Showing posts with label Medical Essays. Show all posts
Showing posts with label Medical Essays. Show all posts
Sunday, June 4, 2023
Why are Tasmanian Devils dying from oral cancer?
Before we get into this ailment, let us understand what these Tasmanian devils are - a Tasmanian devil is a well-built marsupial with a large head and powerful jaws; they have black fur and they are not found anywhere else in the world except in Tasmania. They are lethargic and slow-moving but aggressive and feed mainly on carrion.
The Tasmanian devil is the world’s largest living carnivorous marsupial. It is about the size of a small dog, Tasmanian devils are well known for their piercing nocturnal shrieks and their strong jaws. They are found only on the island of Tasmania, to the south of the mainland of Australia. Being marsupial mammals, Tasmanian devils give birth to tiny and underdeveloped young, completing their development in the mother’s pouch.
The Devil Facial Tumour Disease (DFTD) is a distinctive form of transferable cancer which harms its victims by causing tumours to grow around the face. These tumours interfere with their feeding patterns and lead ultimately to starvation. The lack of genetic variation in Tasmanian devil population leaves them particularly vulnerable to mass infection. Hence, the disease has eradicated a large percentage of Tasmanian devils, inflicting havoc in the survival of this already endangered species.
Perhaps no animal is better suited to its name than the Tasmanian devil. While it might look cuddly; in reality, this animal is quite the opposite. With the strongest bite of any mammal and a wicked blood-curdling scream, the Tasmanian devil is a ferocious creature which is known to assault animals many times its size. The irony is that even this devil is no match for its supreme enemy - an unusual and contagious face cancer, wrecking the population.
The first glimpse of this mysterious disease was given about two decades ago when people sighted large tumours on Tasmanian devils’ faces. They began to grow common. The news channels then started reporting that in the past twenty years; a third of their population had already died from this mysterious illness. The tumours were growing at a rapid and uncontrollable rate until they were noticed. The tumours were slowly covering their mouths and eyes and were giving indication that this could be cancerous. Neither the people living in Tasmania were able to figure nor were the scientists there able to determine the cause of such large tumours that were pervasive and growing fast.
Usually, cancer starts as a result of a single mutation or a change to a section of DNA (Deoxyribonucleic Acid). Most mutations are safe but often; they can cause a cell to grow and divide in an uncontrollable manner. This unrestricted enlargement causes the rogue cells to amass, forming the masses that we recognise as cancerous tumors. As cancer cells continually grow and divide, they tend to get more and more mutations in their DNA, resulting in tumors that give birth to a broader landscape of mutations. However, as mutations are considered random events, cancer often looks different in each individual. For example, two people having breast cancer may have tumors with completely different armoury of mutations. This is what makes the case of the Tasmanian devil so puzzling. It is almost impossible for so many of these animals to independently develop similar type of cancer so quickly through the classical mutation technique.
Even more intriguing is that every tumor sample has shown the same pattern of alterations in the Tasmanian devils’ chromosomes. This finding was quite odd, especially compared to how cancer has been generally shown to appear through a series of random mutations to DNA. The fact that all Tasmanian devil samples showed the same irregular chromosome patterns made researchers suspect that the devils were not suffering from a typical type of cancer as it would be nearly impossible for so many creatures to grow with the same exact mutations in their DNA. Instead, the lethal cancer spreading through their population might be infectious, spreading from one animal to another through bites to the face during sessions of fighting.
Intriguingly, the cancer affecting the Tasmanian devils showed no sign of viral transmission and the similarity among tumors did not support the mutation model. How this is then spreading from one animal to another? The answer may lie in what is called the MHC or Major Histo-compatibility Complex. The immune system has various ways of protecting the body against invasion by viruses, bacteria and parasites and any intrusive or cancerous cells. The first line of defense is built up by an inborn immune response made up of barriers like skin, tears, saliva and mucus. This is followed by defensive mechanisms built up by adaptive immune reactions that are more specific for the intruder. Adaptive immunity includes both a humoral response (macro-molecules) produced by antibodies and a cell-mediated reaction produced by T-cells that have the ability to destroy other cells. The cell-mediated adaptive immune reaction is synchronised by the Major Histo-compatibility Complex (MHC). It is called that because it is responsible for the rejection of graft or tissue compatibility.
As per reports, compared with the figures of Tasmanian devils in the past decade, almost sixty percent of their population has been destroyed by this disease. From the time of the initial discovery of DFT1, a second mutation has arisen as a variation in the form of DFT2 and has been devastating their population.
There is a very fine article written by Sharon Guynup in Mongabay magazine, which will help throw up better light on this issue facing the Tasmanian devils. Here is the link: https://news.mongabay.com/2021/10/in-harms-way-our-actions-put-people-and-wildlife-at-risk-of-disease/. This article elaborates on facts like how infectious diseases such as these pose a grave threat to not only Tasmanian devils but also chimpanzees, tigers, African wild dogs and Ethiopian wolves. Some viral diseases are being spread by humans, other domestic animals and livestock and this can culminate in giving a knockout punch to already endangered species that are bordering on extinction’s edge.
