Author: Nitin Bayal
National Centre for Cell Science, Pune
My presumptions about leprosy were incorrect! Books and documentaries have spoken plenty in silence but still incomplete.
In the middle ages, it was one of the most feared diseases and was once considered as “Living Death”. There was a time when prevailing religious concepts kept our attention away from finding the root cause of leprosy transmission and religious institutions influenced the health and disease affairs. Illness due to leprosy was accepted as a curse from God or bad luck, just as many different phenomena that were not linked to cause-and-effect theory credited to the act of god, forcing people to plead and compensate for this unexplained experience.
Although after new advances in science and technology came into existence, it became difficult to arguably justify scientific reasoning with superstitions. The dreadful infections in leprosy have much more to say than eradication objectives. Prior to perusing a Ph.D. at National Centre for Cell Science, Pune; I knew very little about leprosy and Mycobacterium leprae, the causative organism of leprosy. Leprosy which causes poor wound healing, nerve damage and if left untreated it results in permanent disfigurement or loss of body parts, has for long been associated with a social stigma.
In India, for ages, ayurvedic preparations known as chaulmoogra oil was used to treat leprosy, and with the introduction of western medicine prescription drugs like Dapsone and Rifampicin, the catalog of every possible physical and chemical agent to indiscriminately kill the bad microbes is ever-expanding.
It is known to us that a leprosy patient loses the ability to feel the temperature change and pain in the affected area on their body; with the current understanding on the subject, we discovered some mysterious insights on leprosy research that encouraged skin microbiome research in leprosy. We added a brief note on each idea discussed in our research group. I tried to understand the diseased states, current therapeutics, and the problems that challenge scientists in this field.
M. leprae slowly gets resistant to new drugs and hence, raises concerns for a more severe form of the disease. In 1982, World Health Organization (WHO) released Multi-Drug Therapy (MDT) guidelines that dictate the planning and execution to eradicate leprosy. There is also the addition of newer drugs into the arsenal along with MDT treatment. Recently, scientists and clinicians speculated India accounts for 66% of leprosy patients worldwide. To challenge leprosy, WHO accelerated a global leprosy strategy for 2016-2020. A team of scientists led by Dr. GP. Talwar at All India Institute of Medical Science (AIIMS); New Delhi developed a vaccine in the 1970s that is finally recommended to launch on 2nd October 2019 after 36 years of testing in the clinical trials. As of now, it is well recognized that leprosy elimination has never been achieved actually in India.
Moreover, the frequency of resistant mutants also varies to different drugs, MDT treatment also kills the bacteria that are naturally resistant to drugs on the affected sites. It also affects the normal skin bacterial community.
Skin is the primarily affected organ in leprosy. This is where the skin microbiome plays its role to support normal homeostasis. The microbiome consists of an ecosystem of billions or trillions of microorganisms living in and on our bodies including skin. There is growing evidence that skin infections and drug abuse change or disturbs the skin microbiota in various types of skin pathological conditions like acne, eczema, psoriasis, skin allergies, and wounds.
We knew that both research scientists and clinicians play a critical role in the successful completion of studies on human subjects through mutual collaborations. While communicating with scientists, dermatologists, and workers of all levels at different NGOs, we finally found our collaborations in 2015 with leprosy clinics at LEPRA and TLM organizations for clinical samples. Then it was followed by regular meetings with patients and leprologists at leprosarium, where patients are kept for their treatment. The situation of patients was horrible because of their constant suffering, thus to understand the relationship between the skin microbiome and M leprae infection, researchers at DBT-National Centre for Cell Science and Bio-Sciences R&D, TCS Innovation Labs, Pune also collaborated to conduct a new study on the skin microbial communities from lesional and non-lesional skin of Indian leprosy patients undergoing multi-drug regimen treatment and healthy individuals covering two different geographical locations viz. Hyderabad and Miraj in India.
We obtained ethical and biosafety clearances and collaborated with Dr. Vijayalakshmi Valluri at LEPRA, Hyderabad and, Dr. Rohini Suryavanshi at TLM, Miraj, Maharashtra for clinical samples. We collected skin samples and extracted microbial DNA. We have used DNA sequencing methodologies and analysis tools to define the cutaneous microbiota. Our study has shown that the skin microbiota of healthy persons and leprosy patients have significant differences in its variety and abundance. The reasons also include the role of various external and internal factors comprising skin pH, skin thickness, skin moisture, hygiene, climate, etc. The photograph shown above was taken with consent at Richardson leprosy hospital, Miraj, Maharashtra, and pixelated to maintain the confidentiality of the leprosy patient.
