Telomere Indicator of Physiological Age

Published in Genetics
Saturday, 12 August 2017 13:06
Have you ever wondered, what is your physiological age? Is it more or less than your chronological age? Physiological age determines a person’s health condition. Are we able to determine physiological age? You would think the answer is NO. but it can be done by determining telomere’s length. “Telomere is a repetitive nucleotide sequence (having no meaningful information) at each end of chromosome to protect DNA from deterioration and or from fusion with other chromosomes.” This sequence is about 3000-15000 base pairs in length. In vertebrates this repeated sequence is TTAGGG.
 
Significance of Telomeres
 
Cells divide and increase their number, DNA duplication also occurs. Enzymes involved in this duplication process, can’t continue duplication all the way to the end so some part of DNA is lost and chromosome is shortened. This lost part is some base pairs of telomere. Somatic cells lose about 50-100 nucleotides on each cell division. In this way, telomeres, having no meaningful information, act as CAPS preventing the important information (DNA) from deterioration and preserve the critical information. Telomeres are never tied to each other which allows chromosomes to remain segregate. Without telomeres, chromosomes would fuse with each other. Telomere Shortening Telomeres shorten because of the two major factors:
 
  1. End replication problem in eukaryotes accounts for loss of 20 base pairs per cell division.
  2. Oxidative stress accounts for loss of 50-100 base pairs per cell division.
 
Figure 827.1
 
Oxidative stress in the body depends on lifestyle factors. Smoking, poor diet and stress can cause increase in oxidative stress. With each cell division telomeres shorten, so there are limited number of divisions that a cell can undergo, this limit is called Hayflick Limit. This is to prevent the loss of vital DNA information and to prevent production of abnormal cells. When a cell reaches this limit it undergoes apoptosis that is a programmed cell death. Telomere Lengthening to reverse telomere shortening, there is an enzyme named Telomerase that adds telomere sequence nucleotides and replenish the lost telomere nucleotides. Telomerase activity is not present in all cells. It is almost absent in somatic cells including; lung, liver, kidney cells, adult tissues, cardiac and skeletal muscles etc. In the presence of telomerase enzyme, a cell can divide to unlimited extent without ageing giving rise to tumors. That’s why it is found only in some cells in considerable concentration including germline cells and stem cells. These cells don’t show signs of ageing.
 
Figure 827.3
 
Relation between Telomere’s Shortening and Ageing
 
Figure 827.2It is still controversial that whether telomere shortening is a reason of ageing or is a sign of ageing just like grey hair. Whatever it is, the thing is, it determines your physiological age because ageing cells mean an ageing body. Telomere shortening is related with poor lifestyle. People who are active and have a healthy lifestyle have the same telomere length as someone 10 years younger than them has. Depression causes increase in oxidative stress in the body so the higher the stress, the shorter the telomere is Link between Telomeres and Cancer “Cancer in general is defined as an uncontrollable rapid growth of cells.”
 
What causes these cells to grow uncontrollably?
 
These cells have active telomerase enzyme, which doesn’t let the telomere to shorten, so no Hayflick limit reaches and cell continues to divide. This is the reason why telomerase is not used as an anti-ageing medicine because it has potential to turn normal body cells into cancerous cells. Without telomerase activity cancer cells activity would stop, which is an under research treatment for cancer. However, drugs inhibiting telomerase activity, can interfere with normal functioning of cells that require telomerase. In healthy female breast there is a portion of cells named, luminal progenitors, with critically short telomere length. In these cells telomerase becomes active causing these cells to turn into cancer cells on higher activity. To tackle breast cancer, use of telomerase inhibiting drugs should be practiced. Telomere biology is very important for understanding cancer biology and scientists are working hard on it.
 
 
Reviewed by Dr. Nida Hayat Khan
Editor @ BioScience.pk 

TERMINOLOGIES USED IN FLOWCYTOMETRY

Published in Hemotology
Saturday, 29 July 2017 15:09
Fluorescence
 
A fluorochrome absorbs light energy and emits excess energy in the form of photon light (fluorescence). Fluorescence is the property of molecules to absorb light at one wavelength and emit light at a longer wavelength. The fluorescent dyes commonly used in flow cytometry are fluorescein isothiocyanate (FITC) and phycoerythrin (PE). The fluorochrome-labeled antibodies are used for detection of antigenic markers on the surface of cells. A particular cell type can be identified on the basis of the antigenic profile expressed. Multiple fluorochromes can be used to identify different cell types in a mixed population of cells.
 