Not many people realize that a collection of humans, pigs, cows, dogs or chickens into wild areas can bring in further risk of the already endangered species. Somewhere along the line, man has had a broken relationship with nature in its wild patches. Corporate greed has also proved that the rich are quite separate from the rest of the species on earth. Activity of rich corporate thinkers has altered natural systems on earth in a rapid way. It has been so dramatic in the last few decades that it has brought in a new geological eon. These changes include deforestation which has gone out of control, farming, ranching, international travel, global commerce and wildlife trade with the help of poachers has affected climate change and has also helped spread diseases. Why does this happen? It is because such activities bring livestock, people and wildlife into contact, exposing all concerned to viruses and bacteria. Often, the ones suffering lack immunity in a rapidly warming world. Ticks, mosquitoes and several other parasitic carriers of diseases have an expanded range now, bringing debilitating ailments along with them. These changes have also helped new diseases to appear and spread to newer areas. This may lead perhaps to outbreaks soaring in the future. We have already seen recently how a pandemic could impact the whole ecosystem of this planet. Paradoxically, the ecosystem benefits when the dark satanic mills run to less than their optimal range and people are not polluting the atmosphere with carbon monoxide.
Here is the ominous part! Roughly around seventy per cent of all the growing and re-emerging pathogens are becoming zoonotic diseases that are transmitted from animals to humans. We have no idea when the next threat or the next Disease X will strike and when. This is also the sentiment shared by the Director of the World Health Organisation, Tedros Adhanom Ghebreyesus when he voiced the same at a meeting concerned with global animal health. Most infectious viruses are emerging from tropical areas which are also home to a rich variety of species and the volume of pathogens they can host and these areas are China, parts of Southeast Asia, Africa and India.
We simply have to face the fact that we have to live with diseases as they have become a part of this natural world. Bacteria and viruses have become interwoven into our ecosystems in a varied environment where indigenous residents have now evolved immune systems which prevent high rates of infection and subsequent deaths. Ecosystems have become intact and they maintain equilibrium. For example, as per Rick Ostfeld, a disease ecologist at Cary Institute of Ecosystem Studies in Millbrook, New York, USA, the web of life is thriving in tropical forests and also keeping hosts of diseases like rodents in decent check.
Coming back to our main focus, the Tasmanian devil facial tumour disease involves a couple of independent transmissible cancerous cells which have killed a majority of these species. These cells are originating from Schwann cells and spread between them as they bite each other as that is a common kind of behaviour during their mating season. DFT1 and DFT2 spread as a result of direct contact between them in situations involving fights over food and mates.
It is a point to be noted that like most other cancer remedial care, there is no satisfactory treatment procedures for DFT1 and DFT2. Several chemotherapeutic medicines have been on trial for DFT1 but not even one has shown any real efficacy towards treating this disease. Preliminary trials of immunotherapy have shown better promise in case of DFT1.
So, what is actually been done to save these Tasmanian devils. The government of Australia has started a funded initiative with the aim of saving this species. Research is being directed that will help understand the cause of these growing tumours. The main objective is to develop a vaccine; and if not, at least some form of intervention or therapy.
Sunday, January 31, 2021
Immune complex hypersensitivity (Type III) reactions
Type III hypersensitivity occurs when antigen and antibody complexes accumulate when they are not adequately cleared by immune cells. They give rise to an inflammatory response and attract leukocytes.
Type II immune complex hypersensitivity will occur when there is an excess of antigen leading to complexes that are not cleared from the circulation. It involves soluble antigens that are not bound to cell surfaces unlike those found in Type II hypersensitivity. When these antigens bind the antibodies, immune complexes of various sizes will form. Large complexes can be cleared by macrophages but they have difficulty in the disposal of small immune complexes. These immune complexes will insert themselves into smaller blood vessels and joints causing symptoms. Such depositions in tissues often stimulate an inflammatory response and they can cause damage wherever they precipitate.
Friday, January 1, 2021
Otolaryngology
Define Sound
Sound is a form of energy that is produced by vibrating objects. A sound wave is made up of compression and rarefaction of molecules of media like solid, liquid or air in which the sound waves travel. Velocity of sound is different in each media. In the air, sound travels at a speed of 1120 feet per second at a temperature of twenty degrees Centigrade. It is faster than this through liquids and much faster through the solid medium.
What do you understand by the frequency of sound?
It is the number of cycles per second. The unit of frequency of sound is measured in Hertz (Hz). This unit is named after the German scientist, Heinrich Rudolf Hertz. A sound wave of 1000 Hz will indicate 1000 cycles per second.