Together with Dr. Milind S. Patole as doctoral co-supervisor, Dr. Dhiraj Paul, and Mr. Sunil Nagpal, one of my colleagues at TCS Innovation Labs, we have completed computational analysis on high-throughput sequencing data. We have published the first report on the structure of skin microbiota from India in Springer Nature journals i.e., Nature Scientific Data and Nature Scientific Reports journals. The corresponding authors, Dr. Shekhar C. Mande is Secretary DSIR and Director General, CSIR, New Delhi and Dr. Sharmila S. Mande is Chief Scientist and Head of Bio-Sciences R&D, TCS Research, Pune. They are leading scientists and specialized in Structural Biology and Microbiome research respectively.
Our analysis shows differences in the microbiota of affected and unaffected sites on the skin of leprosy patients and similarities among healthy persons irrespective of our sampling sites in India. Microbial diversity probes a distinct depletion of Staphylococcus genera in samples from affected sites of leprosy patients. Major abundant bacteria observed were Pseudomonas, Staphylococcus, Paracoccus, Brevundimonas, Limnobacter, Methylobacterium, Propionibacterium, Corynebacterium, Kocuria, and Streptococcus on the leprosy patient’s skin. It also shows a significant decline in firmicutes-related bacteria in leprosy patients in comparison to healthy individuals. It was a strange coincidence when M leprae attacks and occupy spaces in human bodies by either high exposure to infections or low immunity or both situations. M leprae is very intelligent, being a metabolically challenged bacterium it has managed to survive harsh conditions and still a mystery for the researchers for its cultivation in laboratory conditions. We are also afraid of liberal use of antibiotics and antiseptics that not only results in the extinction of some good bacteria but also kept the fortunate ones under constant threat.
The aspect of working with microbiome research can help skin microbiome transplantation science that corresponds to better disease management and diagnosis. A healthy microbiome protects humans from harmful settlers and infections by pathogens or opportunistic microorganisms.
Nowadays, many ventures are introducing probiotic products in the skin healthcare system and focusing on implications of skin’s health and appearance. The future of treating skin diseases is hopeful from microbiome research. However, despite these positive developments, measures to improve the healthcare system are also required. Humans often err in their haste. After all the great riches of leprosy are its paradoxes. If we are losing this time that will be another paradox, our luck may also prove contrary.
Author Bio: Nitin is a microbiome researcher at DBT-National Institute of Immunology, New Delhi. His interest mainly focus on data analytics in healthcare sector. He is an acclaimed scientific illustrator with a well disposed eye for art in daily lives. Nitin holds a degree of Master of Science in Molecular and Human Genetics and published his Ph.D work on leprosy research. His work is guided by a need to rationalize, make things beautiful, combine science with art and connect ideas.
Area of research: Skin biology, microbiome, sequencing technologies
Google Scholar link: https://scholar.google.com/citations?user=79o59fkAAAAJ&hl=en
Twitter handle: @BayalNitin
Recent findings by researchers at Yale points towards a host of genetic risk factors that explains susceptibility to the debilitating symptoms of post-traumatic stress disorder (PTSD) in veterans.
The Yale-led study published on Sept. 30 in the journal Biological Psychiatry has now identified a social factor that can mitigate these genetic risks: the ability to form loving and trusting relationships with others.
The study is one of the first to explore the role of nurture as well as nature in its investigation of the biological basis of PTSD.
“We exist in a context. We are more than our genes,” said Yale’s Robert H. Pietrzak, associate professor of psychiatry and public health, and senior author of the study.
Pietrzak is also director of the Translational Psychiatric Epidemiology Laboratory of the U.S. Department of Veterans Affairs National Center for PTSD.
Like many genetic studies on mental disorders such as depression, anxiety, and schizophrenia, PTSD studies have revealed numerous genetic risk factors that contribute to the severity of the disorder. For instance, a previous study of more than 165,000 U.S. military veterans led by Yale’s Joel Gelernter, the Foundations Fund Professor of Psychiatry and professor of genetics and of neuroscience, found variants in eight separate regions of the genome that help predict who is most likely to experience the repeated disturbing memories and flashbacks that are hallmark symptoms of PTSD.
In the new study, Pietrzak, Gelernter, and colleagues looked at psychological as well as genetic data collected from the National Health and Resilience in Veterans Study, a national sample of U.S. military veterans supported by the National Center for PTSD. The researchers specifically focused on a measure of attachment style — the ability or inability to form meaningful relations with others — as a potential moderator of genetic risk for PTSD symptoms.