Light Scatter
 
Light is scattered when the incident light is deflected by a particle traversing through a beam of light. This depends on the physical properties of the cell. Two forms of light scatter are used to identify different cell types: forward scatter and side scatter. Forward scatter (light scattered in the same direction as the laser beam) is related to cell size. Side scatter (light scattered at a 90° angle to the laser beam) is related to internal granularity of the cell. Main subpopulations of leukocytes are identified on the basis of correlated measurements of forward and side scatters. When a cell passes through laser beam, side scatter and fluorescent signals that are emitted by the cell are directed to photomultiplier tubes, while the forward scatter signals are directed to a photodiode. Photomultiplier tubes and photodiodes are called as detectors. Optical filters are placed before the detectors that allow only a narrow range of wavelengths to reach the detectors (see Figure 806.1).
 
Figure 806.1 Principle of working of a flow cytometer
Figure 806.1 Principle of working of a flow cytometer
 
Data Analysis
 
The data collected and stored in the computer can be displayed in various formats. A parameter means forward scatter, or side scatter, or emitted fluorescence from a particle as it passes through a laser beam. A histogram is a data plot of a single parameter, with the parameter’s signal value in channel numbers or relative fluorescence intensity on X-axis (horizontal axis) and number of events on the Y-axis. A dot plot is a two parameter data graph in which each dot represents one event that the flow cytometer analyzed; one parameter is displayed on the X-axis and the other on the Y-axis. A 3-D plot represents one parameter on X-axis, another parameter on Y-axis, and number of events per channel on Z-axis.
 
Gating
 
A gate is a boundary that can be set to restrict the analysis to a specific population within the sample. For example, a gate boundary can be drawn on a dot plot or histogram to restrict the analysis only to cells with the size of lymphocytes. Gates can be inclusive (selection of events that fall within the boundary) or exclusive (selection of events that fall outside the boundary). Data selected by the gate is then displayed in subsequent plots.
 
Sorting
 
Usually, when a cell passes through the laser beam, it is sent to waste. Sorting consists of collecting cells of interest (defined through criteria of size and fluorescence) for further analysis (such as microscopy or functional or chemical analysis). Sorting feature is available only in some flow cytometers.

International Council for Standardization in Haematology (ICSH)

Published in Hemotology
Saturday, 22 July 2017 11:23
The International Council for Standardization in Haematology (ICSH) was initiated as a standardization committee by the European Society of Haematology (ESH) in 1963 and officially constituted by the International Society of Hematology (ISH) and the ESH in Stockholm in 1964. The ICSH is recognised as a Non-Governmental Organisation with official relations to the World Health Organisation (WHO).
 
The ICSH is a not-for-profit organisation that aims to achieve reliable and reproducible results in laboratory analysis in the field of diagnostic haematology.
 
The ICSH coordinates Working Groups of experts to examine laboratory methods and instruments for haematological analyses, to deliberate on issues of standardization and to stimulate and coordinate scientific work as necessary towards the development of international standardization materials and guidelines.

Prickly Heat Rash: Cause, Symptoms and Treatment

Published in Informative
Sunday, 02 July 2017 15:39
Prickly heat usually clears up on its own within a few days. However, in serious cases heat rash can interfere with the body's heat-regulating mechanism and cause heat exhaustion.
 
Heatstroke is a more serious condition when the body can no longer cool itself. This is a medical emergency.
 
What causes prickly heat rash?
 
Heat rash begins with excessive perspiration, usually in a hot, humid environment. The perspiration makes it easier for dead skin cells and bacteria on the skin to block the sweat glands, forming a barrier and trapping sweat beneath the skin, where it builds up, causing the characteristic bumps. As the bumps burst and sweat is released, there may be a prickly, or stinging sensation that gives this condition its name.

What are the symptoms of heat rash?
 
Small, itchy red bumps on the skin are the symptoms of heat rash. The rash may feel prickly, stinging or burning.
 
Seek medical advice if:
 
  • Heat rash does not go away on its own within a few days.
  • You develop an infection in an area where you recently had heat rash.
 
What are the treatments for heat rash?
 
In most cases, heat rash will clear up on its own in a few days if the affected area is kept cool and dry. Avoid excessive heat and humidity and cool off with a fan, take a cool shower or bath and let your skin air dry, or if you have air-conditioning, use this to cool yourself. Once the skin is cool and dry again, don’t use any type of oil-based product, which might block your sweat glands. Calamine lotion and/or hydrocortisone cream can relieve itching and irritation.
 
If your prickly heat does not go away within a few days, or if you develop an infection where the bumps have burst, you may need medication, so seek medical advice.

How can I prevent heat rash?
 
