Polyspermy describes an egg that has been fertilized by more than one sperm. Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspermy
The first issue that an egg and a sperm of any organism type face in successfully producing an embryo is the possibility of polyspermy. Polyspermy is the fertilization of an egg by multiple sperm, and the results of such unions are lethal.
If multiple sperm fertilize an egg, the embryo inherits multiple paternal centrioles. This causes competition for extra chromosomes and results in the disruption of the creation of the cleavage furrow, thus causing the zygote to die. As an important model organism in the study of fertilization and embryonic development, polyspermy in sea urchins has been studied in detail. The sea urchin’s methods of polyspermy prevention have been broken down into two main pathways. These two primary pathways are known as the fast block and the slow block to polyspermy
After the sperm’s receptors come into contact with the egg’s jelly layer and the acrosomal enzymes are released and break down the jelly layer, the sperm head comes into contact with the vitelline and plasma membranes of the egg. When the two plasma membranes contact one another, signals in the egg are initiated.
First, Na+ channels in the egg open, allowing Na+ to flood into the egg. This causes a depolarization of the egg from it’s normal resting potential of -70 mV.
While depolarization is occurring, the remainder of the jelly layer is dissolving. With the dissolution of the jelly layer and the depolarization of the plasma membrane, the first block to preventing fertilization by multiple sperm is put into place.
These two simple changes are part of the first block to polyspermy, known as the fast block. Within 1/10th of a second of contact, the fast block t
The term implantation is used to describe the attachment of the developing embryo to the endometrium.
After fertilization, the embryo reaches the uterus in the blastocyst stage. Then attached to the wall of the uterus. Though the implantation may occur at any period between the sixth to the tenth day after the fertilization generally it occurs on the seventh day after fertilization.
Polyspermy describes an egg that has been fertilized by more than one sperm. Diploid organisms normally contain two copies of each chromosome, one from each parent. The cell resulting from polyspermy
The first issue that an egg and a sperm of any organism type face in successfully producing an embryo is the possibility of polyspermy. Polyspermy is the fertilization of an egg by multiple sperm, and the results of such unions are lethal.
If multiple sperm fertilize an egg, the embryo inherits multiple paternal centrioles. This causes competition for extra chromosomes and results in the disruption of the creation of the cleavage furrow, thus causing the zygote to die. As an important model organism in the study of fertilization and embryonic development, polyspermy in sea urchins has been studied in detail. The sea urchin’s methods of polyspermy prevention have been broken down into two main pathways. These two primary pathways are known as the fast block and the slow block to polyspermy
After the sperm’s receptors come into contact with the egg’s jelly layer and the acrosomal enzymes are released and break down the jelly layer, the sperm head comes into contact with the vitelline and plasma membranes of the egg. When the two plasma membranes contact one another, signals in the egg are initiated.
First, Na+ channels in the egg open, allowing Na+ to flood into the egg. This causes a depolarization of the egg from it’s normal resting potential of -70 mV.
While depolarization is occurring, the remainder of the jelly layer is dissolving. With the dissolution of the jelly layer and the depolarization of the plasma membrane, the first block to preventing fertilization by multiple sperm is put into place.
These two simple changes are part of the first block to polyspermy, known as the fast block. Within 1/10th of a second of contact, the fast block t
The term implantation is used to describe the attachment of the developing embryo to the endometrium.
After fertilization, the embryo reaches the uterus in the blastocyst stage. Then attached to the wall of the uterus. Though the implantation may occur at any period between the sixth to the tenth day after the fertilization generally it occurs on the seventh day after fertilization.
presentation on oogenesis of fertilisation process full details about it u will never find it anywhere else have full details about the ovum formation polar bodies and everything . so explore here
Development of gonads (Gonad differentiation)male gonad and female gonadshallu kotwal
The development of the gonads is part of the prenatal development of the reproductive system and ultimately forms the testes in males and the ovaries in females. The gonads initially develop from the mesothelial layer of the peritoneum.
Here provided contents for learning that what are the male and female gametes. How to they form? And described how to both gametes fused (fertilization)on the molecular basis.