Individuals with a secure attachment style perceive relationships as stable, feel that they are worthy of love and trust, and are able to solicit help from others. Those with an insecure attachment style report an aversion to or anxiety about intimacy with others, and have difficulty asking for help from others.
They found that the ability to form secure attachments essentially neutralized the collective effects of genetic risk for PTSD symptoms. The impact was particularly pronounced in a variant of the IGSF11 gene, which has been linked to synaptic plasticity or the ability of the brain to form new connections between brain cells.
Pietrzak noted that deficits in synaptic plasticity have also been linked to PTSD, depression, and anxiety, among other mental disorders. The findings illustrate the importance of integrating environmental and social as well as genetic factors in the study of PTSD and other mental disorders, the authors said.
“Social environmental factors are critical to informing risk for PTSD and should be considered as potential moderators of genetic effects,” he said. “The ability to form secure attachments is one of the strongest protective factors for PTSD and related disorders.”
The attachment styles may moderate polygenic risk for PTSD symptoms, along with the effects of a novel locus implicated in synaptic transmission and plasticity which may serve as a possible biological mediator of this association.
These findings may help inform interpersonally-oriented treatments for PTSD for individuals with high polygenic risk for this disorder and will help predict who is at greater risk of experiencing severe symptoms of PTSD, the study also suggest that psychological treatments targeting interpersonal relationships may help mitigate PTSD symptoms in veterans with elevated genetic risk for this disorder .
Amanda Tamman, formerly of Yale and now a Ph.D. student in clinical psychology at St. John’s University, is first author of the paper.
Yale News bulletin written by By Bill Hathaway. Article modified for style and clarity, Image source: Wikimedia Commons
Amanda J.F. Tamman, Frank R. Wendt, Gita A. Pathak, John H. Krystal, Janitza L. Montalvo-Ortiz, Steven M. Southwick, Lauren M. Sippel, Joel Gelernter, Renato Polimanti, Robert H. Pietrzak. Attachment style moderates polygenic risk for posttraumatic stress in United States military veterans: Results from the National Health and Resilience in Veterans Study. Biological Psychiatry, 2020; DOI: 10.1016/j.biopsych.2020.09.018
Pain is one of those feelings which if not all, most of us would never like to encounter and forget our previous encounters as well. However pain has been a necessary evil as it enables our bodies to recognize the occurrence of injuries or other problems which may not be always visible to our eyes, thus preventing further damage.
The International Association for the Study of Pain's widely used definition defines pain as "an unpleasant sensory and emotional experience associated with actual or potential tissue damage, or described in terms of such damage".
Before discovery of neurons responsible for pain by Charles Scott Sherrington in 1906 and the role of nociceptors, various theories were proposed to explain the origin of pain. Ancient Greeks including Hippocrates believed that it was due to an imbalance in vital fluids.
Now a team of researchers from Karolinska Institutet have now discovered a new sensory receptor organ in the skin that is sensitive to hazardous environmental irritation.
Conventionally pain has been thought to be initiated by activation of free nerve endings without end organs in the skin. In contrast to this paradigm, Abdo et al. discovered a previously unknown meshlike organ covering the skin that senses dangerous environmental stimuli. This organ is built from specialized glial cells with multiple long protrusions and which collectively go to make up a mesh-like organ within the epidermal-dermal border of skin. This organ is sensitive to painful mechanical damage such as pricks and pressure.
The present study describes what the new pain-sensitive organ looks like, how it is organised together with pain-sensitive nerves in the skin and how activation of the organ results in electrical impulses in the nervous system that result in reflex reactions and an experience of pain. In their experiments, the researchers also blocked the organ and saw a resultant decreased ability to feel mechanical pain.
"Our study shows that sensitivity to pain does not occur only in the skin's nerve fibres, but also in this recently-discovered pain-sensitive organ. The discovery changes our understanding of the cellular mechanisms of physical sensation and it may be of significance in the understanding of chronic pain," says Prof. Patrik Ernfors, professor at Karolinska Institutet's Department of Medical Biochemistry and Biophysics and chief investigator for the study.
The research was carried out with financial assistance from ERC, the Swedish Research Council, the Knut and Alice Wallenberg Foundation and Welcome Trust.
1. Abdo H, Calvo-Enrique L, Martinez Lopez J, Song J, Zhang MD, Usoskin D, El Manira A, Adameyko I, Hjerling-Leffler J, Ernfors P. Specialized cutaneous Schwann cells initiate pain sensation. Science, 2019 DOI: 10.1126/science.aax6452
2. Image source: Karolinska Instituet
3. Source article: Karolinska Instituet
This post is written specially keeping it consistent to the C.B.S.E curriculum for class XII. Nevertheless students from other boards can benefit from it too :)
Sexual reproduction in flowering plants (angiosperms) are carried out with the help of sexual organelles of the plant, i.e Flowers.Angiosperms: Angiosperms (Gr. Angios: Covered, Spermae: seed) are plants that have their seeds enclosed in a ovule inside the ovary of their flowers.