To prevent heat rash, avoid situations that can lead to excessive sweating, such as hot, humid environments and strenuous physical activity. In hot weather, use fans and cool showers and baths to stay cool, or air conditioning if available; dry your skin thoroughly; and wear lightweight, loose-fitting clothes ideally made from cotton.

IMPORTANT THEORIES AND LAWS PIONEERS AND PROPOSERS IN BIOLOGY

Published in Informative
Tuesday, 27 June 2017 00:27
  • Allen’s LawAllen
  • Artificial ParthenogenesisLoeb
  • Axial Gradient theoryChild
  • Bergman’s RuleBergman
  • Biogenetic LawEarnst Haeckel (1868)
  • Biological Species ConceptEarnst Mayer
  • Biogenesis TheoryDeveloped by F. Redi
  • Chromosomal Theory of InheritanceSutton and Boveri
  • Theory of natural selectionCharles Darwin

DISCOVERERS AND INVENTORS IN BIOLOGY

Published in Informative
Monday, 26 June 2017 23:39

Amino acid sequence of protein (insulin)
Sanger

Anaerobic release of energy
L-Pasteur (1878)

Bacteria
Leeuwenhoek

Pure culture of Bacteria
Lister J.

Bacteriophage
Towrt and De Herelle (1915)

Blood Capillaries
Marcello Malpighi

Blood Groups
Karl Landsteiner

Blood Circulation
William Harvey

Bioluminescence
E.R. Dubois

Biocatalysts
Buchner

Cyanophage
Saffermann and Morris

First description of cell (RBC)
Jan Swammerdam (1658)

Cell
Robert Hooke (1665)

Living cell
A.V. Leeuwenhoek

Cell Theory
Schleiden and Schwann

Centrosome
Van Benden

Centriole
Van Benden

Chromosomes
Hofmeister

Golgi bodies
Cammileo Golgi

Plastids
Haeckel (1866)

Chioroplast
Schimper

Mitochondria
Kolliker (1880)

Microtubules
Robertis and Francis

Microfilaments
Paleviz et. al (1975)

Nucleus
Robert Brown

Nucleolus
Fontana

Nucleoplasm
Strasburger

Ribosomes (Animal cell)
Palade

Sphaerosome
Pernes (1953)

Astral rays and spindle
Beevers

Endoplasmic reticulum
Porter

Central Dogma
F.H.C. Crick (1918)

Coenzyme A
C. Lipmann

Chlorophyll structure
Willstartter and Fisher

Cyclosis
Amid

Cytochrome
C.A. Macmunn (1886)

Citric Acid cycle
Hans A. Krebs

Double Helical Structure of DNA
Watson and Crick

Biological Synthesis of DNA with template
A. Kornberg.

biological synthesis of DNA without template
H.G. Khorona

Enzyme
Buchner

Embryo culture
Laiback

Extra embryonic membranes
Von Baer

Fertilization in plants
E. Strasburger

Double fertilization
Nawaschin

Go phase
Lajtha

Gaseous exchange in blood
Ludwig (1872)

Genetic defects in human
Sir Archibald Garrod

Giant Salivary gland chromosomes
Balbiani (1881)

Hormones
Beylis and Starling

Heterothallism
Blackslee

Interferon
Issacs and Linderman

Insulin use for treatment of diabetics
Banting

Mendelism
G. Mendel

Rediscoverer of Mendelism
Correns, Hugo de Vries and Tschmark

Microtome
W. His

Micro-organisms
Leeuwenhoek

Mitosis
W. Flemming

Meiosis
Farmer and Moore

Mutations
Hugo de Vries

Nucleic acid
Meishcher called it ‘Nuclein’

Ovum (Mammalian)
Karl E. Von Baer

Omnis cellula e cellula
R. Virchow

Pinocytosis
Edward and Lewis

Phagocytosis
Metchnikoff

Penicillin
Alexander Flemming

Plasmodesmata
Strasburger

Photorespiration
Garner and Allard

Quantosome
Park and Bigginis (1960)

