1. Prions are infectious protein particles that cause transmissible spongiform encephalopathies like mad cow disease in animals and Creutzfeldt-Jakob disease in humans.
2. Prions propagate by inducing normal proteins to misfold into an abnormal shape, forming fibrils that accumulate in the brain and cause neurodegeneration.
3. Prions are extremely difficult to destroy as they are resistant to heat, chemicals, radiation, and protease digestion due to their abnormal protein structure. Effective sterilization requires methods that fully denature the prion protein structure such as strong acids or high pressure steam autoclaving.
Biological contamination is the dread of every person working with cell culture. When cultures become infected with microorganisms, or cross-contaminated by foreign cells, these cultures usually must be destroyed. Since the sources of culture contamination are ubiquitous as well as difficult to identify and eliminate, no cell culture laboratory remains unaffected by this concern. With the continuing increase in the use of cell culture for biological research, vaccine production, and production of therapeutic proteins for personalized medicine and emerging regenerative medicine applications, culture contamination remains a highly important issue. Cell line cross-contamination can be a problem for scientists working with cultured cells. Studies suggest anywhere from 15–20% of the time, cells used in experiments have been misidentified or contaminated with another cell line. Problems with cell line cross-contamination have even been detected in lines from the NCI-60 panel, which are used routinely for drug-screening studies. Major cell line repositories, including the American Type Culture Collection (ATCC), the European Collection of Cell Cultures (ECACC) and the German Collection of Microorganisms and Cell Cultures (DSMZ), have received cell line submissions from researchers that were misidentified by them. Such contamination poses a problem for the quality of research produced using cell culture lines, and the major repositories are now authenticating all cell line submissions. ATCC uses short tandem repeat (STR) DNA fingerprinting to authenticate its cell lines.
Biological contamination is the dread of every person working with cell culture. When cultures become infected with microorganisms, or cross-contaminated by foreign cells, these cultures usually must be destroyed. Since the sources of culture contamination are ubiquitous as well as difficult to identify and eliminate, no cell culture laboratory remains unaffected by this concern. With the continuing increase in the use of cell culture for biological research, vaccine production, and production of therapeutic proteins for personalized medicine and emerging regenerative medicine applications, culture contamination remains a highly important issue. Cell line cross-contamination can be a problem for scientists working with cultured cells. Studies suggest anywhere from 15–20% of the time, cells used in experiments have been misidentified or contaminated with another cell line. Problems with cell line cross-contamination have even been detected in lines from the NCI-60 panel, which are used routinely for drug-screening studies. Major cell line repositories, including the American Type Culture Collection (ATCC), the European Collection of Cell Cultures (ECACC) and the German Collection of Microorganisms and Cell Cultures (DSMZ), have received cell line submissions from researchers that were misidentified by them. Such contamination poses a problem for the quality of research produced using cell culture lines, and the major repositories are now authenticating all cell line submissions. ATCC uses short tandem repeat (STR) DNA fingerprinting to authenticate its cell lines.
1. What is pathogen variability?
2. Significance of pathogen Variability
3. Stages of variation
4. Mechanism of Variability in fungi
5. Characterization of variability among plant pathogens
1. What is pathogen variability?
2. Significance of pathogen Variability
3. Stages of variation
4. Mechanism of Variability in fungi
5. Characterization of variability among plant pathogens
Viruses are obligate intracellular parasites which means they can only grow or reproduce inside a host cell.
The primary purpose of virus cultivation:
To isolate and identify viruses in clinical samples.
To do research on the viral structure, replication, genetics, and effects on the host cell.
To prepare viruses for vaccine production.
Isolation of the virus is always considered a gold standard for establishing the viral origin of the disease
topics covered
CULTIVATION OF VIRUSES
Animal inoculation
Embryonated eggs
CAM
Allantoic cavity
Amniotic cavity
Yolk sac
Tissue culture
Organ culture
Explant culture
Cell culture
Primary cell culture
diploid cell culture
Continues cell lines
Viruses are obligate intracellular parasites so they depend on host for their survival. They cannot be grown in non-living culture media or on agar plates alone, they must require living cells to support their replication.Cultivation of viruses can be discussed under following headings:
Animal Inoculation
Inoculation into embryonated egg
Cell Culture
A cell line is a product of immortal cells that are used for biological research.