There is a huge diversity among flowers of the angiosperms but all flowers have these structures:
The ovary, which may contain one or multiple ovules, may be placed above other flower parts (referred to as superior); or it may be placed below the other flower parts (referred to as inferior).
Structure of Stamen, Anther, Pollen Sac/Microsporangium and Pollen Grain in Plants!
(a) The Stamen:
Stamen in a flower consists of two parts, the long narrow stalk like filament and upper broader knob-like bi-lobed anther (Fig. 2 A). The proximal end of the filament is attached to the thalamus or petal of the flower. The number and length of stamens vary in different species.
b) Structure of anther:
A typical angiosperm anther is bilobed with each lobe having two theca, i.e they are bithecous or dithecous anther is made up of two anther lobes, which are connected by a strip of sterile part called connective. The anther is a four-sided (tetragonal) structure consisting of four elongated cavities or pollen sacs (microsporangia) the four microsporangia are located at the corners, two in each lobe. The microsporangia develop further and become pollen sacs in which pollen grains are produced.(c) Structure of microsporangium
In a transverse section, a typical microsporangium appears circular in outline, consisting of two parts, microsporangial wall and sporogenous tissue.
i) Microsporangial Wall: Includes the epidermis, endothecium, middle layers and the tapetum. The outer three wall layers perform the function of protection and help in dehiscence of anther to release the pollen. The innermost wall layer is the tapetum, its cells have dense cytoplasm, become large, multinucleate and are specialized in nourishing the developing pollen grains.
Functions of Tapetum
It fills the interior of the microsporangium, all the cells are simmilar and called sporogenous cells. Sporogenous cells devide regularly to from the diploid microspore mother cells. The microspore mother cell devides to form pollen grains.
M icrosporogenesis : As the anther develops, the cells of the sporogenous tissue is capable of giving rise to a microspore tetrad. Each one is a potential pollen or microspore mother cell. The process of formation of microspores from a pollen mother cell (PMC) through meiosis is called microsporogenesis. The microspores, as they are formed, are arranged in a cluster of four cells–the microspore tetradmeiotic divisions to form microspore tetrads.
Types of microspore tetrads
As the anthers mature and dehydrate, the wall of the microspore mother cell degenerates and the microspores dissociate from each other and develop into pollen grains. Inside each microsporangium several thousands of microspores or pollen grains are formed that are released with the dehiscence of anther.
Pollen grains are male reproductive propagule or young male gametophyte which is formed in the anther and is meant for reaching the female reproductive organ through a pollinating agent. Pollen grains are generally spherical measuring about 25-50 micrometers in diameter. The pollen grains are coverd by a two-layered wall called sporoderm. The two layers of sporoderm are inner intine and outer exine.
1. Intine: It is the inner wall of the pollen grain and is a thin and continuous layer made up of cellulose and pectin. Some enzymatic proteins also occour in the intine.
2. Exine: The exine is the hard outer layer made up of sporopollenin which is one of the most resistant organic material known. It can withstand high temperatures and strong acids and alkali. No enzyme that degrades sporopollenin is so far known. Pollen grains where sporopollenin is absent can be easily identified by the presence of prominent apertures called germ pores. The exine surface may be smooth, pitted, reticulate, spiny, warty etc, the exine surface sculpting are specific for each type of pollen grain. Pollen grains are also well preserved as fossils because of the presence of sporopollenin, and thus are helpful in studying the evolutionary history of the plant.
The cytoplasm of a mature pollen grain is surrounded by a plasma membrane and contains two cells, the vegetative cell and generative cell. The vegetative cell is bigger, has abundant food reserve and a large irregularly shaped nucleus. The generative cell is small and floats in the cytoplasm of the vegetative cell. It is spindle shaped with dense cytoplasm and a nucleus. In over 60 per cent of angiosperms, pollen grains of a microsporeare shed at this 2-celled stage. In the remaining species, the pollen grain generative cell divides mitotically to give rise to the two male gametes before pollen grains are shed (3-celled stage).
Pollen grains of many species cause severe allergies and bronchial afflictions in some people often leading to chronic respiratory disorders – asthma, bronchitis, etc. However they are rich in neutrients and thus often consumed as food suppliment.