In testis, the immature male germ cell (spermatogonia ) produce sperms by spermatogenesis
The spermatogonia ( sing. Spermatogonium ) present on the inside of seminiferous tubules multiply by mitotic division and increase in numbers
Each spermatogonium is diploid and contains 46 chromosomes
Some of the spermatogonia called primary spermatocytes periodically undergo meiosis.A primary spermatocyte completes the first meiotic division (reduction division) leading to formation of two equal, haploid cells called secondary spermatocyte, which have only 23 chromosomes
The secondary spermatocyte undergo the second meiotic division to produce four equal, haploid spermatids
How 3 germ layers are formed in Chick that are endoderm, mesoderm and ectoderm.As Chick are polylecithal so cell movements are somewhat restricted and gastrulation is modified as compared to frog.
A brief account of different parts of sperm and its constitutions and,ovum parts and different envelops.all things are explained by a simple attractive diagram.
Vittelogenesis is a word developed from Latin vitellus-yolk, and genero-produce
Vitellogenesis (also known as yolk deposition) is the process of yolk formation via nutrients being deposited in the oocyte, or female germ cell involved in reproduction of lecithotrophic organisms. In insects, it starts when the fat body stimulates the release of juvenile hormones and produces vitellogenin protein.
Yolks is the most usual form of food storage in the egg.
Yolks appear in the oocyte in the secondary period of their growth called vittelogenesis.
Thus,the formation and deposition of yolks is known as vittelogenesis
Characteristic
Yolks is a complex variable assembled component.
The principle component are protein,phospholipid and fats in different combination.
Depending upon these component yolks is distinguished into protein yolks and fatty acid
For eg- the avian contain 48.19% water , 16.6 % protein, 32.6% phospholipids and fats and 1% carbohydrates.
1. Spermatogenesis (Spermatocytogenesis, Spermiogenesis, Spermiation, Shape and function of cells inside the Testis, Semen and sperm structure, Sperm journey after synthesis to outside)
presentation on oogenesis of fertilisation process full details about it u will never find it anywhere else have full details about the ovum formation polar bodies and everything . so explore here
Development of gonads (Gonad differentiation)male gonad and female gonadshallu kotwal
The development of the gonads is part of the prenatal development of the reproductive system and ultimately forms the testes in males and the ovaries in females. The gonads initially develop from the mesothelial layer of the peritoneum.
Here provided contents for learning that what are the male and female gametes. How to they form? And described how to both gametes fused (fertilization)on the molecular basis.
In testis, the immature male germ cell (spermatogonia ) produce sperms by spermatogenesis
The spermatogonia ( sing. Spermatogonium ) present on the inside of seminiferous tubules multiply by mitotic division and increase in numbers
Each spermatogonium is diploid and contains 46 chromosomes
Some of the spermatogonia called primary spermatocytes periodically undergo meiosis.A primary spermatocyte completes the first meiotic division (reduction division) leading to formation of two equal, haploid cells called secondary spermatocyte, which have only 23 chromosomes
The secondary spermatocyte undergo the second meiotic division to produce four equal, haploid spermatids
How 3 germ layers are formed in Chick that are endoderm, mesoderm and ectoderm.As Chick are polylecithal so cell movements are somewhat restricted and gastrulation is modified as compared to frog.
A brief account of different parts of sperm and its constitutions and,ovum parts and different envelops.all things are explained by a simple attractive diagram.
Vittelogenesis is a word developed from Latin vitellus-yolk, and genero-produce
Vitellogenesis (also known as yolk deposition) is the process of yolk formation via nutrients being deposited in the oocyte, or female germ cell involved in reproduction of lecithotrophic organisms. In insects, it starts when the fat body stimulates the release of juvenile hormones and produces vitellogenin protein.
Yolks is the most usual form of food storage in the egg.
Yolks appear in the oocyte in the secondary period of their growth called vittelogenesis.
Thus,the formation and deposition of yolks is known as vittelogenesis
Characteristic
Yolks is a complex variable assembled component.
The principle component are protein,phospholipid and fats in different combination.
Depending upon these component yolks is distinguished into protein yolks and fatty acid
For eg- the avian contain 48.19% water , 16.6 % protein, 32.6% phospholipids and fats and 1% carbohydrates.
