growth factor Alpha (TGF alpha) blocks FSH-induced differentiation. In other words MAP block FSH induced differentiation in granulosa cells of hen egg. Does a similar factors prevents monolayerd granulosa cells to be responsive to FSH. This needs further research. Johson et al. 2002 has demonstrated. Similarly, the steroidogenic acute regulatory proteins (StAR) is blocked. Inviva studies of Johson et al, 2002 confirmed the postulation.
Rapid transcription and translation of StAR, P-450 cholesterol side-chain enzymes accelerates progesterone secretion from granulosa cells after LH treatment. The explanation cited by the authors are wanting more details as presently identified factors alone are not able to explain the signaling pathways of preovulatory follicles.
Development of follicles using genomic methylation studies reveal that genomic methylation patters originate during gametogenesis and are responsible for gene regulation, embryogenesis and genome imprinting. The mitotic, meiotic development is blocked by 5-azacytidine addition. The drug blocks DNA methylation. Does such effect seen during spermatogenesis repeat in oogenesis too needs discussion. Doerksen et al. 2000.
IV. Zona-Pellucida Formation
Zona-pellucida is formed during the process of folliculogenesis. Department of Anatomy, cell Biology laboratory of health science, Queen’s University Canada has investigated the subcellular distribution of ZPI zona-pellucida 1,2 and 3 glycoproteins during folliculogenesis (Mestrah et al, 2002). Zona pellucida (ZP) is an extra cellular coat synthesized by oocyte during development. A new technique using antibodies against on intracellular material trafficking from oocyte for synthesize Zona-pellucida. We have mentioned earlier that radio-opaque granules migrate from oocyte cytoplasm to its periphery, which ultimately give rise to a glycoprotein layer called Zona-pellucida.
This study has demonstrated the role of Golgi Apparatus, secretory granules and vesicular aggregates in mouse oocyte in Zona-pellucida synthesis. The mechanism of matrix formation and stoichiometric disposition of ZP1, ZP2, & ZP3 in mouse oocyte development has been investigated (Mestrah et al, 2002).
The actions of insulin like growth factors (IGF-I) on rabbit ovarian cells has been investigate4d. progesterone secretion was stimulated by injecting dose of 1 ng/ml of IGF-I, in granulosa cells culture media. The higher doses of 10 ng and 100 ng were inhibiting the progesterone secretions. IGF-I did not effect oestradiol secretion in this study. Cyclic AMP secretion increased slightly with addition of 10 ng IGF-I in the culture but not by higher concentrations.
Blocker of proteinkinase A, Rp-cAMPs did not alter progesterone or estrogen secretion by the rabbit granulos cell culture. However, the action of IGF-I vis-in-vis progesterone secretion was altered. Many details of the mechanism of action of IGF-I, II & III was discussed and new biochemical players were identified. Immuno- cyto chemical technique to study these effects were described (Makarevich et al. 2000). This study conduct in Solvakia demonstrates a high level of scientific competence at Research Institute of Animal Production, Hlohovska 2, 94992 Nitra, Slovakia. The search was published in reputed Journal of steroid Biochemistry and Molecular Biology 73 (314) : 123-133 giving reference to about 46 scientific publications in this field. More studies on Bovine, Ovine or human granulosa cells may further clarify the stagnancy and dormancy of the ovarian follicles at menopause or before puberty.