Cells used for cell lines are immortal, that happens if a cell is cancerous.
The cells can perpetuate division indefinitely which is unlike regular cells which can only divide approximately 50 times.
Human cell lines
MCF-7 breast cancer
HL 60 Leukemia
HEK-293 Human embryonic kidney
HeLa Henrietta lacks
Primate cell lines
Vero African green monkey kidney epithelial cells
Cos-7 African green monkey kidney cells
And others such as CHO from hamster, sf9 & sf21 from insect cells.
viruses are intracellular obligate parasites. They are either DNA or RNA viruses. In order to grow in labs, tissue culture is used. Some general characteristics of viruses are discussed here.
Seminar of U.V. Spectroscopy by SAMIR PANDASAMIR PANDA
Spectroscopy is a branch of science dealing the study of interaction of electromagnetic radiation with matter.
Ultraviolet-visible spectroscopy refers to absorption spectroscopy or reflect spectroscopy in the UV-VIS spectral region.
Ultraviolet-visible spectroscopy is an analytical method that can measure the amount of light received by the analyte.
Professional air quality monitoring systems provide immediate, on-site data for analysis, compliance, and decision-making.
Monitor common gases, weather parameters, particulates.
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.
Earliest Galaxies in the JADES Origins Field: Luminosity Function and Cosmic ...Sérgio Sacani
We characterize the earliest galaxy population in the JADES Origins Field (JOF), the deepest
imaging field observed with JWST. We make use of the ancillary Hubble optical images (5 filters
spanning 0.4−0.9µm) and novel JWST images with 14 filters spanning 0.8−5µm, including 7 mediumband filters, and reaching total exposure times of up to 46 hours per filter. We combine all our data
at > 2.3µm to construct an ultradeep image, reaching as deep as ≈ 31.4 AB mag in the stack and
30.3-31.0 AB mag (5σ, r = 0.1” circular aperture) in individual filters. We measure photometric
redshifts and use robust selection criteria to identify a sample of eight galaxy candidates at redshifts
z = 11.5 − 15. These objects show compact half-light radii of R1/2 ∼ 50 − 200pc, stellar masses of
M⋆ ∼ 107−108M⊙, and star-formation rates of SFR ∼ 0.1−1 M⊙ yr−1
. Our search finds no candidates
at 15 < z < 20, placing upper limits at these redshifts. We develop a forward modeling approach to
infer the properties of the evolving luminosity function without binning in redshift or luminosity that
marginalizes over the photometric redshift uncertainty of our candidate galaxies and incorporates the
impact of non-detections. We find a z = 12 luminosity function in good agreement with prior results,
and that the luminosity function normalization and UV luminosity density decline by a factor of ∼ 2.5
from z = 12 to z = 14. We discuss the possible implications of our results in the context of theoretical
models for evolution of the dark matter halo mass function.
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.
Observation of Io’s Resurfacing via Plume Deposition Using Ground-based Adapt...Sérgio Sacani
Since volcanic activity was first discovered on Io from Voyager images in 1979, changes
on Io’s surface have been monitored from both spacecraft and ground-based telescopes.
Here, we present the highest spatial resolution images of Io ever obtained from a groundbased telescope. These images, acquired by the SHARK-VIS instrument on the Large
Binocular Telescope, show evidence of a major resurfacing event on Io’s trailing hemisphere. When compared to the most recent spacecraft images, the SHARK-VIS images
show that a plume deposit from a powerful eruption at Pillan Patera has covered part
of the long-lived Pele plume deposit. Although this type of resurfacing event may be common on Io, few have been detected due to the rarity of spacecraft visits and the previously low spatial resolution available from Earth-based telescopes. The SHARK-VIS instrument ushers in a new era of high resolution imaging of Io’s surface using adaptive
optics at visible wavelengths.
The ASGCT Annual Meeting was packed with exciting progress in the field advan...
virus culturing and prions
1. M. Talha Iftikhar
Roll no.15821
Topic: Virus Culturing and Prions
Submitted to: Prof Dr. Muhammad Ismail
Department of Bioinformatics and Biotechnology
Government College University, Faisalabad
2. Culturing of Viruses
Isolationof Viruses
Unlike bacteria, many of which can be grown on an artificial nutrient medium, viruses require a
living host cell for replication. Infected host cells (eukaryotic or prokaryotic) can be cultured and
grown, and then the growth medium can be harvested as a source of virus. Virions in the liquid
medium can be separated from the host cells by either centrifugation or filtration. Filters can
physically remove anything present in the solution that is larger than the virions; the viruses can
then be collected in the filtrate.