1. Spermatogenesis (Spermatocytogenesis, Spermiogenesis, Spermiation, Shape and function of cells inside the Testis, Semen and sperm structure, Sperm journey after synthesis to outside)
Located outside the abdominal cavity within a pouch called scrotum.
Scrotum provides low temperature required for spermatogenesis.
Each testis is about 4 to 5 cm length and 2 to 3 cm width.
Each testis has about 250 compartments called testicular lobules.
Each lobule contains one to three seminiferous tubules.
Seminiferous tubules lined by male germ cells and Sertoli cells.
Male germ cell undergoes meiosis and produce sperm.
Sertoli cells provide nutrition to the germ cell and the sperm.
In between the seminiferous tubule there is interstitial cell or Leydig
cell.
Leydig cells produce testicular hormones
called androgen (testosteron It is the primary female sex organs that produce the female
gamete (ovum).
It also produces several steroid hormones.
The ovaries located in the lower abdomen.
Each ovary is about 2-4 cm in length.
Connected to the pelvic wall and uterus by ligaments.
Each ovary is covered by thin epithelium which encloses the
ovarian stroma
The ovarian stroma has two zones
A peripheral cortex.
An inner medulla.
Comparing Evolved Extractive Text Summary Scores of Bidirectional Encoder Rep...University of Maribor
Slides from:
11th International Conference on Electrical, Electronics and Computer Engineering (IcETRAN), Niš, 3-6 June 2024
Track: Artificial Intelligence
https://www.etran.rs/2024/en/home-english/
(May 29th, 2024) Advancements in Intravital Microscopy- Insights for Preclini...Scintica Instrumentation
Intravital microscopy (IVM) is a powerful tool utilized to study cellular behavior over time and space in vivo. Much of our understanding of cell biology has been accomplished using various in vitro and ex vivo methods; however, these studies do not necessarily reflect the natural dynamics of biological processes. Unlike traditional cell culture or fixed tissue imaging, IVM allows for the ultra-fast high-resolution imaging of cellular processes over time and space and were studied in its natural environment. Real-time visualization of biological processes in the context of an intact organism helps maintain physiological relevance and provide insights into the progression of disease, response to treatments or developmental processes.
In this webinar we give an overview of advanced applications of the IVM system in preclinical research. IVIM technology is a provider of all-in-one intravital microscopy systems and solutions optimized for in vivo imaging of live animal models at sub-micron resolution. The system’s unique features and user-friendly software enables researchers to probe fast dynamic biological processes such as immune cell tracking, cell-cell interaction as well as vascularization and tumor metastasis with exceptional detail. This webinar will also give an overview of IVM being utilized in drug development, offering a view into the intricate interaction between drugs/nanoparticles and tissues in vivo and allows for the evaluation of therapeutic intervention in a variety of tissues and organs. This interdisciplinary collaboration continues to drive the advancements of novel therapeutic strategies.
Multi-source connectivity as the driver of solar wind variability in the heli...Sérgio Sacani
The ambient solar wind that flls the heliosphere originates from multiple
sources in the solar corona and is highly structured. It is often described
as high-speed, relatively homogeneous, plasma streams from coronal
holes and slow-speed, highly variable, streams whose source regions are
under debate. A key goal of ESA/NASA’s Solar Orbiter mission is to identify
solar wind sources and understand what drives the complexity seen in the
heliosphere. By combining magnetic feld modelling and spectroscopic
techniques with high-resolution observations and measurements, we show
that the solar wind variability detected in situ by Solar Orbiter in March
2022 is driven by spatio-temporal changes in the magnetic connectivity to
multiple sources in the solar atmosphere. The magnetic feld footpoints
connected to the spacecraft moved from the boundaries of a coronal hole
to one active region (12961) and then across to another region (12957). This
is refected in the in situ measurements, which show the transition from fast
to highly Alfvénic then to slow solar wind that is disrupted by the arrival of
a coronal mass ejection. Our results describe solar wind variability at 0.5 au
but are applicable to near-Earth observatories.