Epidermal growth factor (EGF) and IGF-I have a role to play in folliculogeneis in pigs. This was the object of investigation by Mao et al, 2004 at Columbia, USA. The regulation of preantral follicular formation, antrum formation and granulosa cell development was investigated under the influence of EGF &IF-I co-cultures. The media used for culture were Waymouths, Alpha-minimum Eagles essential media, supplemented with 10 micro g/ml transferring or 100 micro g/ml L-ascarbic acid and 2 m v/ml ovine FSH. Use of IGF-I enhanced granulosa cell proliferation follicular integrity and recovery of oocyte-cumulus oophrus complexes. There was low apoptosis (cell-death) higher IGF-I doses 100 micro gram/ml were regarded better than lower doses. IGF-I was added in three proportions 1, 50, 10, 1000 ng/ml in different experimental groups. Epidermal growth factors were seen to reduce folliculogenesis when given above. However, combination of IGF-I and EGF increased granulosa cell proliferation, decreased apoptosis and promoted follicular antrum formation. Use of IGF-I and EGF in invitro maturation of mammalian oocyte may help to increase benefits of the (ART) assisted reproductive techniques in women. The alpha-minimum Eagles medium in combination or without IGF-I addition did not compare well with other medias discussed in the protocol. The students may refer the original work of Mao for use of these media. The work was published in Journal of Animal Science 2004, 82 (7) : 1967-1975 during 2004. the email contact of co-author is dayb@missouri.edu .
The effects of ammonium chloride on the growth and metabolism of bovine granulosa cells and the development of ovine oocytes matured in the presence of bovine granulosa cells previously exposed to ammonium sulphate was studies in UK by Rooke et al, 2004. The results published in Animal Reproduction Science 84 (1/2) : 53-71 indicate that invitro growth and metabolism of granulosa cells were altered in presence of ammonium chloride (NH4Cl). The effects were irreversible. Similarly, granulosa cells conditioned with ammonium chloride impaired maturation of ovine oocytes.
Ovine ooplasm directs initial initial nucleolar assembly in embryo cloned from ovine, bovine and porcine cells. A study in Australia published in Molecular Reproduction and Development 2004 in rol 69 (2) : 117-125 by Hamilton, H.M, Peura, TT, Laurincik, J, Walker, SK, Maddocks, S, Maddox-Hytel, P gave details of ultra structural and immunocytochemical evidence that ovine ooplasm a directs initial assembly of the nucleolus. Somatic cell nuclear transfer (SCNT) revealed that ovine ooplasm played a role in initial assembly of the embryonic nucleolus in intra generic SCNT embryo. The study revealed that porcine-ovine SCNT embryos had cytoplasmic organelles in nucleus. The ovine-ovine SCNT embryo had fibrillo-granular nucleoli in 16 cell stage and Bovine-ovine SCNT embryo at 8 cell stage exhibited ruminant-type NPBs as well as fibrillar materials.
For more details refer (Wani, 2008, 2009) or the cited reference or their authors. No responsibility of any protocol or material referred to in these pages vest with editor, author or publisher. The readers are advised to examine accurate details of procedures, methods, techniques and materials from the concerned agencies cited as reference.
Our aim is to present basis and experimental details in principle and do not advocate any protocol, treatment, equipment, media, chemical or hormone. We have avoided use of company names, however, if somewhere even generic name confirm to any firm or company, details be sought before replicating or treating an ailment.
Reproductive Generic Techniques
Introduction
DNA: Is deoxyribose nucleic acid. This small cellular portion contains all information required to synthesize cellular and extra-cellular structure. A DNA is a double strand structure. Each strand of DNA consists of nucleotide units which are arranged in a linear polymer. The units are connected with pentose sugar at 5 carbon unit to a phosphate group and via its 1 carbon to one of the four bases Guaine, cytosine adenine, and thymine. The bases are arranged by the principles of Watson-Crick Base-Pairing Systems where Guanine base has purine base type and has 2 rings 3 hydrogen bond and base pair designated as G-C cytosine base has pyrimidine base type 3 hydrogen bonds and G-C base pair Adenine has purine base type 2 rings and hydrogen bonds but base pair is A-T which is similar to thymine who has pyrimidine as base type, one ring and 2 hydrogen bond. With this simples description of DNA readers are expected to read some fundamental molecular biology book to understand this chapter fully in its further elucidations. One copy of the entire double-stranded DNA content is referred to as haploid genome in humans. It has thus 3 x 109 base pairs in 23 separate molecules. Each cell is diploid with two copies of this genome in 46 chromosomes (22 pairs of autosomes and one pair of sex chromosomes) thus, every DNA strand or chromosome has a capacity to store enormous information both in autosomes and sex chromosome units.