Membrane filters can be used to remove cells or viruses from a solution. (a) This scanning electron micrograph shows
rod-shaped bacterialcells captured on the surface of a membrane filter. Note differences in the comparative size of the
membrane pores and bacteria. Viruses will pass through this filter. (b) The size of the pores in the filter determines what
is captured on the surface of the filter (animal [red]and bacteria [blue]) and removed from liquid passing through.Note
the viruses (green) pass through the finer filter.
3. Cultivation of Viruses
By Bacteria Culture:
Viruses can be grown in vivo (within a whole living organism, plant, or animal) or in vitro
(outside a living organism in cells in an artificial environment, such as a test tube, cell culture
flask, or agar plate). Bacteriophages can be grown in the presence of a dense layer of bacteria
(also called a bacterial lawn) grown in a 0.7 % soft agar in a Petri dish or flat (horizontal) flask
(see Figure 2). The agar concentration is decreased from the 1.5% usually used in culturing
bacteria. The soft 0.7% agar allows the bacteriophages to easily diffuse through the medium.
For lytic bacteriophages, lysing of the bacterial hosts can then be readily observed when a clear
zone called a plaque is detected. As the phage kills the bacteria, many plaques are observed
among the cloudy bacterial lawn.
(a) Flasks like this may be used to culture human or animal cells for viral culturing. (b) These plates contain
bacteriophage T4 grown on an Escherichia coli lawn. Clear plaques are visible where host bacterial cells have been lysed.
Viral titers increase on the plates to the left.
In an Embryo:
Animal viruses require cells within a host animal or tissue-culture cells derived from an animal.
Animal virus cultivation is important for 1) identification and diagnosis of pathogenic viruses in
clinical specimens, 2) production of vaccines, and 3) basic research studies. In vivo host sources
can be a developing embryo in an embryonated bird’s egg (e.g., chicken) or a whole animal. For
example, most of the influenza vaccine manufactured for annual flu vaccination programs is
cultured in hens’ eggs.
The embryo or host animal serves as an incubator for viral replication. Location within the
embryo or host animal is important. Many viruses have a tissue tropism, and must therefore be
introduced into a specific site for growth. Within an embryo, target sites include the amniotic
cavity, the chorioallantoic membrane, or the yolk sac. Viral infection may damage tissue
4. membranes, producing lesions called pox; disrupt embryonic development; or cause the death
of the embryo.
(a) The cells within chicken eggs are used to culture different types of viruses. (b) Viruses can be replicated in various
locations within the egg, including the chorioallantoic membrane,the amniotic cavity, and the yolk sac.
In Animal Cells:
For in vitro studies, various types of cells can be used to support the growth of viruses. A
primary cell culture is freshly prepared from animal organs or tissues. Cells are extracted from
tissues by mechanical scraping or mincing to release cells or by an enzymatic method using
trypsin or collagenase to break up tissue and release single cells into suspension.
Because of anchorage-dependence requirements, primary cell cultures require a liquid culture
medium in a Petri dish or tissue-culture flask so cells have a solid surface such as glass or plastic
for attachment and growth. Primary cultures usually have a limited life span. When cells in a
primary culture undergo mitosis and a sufficient density of cells is produced, cells come in
contact with other cells. When this cell-to-cell-contact occurs, mitosis is triggered to stop. This
is called contact inhibition and it prevents the density of the cells from becoming too high. To
prevent contact inhibition, cells from the primary cell culture must be transferred to another
vessel with fresh growth medium. This is called a secondary cell culture. Periodically, cell
density must be reduced by pouring off some cells and adding fresh medium to provide space
and nutrients to maintain cell growth. In contrast to primary cell cultures, continuous cell lines,
usually derived from transformed cells or tumors, are often able to be subcultured many times
or even grown indefinitely (in which case they are called immortal). Continuous cell lines may
not exhibit anchorage dependency (they will grow in suspension) and may have lost their
contact inhibition. As a result, continuous cell lines can grow in piles or lumps resembling small
tumor growths.