THE IMPORTANCE OF MARTIAN ATMOSPHERE SAMPLE RETURN.Sérgio Sacani
The return of a sample of near-surface atmosphere from Mars would facilitate answers to several first-order science questions surrounding the formation and evolution of the planet. One of the important aspects of terrestrial planet formation in general is the role that primary atmospheres played in influencing the chemistry and structure of the planets and their antecedents. Studies of the martian atmosphere can be used to investigate the role of a primary atmosphere in its history. Atmosphere samples would also inform our understanding of the near-surface chemistry of the planet, and ultimately the prospects for life. High-precision isotopic analyses of constituent gases are needed to address these questions, requiring that the analyses are made on returned samples rather than in situ.
A brief information about the SCOP protein database used in bioinformatics.
The Structural Classification of Proteins (SCOP) database is a comprehensive and authoritative resource for the structural and evolutionary relationships of proteins. It provides a detailed and curated classification of protein structures, grouping them into families, superfamilies, and folds based on their structural and sequence similarities.
2. Gametogenesis
Gametogenesis is the process of formation and differentiation of haploid gametes (sperms
and ova) from the diploid primary germ cells, gametogonia (spermatogonia and oogonia)
present in primary sex organs called gonads (testis in male and ovaries in female
respectively).
or
It is the process of formation of respective gametes (sperm and ova) in respective gonads.
It involves Spermatogenesis and Oogenesis.
3. Spermatogenesis
It is the process of formation of sperm in testis.
Testis: it is the primary male reproductive organ.
Shape and size: pinkish oval bodies occurring in
pair, size is about 4.5cm long, 2.5 cm wide and 3
cm thick.
Location: situated outside of abdominal cavity in
scrotal sac. (Temperature of 2-3°C below body
temperature is required for spermatogenesis)
Each testis is surrounded by three layers.
1. Tunical vaginalis: double membrane outer
covering, made up of fibrous connective tissue.
2. Tunica albuginea: it is the middle layer below
the tunica vaginalis.
3.Tunica vasculosa: it is the inner most highly
vascular layer with network of blood capillaries.
Histology of testis:
Each testis consists of 200-300 lobules, and each
lobule contains 1-4 convoluted loops called
Seminiferous tubules. In between the
seminiferous tubules, there is a group of
interstitial cell called Leydig cell, which secrete
testosterone, a male sex hormone. Each
seminiferous tubules lined with germinal
epithelium produce sperm by the
process Spermatogenesis.
4. Spermatogenesis occur in three
phase
i) Multiplication phase: the
germinal epithelium of seminiferous
tubules produce primordial germ
cell. These cell multiplies repeatedly
by mitosis to produce large number
of spermatogonia.
ii) Growth or Maturation
phase: The spermatogonia
undergoes maturation. It is a diploid
cell. After maturation
spermatogonia is known as Sperm
mother cell because it will
eventually develop into the mature
sperm.
5. iii) Meiotic phase:
Duplication of homologous
chromosome in sperm mother cell
occur and become ready for
meiosis. First meiotic division
produce two Primary
spermatocyte with haploid number
of chromosome. The first meiotic
division separates the homologous
chromosomes from each parent.
The second meiotic division of each
primary spermatocytes occur
resulting altogether of 4
haploid secondary spermatocytes.
The secondary spermatocytes after
maturation is known
as spermatids. Each Spermatids
goes on metamorphosis
into sperm by the process
of Spermatogenesis.
6. Structure of sperm: Structure of sperm has three part
1. Head 2.Middle piece 3.Tail
1. Head- It is flat and oval in human sperm. it is composed of
a large posterior nucleus and a small anterior acrosome.
Acrosome- acrosome is formed from the Golgi complex. It
contains digestive enzyme sperm lysin .it is the cap like
covering above the nucleus. it is surrounded by double
membrane. its membrane are together called galea- capitis.
acrosome play important role in penetration of ovum by
sperm. Remaining part of the head is nucleus. narrow space
between the nucleus and the acrosome is termed as
perfortorium. Nucleus of the sperm is very small. In it
nucleoplasm and nucleolus are absent. it contains only
chromatin. At the base of the nucleus in a pit like depression
proximal centriole is present. in between the head and the
middle piece a small neck is present. in this neck part a distal
centriole is located both the central are at right angle to each
other. proximal centriole first induce cleavage in a fertilized
egg. first spindle fiber forms from it. Distal centriole gives rise
to the axial filament of the sperm. it has (9+2) two microtubule
arrangement.