Quiescent centre
Clowes

Protoplasm Physical basis of life
Huxley

Streptomycin
Salmon Waksman

Techniques Chromatograph
M. Tswett

Tissue culture
A. Carrel

Isotopic tracing
G. Havesy

Measuring gaseous exchange manometry
O. Warburg

Locating DNA in cell
A. Feulgen

Ultracentrifugation
T. Svedberg

Avena curvature test
Went

Teminism (Reverse Transcription)
Temin

Synthesis of urea
Wohler

Virus
D. Iwanovsky

Obtained crystals of virus
Stanley

WORLD DAYS WITH INTERNATIONAL IMPORTANCE

Published in Informative
Sunday, 25 June 2017 22:05

Antileprosy day
30th Jan

International Women day
8th March

World Handicaps day
15th March

World Forest day
21st March

World Tuberculosis day
26th March

World Health day
7th April

World Earth day
22nd April

International Sun day (Non-conventional Energy sources day)
3rd May

World Red Cross day
8th May

World No Tobacco Day
31st May

World Environment day
5th June

World Population Day
11th July

Hiroshima and Nagasaki Day
6th Aug

Malaria day (mosquito day)
20th Aug

Blood Donation Day
1st Oct

World Animal Day
3rd Oct

World habitat Day
4th Oct

World Food Day
16th Oct

World Diabetes Day
14 Nov

World AIDS Day
1st Dec

National Pollution Prevention Day
2nd Dec

World conservation Day
3rd Dec

International Day for Biological Diversity
29th Dec

RESEARCH INSTITUTES IN PAKISTAN

Published in Informative
Saturday, 24 June 2017 00:25
  • Abdul Qadir Khan Research Laboratories
  • Energy Conservation Cell (ENERCON), Islamabad
  • Drainage Research Institute of Pakistan (DRIP), Hyderabad
  • Forestry Institute, Peshawar
  • Ghulam Ishaq Khan Institute of Advanced Science and Technology, Tarbella
  • Geological Survey of Pakistan, Rawalpindi
  • Irrigation, Drainage, and Flood Control Research Council, Islamabad
  • National Center for Technology Transfer (NCTT), Islamabad
  • National Institute of Health (NIH), Islamabad
  • Nuclear Institute of Agricultural Biology (NIAB), Faisalabad
  • Pakistan Agricultural Research Council (PARC), Islamabad
  • Pakistan Arts Council
  • Pakistan Atomic Energy Commission (PAEC), Islamabad
  • Pakistan Council of Industrial and Scientific Research (PCSIR)
  • Pakistan Science Foundation (PSF), Islamabad
  • Pakistan Health Research Council (PHRC), Islamabad
  • Silicon Institute of Technology, Islamabad
  • Space and Upper Atmosphere Research Council (SUPPARCO), Karachi

H. Gobind Khorana - Biographical

Published in Informative
Sunday, 12 March 2017 18:08

Har Gobind Khorana was born of Hindu parents in Raipur, a little village in Punjab, which is now part of eastern Pakistan. The correct date of his birth is not known; that shown in documents is January 9th, 1922. He is the youngest of a family of one daughter and four sons. His father was a «patwari», a village agricultural taxation clerk in the British Indian system of government. Although poor, his father was dedicated to educating his children and they were practically the only literate family in the village inhabited by about 100 people.

Har Gobind Khorana attended D.A.V. High School in Multan (now West Punjab); Ratan Lal, one of his teachers, influenced him greatly during that period. Later, he studied at the Punjab University in Lahore where he obtained an M. Sc. degree. Mahan Singh, a great teacher and accurate experimentalist, was his supervisor.

Khorana lived in India until 1945, when the award of a Government of India Fellowship made it possible for him to go to England and he studied for a Ph. D. degree at the University of Liverpool. Roger J. S. Beer supervised his research, and, in addition, looked after him diligently. It was the introduction of Khorana to Western civilization and culture.

Khorana spent a postdoctoral year (1948-1949) at the Eidgenössische Technische Hochschule in Zurich with Professor Vladimir Prelog. The association with Professor Prelog molded immeasurably his thought and philosophy towards science, work, and effort.

After a brief period in India in the fall of 1949, Khorana returned to England where he obtained a fellowship to work with Dr. (now Professor) G. W. Kenner and Professor (now Lord) A. R. Todd. He stayed in Cambridge from 1950 till 1952. Again, this stay proved to be of decisive value to Khorana. Interest in both proteins and nucleic acids took root at that time.

A job offer in 1952 from Dr. Gordon M. Shrum of British Columbia (now Chancellor of Simon Fraser University, British Columbia) took him to Vancouver. The British Columbia Research Council offered at that time very little by way of facilities, but there was «all the freedom in the world», to use Dr. Shrum's words, to do what the researcher liked to do. During the following years, with Dr. Shrum's inspiration and encouragement and frequent help and scientific counsel from Dr. Jack Campbell (now Head of the Department of Microbiology at the University of British Columbia), a group began to work in the field of biologically interesting phosphate esters and nucleic acids. Among the many devoted and loyal colleagues of this period, there should, in particular, be mention of Dr. Gordon M. Tener (now a Professor in the Biochemistry Department of the University of British Columbia), who contributed much to the spiritual and intellectual well-being of the group.