5. Cells for culture are prepared by separating them from their tissue matrix. (a) Primary cell cultures grow attached to the
surface of the culture container. Contact inhibition slows the growth of the cells once they become too dense and begin
touching each other. At this point, growth can only be sustained by making a secondary culture. (b) Continuous cell
cultures are not affected by contact inhibition. They continue to grow regardless of cell density.
An example of an immortal cell line is the HeLa cell line, which was originally cultivated from
tumor cells obtained from Henrietta Lacks, a patient who died of cervical cancer in 1951. HeLa
cells were the first continuous tissue-culture cell line and were used to establish tissue culture
as an important technology for research in cell biology, virology, and medicine. Prior to the
discovery of HeLa cells, scientists were not able to establish tissue cultures with any reliability
or stability. More than six decades later, this cell line is still alive and being used for medical
research. See “The Immortal Cell Line of Henrietta Lacks” below to read more about this
important cell line and the controversial means by which it was obtained.
Prions
What they are?
Prions are infectious agents composed entirely of a protein material that can fold in multiple,
structurally abstract ways, at least one of which is transmissible to other prion proteins, leading
to disease in a manner that is epidemiologically comparable to the spread of viral infection.
6. Prions composed of the prion protein (PrP) are believed to be the cause of transmissible
spongiform encephalopathies (TSEs) among other diseases.
Prions were initially identified as the causative agent in animal bovine spongiform
encephalopathy (BSE)—known popularly as "mad cow disease".
Human prion diseases include Creutzfeldt–Jakob disease (CJD) and its variant (vCJD),
Gerstmann–Sträussler–Scheinker syndrome, fatal familial insomnia, and kuru. All known prion
diseases in mammals affect the structure of the brain or other neural tissue.
No effective medical treatment is known. The illness is progressive and always fatal.
How they propagate:
Prions may propagate by transmitting their misfolded protein state. When a prion enters a
healthy organism, it induces existing, properly folded proteins to convert into the misfolded
prion form. In this way, the prion acts as a template to guide the misfolding of more proteins
into prion form.
In yeast, this refolding is assisted by chaperone proteins such as Hsp104. These refolded prions
can then go on to convert more proteins themselves, leading to a chain reaction resulting in
large amounts of the prion form.
Structure:
Basic Structure Normal prions contain about 200-250 amino acids twisted into three telephone
chord-like coils known as helices, with tails of more amino acids
Basic Structure The mutated, and infectious, form is built from the same amino acids but take a
different shape.100 times smaller than the smallest known virus.
7.
8. All known prions induce the formation of an amyloid fold, in which the protein polymerises into
an aggregate consisting of tightly packed beta sheets. Amyloid aggregates are fibrils, growing at
their ends, and replicate when breakage causes two growing ends to become four growing
ends. The incubation period of prion diseases is determined by the exponential growth rate
associated with prion replication, which is a balance between the linear growth and the
breakage of aggregates The propagation of the prion depends on the presence of normally
folded protein in which the prion can induce misfolding; animals that do not express the normal
form of the prion protein can neither develop nor transmit the disease.
Prion aggregates are extremely stable and accumulate in infected tissue, causing tissue damage
and cell death. This structural stability means that prions are resistant to denaturation by
chemical and physical agents, making disposal and containment of these particles difficult.
Transmission:
Current research suggests that the primary method of infection in animals is through ingestion.
It is thought that prions may be deposited in the environment through the remains of dead
animals and via urine, saliva, and other body fluids. They may then linger in the soil by binding
to clay and other minerals.
Sterilization:
Infectious particles possessing nucleic acid are dependent upon it to direct their continued
replication. Prions, however, are infectious by their effect on normal versions of the protein.
Sterilizing prions, therefore, requires the denaturation of the protein to a state in which the
molecule is no longer able to induce the abnormal folding of normal proteins. In general, prions
are quite resistant to proteases, heat, ionizing radiation, and formaldehyde treatments
although their infectivity can be reduced by such treatments. Effective prion decontamination
relies upon protein hydrolysis or reduction or destruction of protein tertiary structure.
Examples include sodium hypochlorite, sodium hydroxide, and strongly acidic detergents such
as 134 °C (274 °F) for 18 minutes in a pressurized steam autoclave has been found to be
somewhat effective in deactivating the agent of disease. Ozone sterilization is currently being
studied as a potential method for prion denaturation and deactivation.