7. 2. Middle piece-
This is known as the energy- chamber of the sperm.
many mitochondria spirally surrounded the axonema.
this is called “Nebenkern sheath”. this part provides
energy to the sperm for locomotion.
In middle piece ,cytoplasm is found in the form of a
thin-sheet called Manchette. at the posterior and of
the middle piece of a ring centriole is found. its
function it not known.
3. Tail-
The longest and the fibrous part of the sperm is
termed its tail .sperm moves with the help of its tail.
Basal granule of the tail is distal centriole tail has 2
part.
1.main part- this part of broad. it contains cytoplasm
and its rounded by two solid fibers.
2.Endpeace- this part is narrow in its cytoplasm is
absent only axonema is present. in its solid fibers are
also absent in the sperm of the certain animals, tail is
absent.
8. Structure of spermatid Changes in the sperm
1. Nucleus
2. Golgi complex
3. Distal centriole
4. Mitochondria
5. Cytoplasm
Shrinks and elongated.
Changes to acrosome.
Forms axial filament of sperm tail.
Form mitochondrial spiral of sheath called
nebenkern.
Generally lost except a thin sheath called
manchette.
Changes in spermatid to form sperm during spermatogenesis
9. Control:
In human male, spermatogenesis starts only at the age of puberty due to increased secretion
of gonadotropin releasing hormone (GnRH) from the hypothalamus of brain. GnRH
stimulates adenohypophysis to secrete two gonadotropins: FSH and ICSH. ICSH stimulates
the Leydig’s cells of testis to secrete male sex hormones, called androgens, most important
of which is testosterone.
Testosterone stimulates the spermatogenesis especially spermatogenesis. FSH stimulates the
Sertoli cells of testis to secrete certain factors which helps in the process of spermatogenesis.
It is called physiological control.
Significance:
(a) Produces haploid sperms.
(b) Crossing over may occur during meiosis-I, so producing variations.
(c) Proves evolutionary relationship.
10. Oogenesis
It is the process of formation of ova or egg in ovary.
Ovary: it is the primary female reproductive organ.
Shape and size: greyish pink almond shaped.
structure, size is 2.5-3.5 cm long, 2 cm wide and 1
cm thick.
Location: in the abdominal cavity, one on either
side of vertebral column behind kidney.
Each ovary can be differentiated into 3 parts
1. Outer germinal epithelium
2. Tunica albuginea: it is middle layer of delicate
connective tissue.
3. Stroma: it is the inner mass of connective tissue.
It is further differentiated into 2 layer-outer cortex
and inner medulla. It is lined with germinal
epithelium which form ovarian follicle. Each ovary
is composed of about 400000 ovarian follicle.
Ovaries are inactive before puberty, but stroma
already contain immature follicle; Primordial
follicle. Primordial follicle mature in about 28 days,
rapture and release ova; process known
as ovulation.
The germinal epithelium of ovarian follicle give ova
germ cell called Oogonia.
12. Oogenesis occur in 3 phages
i) Multiplication: The initial
phase of Oogenesis starts
during fetal stage. The
primary germ cell, Oogonia
develop from stem cell by
mitosis cell division. In adult
ovaries, primordial follicle
contains a primary oocyte.
Primary oocyte is also known
as ova mother cell, which
eventually produce ova.
ii) Growth or maturation phase:
the Oogonia undergoes
maturation. It is a diploid cell.
Mature Oogonia is known as
primary oocytes, which undergoes
meiosis, however, meiosis stopped
at Prophase-I.
13. iii) Meiotic phase: Completion of
meiosis-I produces a secondary
oocyte and a polar body. The second
meiosis division Secondary Oocyte
occur with unequal distribution of
cytoplasm producing large egg and a
small second polar body. Eventually 1
egg and 3 polar bodies are produced.
Simultaneously, the first polar body
may divide into two polar bodies or
may not divide at all. Thus only one
functional ovum is formed and the two
or three polar bodies soon degenerate.
In vertebrates the first polar body is
formed after the primary oocyte is
released from ovary and has entered
into the oviduct. The second polar
body is formed only when the sperm
enters into ovum during fertilization.