Besides this vast information DNA contains scaffold chromatin which packages DNA with histones. The DNA not used by cell in template remains in an merit state tightly packaged within the chromatin scaffold of the chromosome. Thus, the usual function of any cell can be utilized to enfold this vast information. Once we understand and use this chromatin scaffold, a new generation of human and mammalian genetic techniques shall come into being. The cure, repairing diseases and will be easy ailment at genomic level. A new understanding of genetic applications are thus in offering in future. This chapter shall endeavor to propose a few known techniques in use at present in mammals.
Genetics Reproduction
New techniques such as invitrofertilization, IVF, pre-implantation, genetic diagnosis (PGD) and prenatal diagnosis shall be our focus in this section. The medical reproductive genetics techniques presently available can be enumerated as ;
a) Maternal Serum Screening: This technique called (BUN) is useful in detecting foetus likely to be effected with down syndrome. A serum test between 10-14 weeks of gestation helps to detect the disease. BUN study involves the measurement PAPP-A (Pregnancy Associated Plasma Protein) PAPP-A and free B-hcG (Human Chrorionic gonadotrophins with muchal translucently thickness.
b) Genetic Analysis of Fetal Cells: This technique allows to differentiate between fetal and maternal cells during pregnancy and helps to isolate single fetal cells for genetic manipulation or disease cure. Chromosome analysis can also be made on these fetal cells.
c) Aminocentesis (EATA): Easly removal of amniotic fluid between 13-16 weeks of pregnancy helps to diagnosis of various cell type and diagnosis of disease of neonate.
d) Many other techniques like maternal serum markers, in utero magnetic resonance imaging, preimplantation genetic diagnosis are being performed at present. The result obtained by such reproduction genetic techniques in the past shall be discussed.
e) Stem cell, cloning and ART assisted reproductive techniques are also in use with ethical restriction in humans
f) Research on Epigenetic process is also initiated
g) Use of genetic techniques for predetermining the capacity and capabilities of primodial germ cell containing oocyte shall be focus of future genetic engineering experts. While we shall review the earlier 7 set of technique in use at present. The last postulations shall help young genetic to unveil the potentialities of oocyte.
1. Material Serum Screening
Material Serum Screening is a blood test (MSS). This helps to determine certain abnormalities in the foetus. It is done in the first part of pregnancy. Generally it is done during first trimester of pregnancy in women. However, it can be also done in 2nd trimester of the pregnancy too. The following syndromes can be detected by this test. (1) Down Syndrome
It is also known as trisomy 21, because of the baby in women caries 3 copies of chromosome 21 instead of usual two. Downs Syndrome is associated with defects like intellectual impairment, heart abnormalities etc.
2. Edwards Syndrome
also known as trisomy 18. it occurs when foetus has three copies of chromosomes 18 instead of usual 2. Defects include neural deformity of hands and feet and intellectual impairment.
Neural Tube Defects
These are detected during 2nd trimester. Neural tube defects result in failure of the brain and spinal cord eg. Spina bifida, i.e. incomplete bifurcation of spinal vertebrae. Spinal cord and tube protudes through the gap instead growing down into the abdominal organs and legs leading to paralysis of the legs.
These are preliminary tests more precise and accurate diagnostic test to diagnose these syndromes are provided by Amniocentesis or Chorionic villi screening material serum screening can be coupled with nuchal translucency detected at ultrasonography around 12 weeks of pregnancy, where pocket of fluid at the back of neck of the foetus can be detected.
The best judge to advise patients is her doctor. However, these tests indicate risk factors and can not be taken as definitive. This has necessitated genetic counseling. The modern technique of prenatal genetic counseling and evaluation has become important to rescue mothers of the mental agony. Should
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