The Pistil, Megasporangium (ovule) and Embryo sac
The female reproductive parts of the flower are knwon as carpels, and are collectively called as gynoecium. Gynoecium may consist of a single pistil (monocarpellary) or may have more than one pistil (multicarpellary). When there are more than one carpel the pistils may be fused together (syncarpous) or may be free (apocarpous).
Each pistil has three parts, the stigma, style and ovary. The stigma serves as a landing platform for pollen grains. The style is the elongated slender part beneath the stigma. The basal bulged part of the pistil is the ovary. Inside the ovary is the ovarian cavity (locule). The placenta is located inside the ovarian cavity.
Structure of a Megasporangium (Ovule)
The ovule is a small structure attached to the placenta by means of a stalk called funicle. The body of the ovule fuses with funicle in the region called hilum. Thus, hilum represents the junction between ovule and funicle. Each ovule has one or two protective envelopes called integuments. Integuments encircle the nucellus except at the tip where a small opening called the micropyle is organised. Opposite the micropylar end, is the chalaza, representing the basal part of the ovule. The main body of the ovule is composed of parenchymatous mass called nucellus. Cells of the nucellus has abundant reserve of food. Located in the nucellus is the embryo sac or female gametophyte. An ovule generally has a single embryo sac formed from a megaspore.
It is the process of formation of haploid megaspore from the diploid megaspore mother cell (MMC). Usually a single MMC differentiates in the micropylar region. It is a large cell containing dense cytoplasm and a prominent nucleus. The MMC undergoes meiotic division. which results in the production of four haploid megaspores, arranged generally in the form of a linear tetrad.
Female gametophyte or Embryo sac: Only one of the megaspores is functional while the other three degenerate. The functional megaspore develops into the female gametophyte (embryo sac).
Pollination is the process of transferring pollen from the stamens to the stigmatic surface in angiosperms or the micropyle region of the ovule in gymnosperms. Depending on the source of pollen, pollination can be divided into three types.
Pollen transfer can be facilitated by the aid of abiotic (wind, water), abiotic (insects, birds, mammals).In some cases, pollen is transferred simply by gravity and the proximity of the anthers to the stigma.
Both wind and water pollinated flowers are not very colourful and do not produce nectar.
3. Zoophily It is a mode of pollination in which the biotic agents bring about pollination in flowering plants. Zoophily has several subtypes eg. Entomophily (by insects) malacophily (by snails ) chiropterophily (by Bats), ornithophilly (by birds eg. Humming bird), myrmecophily (by ants), anthrophily (by Humans).
Flower traits associated with different pollination agents
Advantages and Disadvantages of Cross Pollination
1. A number of plants are self-sterile, that is, the pollen grains cannot complete growth on the stigma of the same flower due to mutual inhibition or incompatibility, e.g., many crucifers, solanaceous plants. Several plants are pre-potent, that is, pollen grains of another flower germinate more readily and rapidly over the stigma than the pollen grains of the same flower, e.g., Grape, Apple. Such plants of economic interest give higher yield only if their biotic pollinators like bees are available along-with plants of different varieties or descent
2. Cross pollination introduces genetic re-combinations and hence variations in the progeny.
3. Cross pollination increases the adaptability of the offspring towards changes in the environment.
4. It makes the organisms better fitted in the struggle for existence.
5. The plants produced through cross pollination are more resistant to diseases.
6. The seeds produced are usually larger and the offspring have characters better than the parents due to the phenomenon of hybrid vigour.
7. New and more useful varieties can be produced through cross pollination.
8. The defective characters of the race are eliminated and replaced by better characters.
9. Yield never falls below an average minimum.
1. It is highly wasteful because plants have to produce a larger number of pollen grains and other accessory structures in order to suit the various pollinating agencies.
2. A factor of chance is always involved in cross .pollination.
3. It is less economical.
4. Some undesirable characters may creep in the race.
5. The very good characters of the race are likely to be spoiled.
As continued self-pollination result in inbreeding depression, flowering plants have developed many devices to discourage self- pollination and to encourage cross-pollination.
Artificial hybridisation is one of the major approaches of crop improvement programme. Here only the desired pollen grains are used for pollination and the stigma is protected from contamination (unwanted pollen). This is achieved by emasculation and bagging techniques. Anthers from the flower bud before the anther dehisces using a pair of forceps is necessary. This step is referred to as emasculation.
Ref: NCERT Biology for Class 12
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Hello! My name is Arunabha Banerjee, and I am the mind behind Biologiks. Leaning new things and teaching biology are my hobbies and passion, it is a continuous journey, and I welcome you all to join with me