What is complex sound? Give an example
It is sound made with more than one frequency. Human voice is example of complex sound. The higher the frequency of sound, the greater will be the pitch. The complex sound has a fundamental frequency which the lowest at which a source vibrates. All frequencies above that particular tone are called overtones. These overtones establish the quality of the timbre of sound.
What is a decibel in terms of measurement of sound?
A decibel (dB) is measured as one-tenth of a bel unit named after Alexander Graham Bell who invented the telephone. The decibel represents a logarithmic ratio between two sounds – that is the sound being described along with the reference sound. Too many decibels constitute noise which can be defined as an aperiodic complex sound. There are three types of noise levels – White Noise, Narrow Band Noise and Speech Noise.
What is the dynamic range of sound?
It is the difference between the most comfortable level of sound and the discomfort level which can be measured in terms of decibel loudness. The dynamic range of sound is reduced in patients who have positive recruitment phenomenon in the case of a cochlear type of hearing loss. The sound level meter is the instrument used to measure level of noise and other sounds.
Sunday, November 1, 2020
Atrophic Rhinitis
What is atrophic rhinitis?
Atrophic rhinitis is a chronic nasal condition that is characterised by the formation of thick dry crusts in the nasal cavity. It results from progressive wasting away or decreasing in size (atrophy) of the mucous nasal lining (mucosa) and its underlying bone. It also affects the glands and turbinate bones. Special forms of chronic atrophic rhinitis are rhinitis sicca anterior and ozaena.
Etiology
• Hereditary factors
• Endocrinal imbalance - the disease tends to start at puberty and mostly involves females
• Racial factors - whites are more susceptible than natives of equatorial Africa
• Nutritional deficiency in vitamins A , D or iron
• Autoimmune factors - viral infection may trigger antigenicity of the nasal mucosa
Symptoms
• Most commonly seen in females
• Reported among patients from lower socioeconomic groups
• The nasal cavities become roomy and are filled with foul smelling crusts which are black or dark green and dry, making expiration painful and difficult.
• Microorganisms are known to multiply and produce a foul smell from the nose, though the patients may not be aware of this, because their elements (responsible for the perception of smell) have become atrophied. This is called merciful anosmia.
• Patients usually complain of nasal obstruction despite the roomy nasal cavity, which can be caused either by the obstruction produced by the discharge in the nose, or as a result of sensory loss due to atrophy of nerves in the nose, so the patient is unaware of the air flow.
• Bleeding from the nose, also called epistaxis, may occur when the dried discharge (crusts) are removed.
• Septal perforation and dermatitis of nasal vestibule can occur. The nose may show a saddle-nose deformity.
Management
Treatment of atrophic rhinitis can be either medical or surgical.
Medical measures include:
• Nasal irrigation using normal saline
• Removal of crusts using alkaline nasal solutions prepared by dissolving a spoonful of powder containing one part sodium bicarbonate, one part sodium biborate and two part sodium chloride.
• 25% glucose in glycerine can be applied to the nasal mucosa to inhibit the growth of proteolytic organisms which produce foul smell
• Local antibiotics, such as chloromycetine
• Vitamin D(Kemicetine)
• Systemic streptomycin (1g/day) against Klebsiella organisms.
Surgical interventions include:
• Modified Young's operation
• Narrowing of nasal cavities, sub-mucosal injection of Teflon paste, section and medial displacement of the lateral wall of the nose
• Transposition of parotid duct to maxillary sinus or nasal mucosa
Wednesday, September 30, 2020
Assessment of Hearing - Otolaryngology
What are the three types of hearing loss?
1. Conductive hearing loss – It is caused by any disease process that interferes with the conduction of sound from external ear to the stapediovestibular joint. The cause may lie in the external ear or the Eustachian tube in the form of obstructions or in the tympanic membrane in the form of perforation or in the middle ear in the form of fluids or in the ossicles in the form of fixation or disruption.
2. Sensorineural hearing loss - This is caused by lesions of the sensory type of the cochlea or of the cranial nerve 8 and its central connections of the neural type. When the hearing loss is due to lesions of cranial nerve 8, it is known as retrocochlear and when it is because of the lesions of the central auditory connections, it is referred to as central deafness.
3. Mixed hearing loss – In this kind of hearing loss, both sensorineural and conductive elements of deafness are present in the same ear. There is an air-bone gap that indicates the conductive element and impairment of bone conduction that triggers sensorineural loss. Mixed hearing loss is found in cases of chronic suppurative otitis media and otosclerosis.
What four factors are important while assessing the auditory functions?