In 1960 Khorana moved to the Institute for Enzyme Research at the University of Wisconsin. He became a naturalized citizen of the United States. As of the fall of 1970 Khorana has been Alfred P. Sloan Professor of Biology and Chemistry at the Massachusetts Institute of Technology.

Har Gobind Khorana was married in 1952 to Esther Elizabeth Sibler, who is of Swiss origin. Esther brought a consistent sense of purpose into his life at a time when, after six years' absence from the country of his birth, Khorana felt out of place everywhere and at home nowhere. They have three children: Julia Elizabeth (born May 4th, 1953), Emily Anne (born October 18th, 1954), and Dave Roy (born July 26th, 1958).

Towards a cure for herpesviruses: Targeting infection with CRISPR/Cas9

Published in Informative
Tuesday, 22 November 2016 13:35

Most adults carry multiple herpesviruses. Following the initial acute infection, these viruses establish life-long infections in their hosts and cause cold sores, keratitis, genital herpes, shingles, infectious mononucleosis, and other diseases. Some herpesviruses can cause cancer in man. During the latent phase of infection, the viruses remain dormant for long periods of time, but retain the capacity to cause occasional reactivations, that may lead to disease. A study published on June 30th in PLOS Pathogens suggests that attacking herpesvirus DNA with CRISPR/Cas9 genome editing technology can suppress virus replication and, in some cases, lead to elimination of the virus.

The CRISPR/Cas9 system targets specific DNA sequences and induces clean cuts across both strands of the DNA. In mammalian cells, such cuts are flagged and quickly repaired by an emergency repair system called NHEJ (for non-homologous end-joining). NHEJ is efficient but not very accurate and often results in insertion or deletion of a few DNA bases at the repair site. Because DNA is read in codons of three bases at a time, such small changes in critical positions often destroy the function of the respective gene and its protein product.

Robert Jan Lebbink, from the University Medical Center in Utrecht, The Netherlands, and colleagues reasoned that CRISPR/Cas9 could target and mutate latent herpesvirus DNA in infected human cells and so potentially prevent herpesvirus-associated diseases. To test this, the researchers devised specific guide (g)RNAs—sequences that are complementary to vital parts of the viral genome and function as 'molecular addresses'. These gRNAs, combined with the 'molecular scissors' part of the CRISPR/Cas9 system, should induce specific cuts and subsequent mutations in the herpesvirus DNA, and so cripple the viruses.

In their systematic approach, the researchers looked at three different members of the herpesvirus group: herpes simplex virus type 1 (HSV-1) causing cold sores and herpes keratitis; human cytomegalovirus (HCMV), the most common viral cause of birth defects (when the virus is transmitted from mother to fetus); and Epstein-Barr virus (EBV) causing infectious mononucleosis and multiple types of cancer.

Working with lymphoma cells latently infected with EBV, the researchers showed that introduction of gRNAs that target specific EBV DNA sequences can introduce mutations at the targeted sites. Such mutations can eliminate essential functions of the virus as well as de-stabilize the viral DNA molecules. Consistent with this, the researchers report that by using two different gRNAs targeting an essential EBV gene, they can induce loss of over 95% of EBV genomes from the host cells.

During latent infection, HCMV genomes exist as circular DNA molecules in the nucleus of host cells. Upon virus reactivation, HCMV replication proceeds slowly. With appropriate gRNAs, the researchers found that CRISPR/Cas9 editing can efficiently impair HCMV replication. However, they also observed emergence of escape variants that bypass CRISPR/Cas9 editing, suggesting that simultaneous editing at multiple critical sites in the HCMV genome is necessary to avoid the development of resistant genomes.

Compared to HCMV, HSV-1 multiplies much faster. When the researchers tested various gRNAs targeting different essential HSV-1 genes in conjunction with CRISPR/Cas9, they found that many of them were able to reduce virus replication. When they combined two of those gRNAs, thereby simultaneously targeting two essential genes, they were able to completely suppress HSV-1 replication. On the other hand, they were unable to induce editing during the latent phase, i.e. when the viral DNA was not actively multiplying.

"We observed highly efficient and specific clearance of EBV from latently infected tumor cells and impairment of HSV-1 and HCMV replication in human cells", the researchers summarize. They go on to say, "although CRISPR/Cas9 was inefficient at directing genome engineering of quiescent HSV-1, virus replication upon reactivation of quiescent HSV-1 was efficiently abrogated using anti-HSV-1 gRNAs". Their results, they hope, "may allow the design of effective therapeutic strategies to target human herpesviruses during both latent and productive infections."

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