1. Type of hearing loss – whether it is conductive, sensorineural or mixed.
2. Cause of hearing loss – it may be congenital or traumatic or it could be infection or an auto-immune process.
3. Degree of hearing loss – It could be mild or moderate or it could be severe or total.
4. Site of the lesion – If it is conductive hearing loss, the lesion may be at the external ear or the tympanic membrane or it could be at the middle ear or the Eustachian tube. Tympanometry is helpful in finding the site of lesions. If it is a sensorineural loss, it is to be determined whether the lesion is cochlear or central or retrocochlear. Often special tests of hearing are needed to differentiate the types of these lesions.
How is hearing tested?
It is done through clinical or audiometric tests.
What are the four major clinical tests of hearing?
1. Finger Friction Test – It is a quick method of screening and it involves rubbing and snapping the thumb and a finger by positioning them close to the ear of the patient.
2. Watch Test – A watch that clicks is brought close to the ear of the patient and the distance at which it is heard is measured.
3. Speech or Voice Tests – For the purpose of the test, the patient has to hear a conversation at a distance of forty feet in quiet surroundings. Its disadvantage is the lack of standardisation in intensity.
4. Tuning Fork Tests – They are done with tuning forks of different frequencies. The average frequency is 512 Hz. The tuning fork is activated by striking it gently against the examiner’s elbow or heel of hand. Tuning forks of lower frequencies than 512 Hz produce sense of bone vibration. A vibrating fork is placed vertically in line with the meatus to test air conduction and it is kept about two centimetres away from the opening of the external auditory canal. The sound waves are transmitted through the tympanic membrane. Middle ear and the ossicles to the inner ear. In order to test bone conduction, the foot plate of the vibrating tuning fork is placed on the mastoid bone. Cochlea is stimulated directly by the vibrations conducted through the skull bones.
What are some of the important and clinically useful tuning fork tests?
1. Rinne – Air conduction of the ear is compared with its bone conduction. A vibrating tuning fork is placed on the patient’s mastoid and when hearing stops, it is brought besides the meatus. If he still hears, air conduction is more than bone conduction. Rinne’s test can be concluded as false negative in severe unilateral sensorineural hearing loss. The patient does not hear any sound of the tuning fork by air conduction but responds to bone conduction.
2. Weber’s – A vibrating tuning fork is placed in the middle of the forehead and the patient is asked in which ear he or she can hear the sound. Normally, it is heard equally in both ears. It is lateralized to the worse ear in conductive deafness and to the better ear in sensorineural deafness.
3. Gelle’s – It is a test of bone conduction and examines the effect of increased air pressure in ear canal on hearing. It is performed by placing a vibrating tuning fork on the mastoid while changes in air pressure in ear canal are brought about by Siegel’s speculum.
What are the four types of audiometry tests and explain briefly, giving details about tympanometry as part of impedance test
1. Pure Tone Audiometry- Audiometer is used to produce pure tones, Their intensity can be increased or decreased by 5 dB steps and the amount of intensity that has to be raised above the normal level is a measure of the degree of hearing impairment at that frequency. It is charted in the form of a graph called audiogram. It is used to measure the degree and type of hearing loss, prescription of hearing aid and degree of handicap for medico-legal purposes
2. Speech Audiometry- The patient’s ability to hear and understand speech is measured. The two parameters used are speech reception threshold and discrimination score.
3. Bekesy Audiometry- It is a self-recording audiometry where various pure tone frequencies automatically move from low to high while the patient controls the intensity through a device that indicates Type 1 – Type V degree.
4. Impedance Audiometry- There are two tests that make up this category. They are tympanometry and acoustic reflex measurements. Tympanometry is based on a simple principle that dwells on when a sound strikes the tympanic membrane; some of its energy is absorbed while the remainder is reflected. It helps in finding the degree of compliance or stiffness of the tympanic membrane to show the health of the middle ear. Five types of tympanograms are Type A, Type As, Type AD, Type B and Type C with the range being Type A as normal and Type C as maximum compliance.
Monday, June 1, 2020
Slowing Down the Ticking of Biological Clocks in Women
Wednesday, August 22, 2018
Peptic Ulcer Drugs Classification Therapeutic Utility
Sunday, February 25, 2018
Best Treatment for Oily Skin
Monday, February 19, 2018
Ten Soups that are Ideal when Dieting
Hashimoto Thyroiditis
Ten Most Likely Causes of Low Back Pain
Thursday, February 8, 2018
Garlic supports Healthy Dieting
Dopamine
Tuesday, December 12, 2017
Top Foods that Burn Fat and are Good for Weight Loss
Four Examples of Hyperplasia
Saturday, December 2, 2017
Five Reasons you do not lose Fat when Dieting
Wednesday, November 29, 2017
Holistic Dieting and Top Ten Considerations about it
The Advantages of taking Copper Supplements
Wednesday, November 22, 2017
Classification of Beta Lactam Antibiotics and Mechanism of Action of Benzyl Penicillin
Tuesday, October 24, 2017
Etiopathogenesis of Diabetes Mellitus
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