Effects of stress on sperm

Children of stressed fathers are at greater risk of developing PTSD and depression, according to a new study. Researchers found life's pressures can change the DNA of a man's sperm - leading to brain development changes in his yet unborn baby. It's widely known that a mother's environment during pregnancy, including factors such as poor diet, stress and infection, can negatively impact the offspring.

Learning how a father's behavior and environment can impact his child's development could lead to the detection and prevention of many mental health disorders. Researchers have known for years that stress can increase the risk of mental disorders,' Dr Tracy Bale, professor of neuroscience at the University of Maryland School of Medicine, told Daily Mail Online. 'What’s interesting here is that we are finding intergenerational effects.'

Researchers, led by Dr Bale, conducted a mice experiment to examine how a father's lifestyle impacts his children. Previously, the team has found male mice experiencing chronic periods of mild stress passed down genetic coding for a less effective hormonal response to stress in children. Three major hormones are released by the nervous system when the body is under stress. These are adrenaline, cortisol and norepinephrine. Collectively, these hormones send human bodies into ''fight''mode, which is important to the body's ability to cope with the effects of stress.

Stress resulted in changes in sperms genetic material known as microRNA, which plays a key role in which genes become functional proteins. These changes in stress reactivity have been linked to some mental disorders, including depression and PTSD.

In the new study, presented at the 2018 AAAS annual meeting in Austin, Texas, Dr Bale and her colleagues unraveled new details about the microRNA changes in the sperm. The caput epididymis, the structure where sperm matures, release vesicles which contain microRNA that can fuse with sperm to change its cargo delivered to the egg. When males mice were stressed, the caput epididymis responded by altering the content of these vesicles.

This suggests even mild environmental stress, such as workplace stress, can have a significant impact on the development and potentially the health of future offspring. This is through a process known as epigenetics where DNA is changed through lifestyle factors such as diet, exercise - or even stress. Scientists have known a mother's environment during pregnancy can damage a fetus by diet, stress or infection affecting the expression of certain genes in the same way.

Father's stress can affect offspring development by altering important aspects of his sperm. Her previous studies on the placenta have revealed novel sex differences during pregnancy that may predict increased pre-natal risk for neurodevelopmental disorders in males. Historically, most research on how a parent's lifestyle, behavior and environment can affect their children has focused on the mother. But scientists have recently been paying increasing attention to how a father's health impacts his children.
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Effects of maternal stress on fetus

Maternal stress during the second trimester of pregnancy may influence the nervous system of the developing child, both before and after birth, and may have subtle effects on temperament, resulting in less smiling and engagement, as well as diminished ability to regulate emotions. Researchers looked at the stress levels of many low-to-middle-income women who were between 12 and 24 weeks pregnant. The researchers followed the women throughout pregnancy and after delivery, and conducted a test to compare their reported stress levels during pregnancy with objective levels of stress in their 6-month-old offspring.

In the test, the infants' cardiac function was monitored while the mothers were instructed to look at the infant's face but not interact with or touch them for two minutes following a brief play session. The mothers reported the number of stressful life events they had experienced during pregnancy, which included illness, relationship problems, housing difficulties and legal issues. The babies of mothers with the highest number of these stressful life events who completed the testing were 22 percent more reactive than the infants of mothers reporting the lowest number of stressful life events. They also recovered less quickly from the stressor, demonstrating lower resilience.

High reactivity, which is assessed by measuring the variability in the heart rate in conjunction with breathing, is indicative of a stronger decrease in parasympathetic nervous system activity in response to challenge, The parasympathetic nervous system enables the body to rest and digest food, by slowing the heart rate and increasing intestinal and glandular activity. Being highly reactive places children at risk for a range of psychopathological problems, particularly anxiety and depression, as well as externalizing problems, such as disruptive behavior, especially if they experience adverse family and school environments.

However, in an optimal environment with few adversities, children with higher stress reactivity don't have their stress response triggered too often and may exhibit better-than-average social skills and emotional and behavioral well-being, because greater reactivity can make them more sensitive to the benefits of positive relationships and experiences in their environments. Those who had higher levels of perceived stress in pregnancy and post-delivery, had babies with temperamental surgency levels that were 8 percent lower than those babies of mothers in the lower third, who reported less perceived stress in pregnancy and post-delivery.

Surgency includes traits such as willingness to approach and engage with the outside world, as well as laughter and smiles. These same babies born to the highly-stressed mothers were also found to have eight percent lower levels of self-regulation, the ability to manage emotions – such as soothing themselves in periods of high stress  compared with the babies of mothers with less perceived stress during pregnancy and post-delivery. This combination of lower surgency and lower self-regulation can place individuals at added risk for depression, anxiety and difficulties with their social relationships.
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Breastmilk prevents food allergy

A mother's diet can protect nursing newborns against food allergies. In mice, milk from mothers exposed to egg protein gave protection against egg allergy to the mothers and offspring, but also to fostered newborns whose birth mothers had not received egg. Newborns gained an insignificant degree of protection from mothers who were exposed to egg during pregnancy but did not breastfeed them. The protective effect was strongest when the newborns were born to and nursed by mothers who were exposed to egg before and during pregnancy and breastfeeding.

 Pregnant and breastfeeding mothers were sometimes cautioned against consuming foods that commonly cause allergy, such as milk, egg, peanut, tree nuts, soy, wheat, fish and shellfish. More recently, feeding peanut foods to infants at high risk for peanut allergy was shown to decrease, not increase, the babies' likelihood of developing allergy to peanut. Allergists now recommend that, unless mothers already have diagnosed food allergies, they should not avoid allergenic foods while pregnant and nursing. Mothers are free to eat a healthy and diverse diet throughout pregnancy and while breastfeeding. Eating a range of nutritious foods during pregnancy and breastfeeding will not promote food allergies in developing babies, and may protect them from food allergy.

Maternal and early childhood diets do not cause food allergies in children. Most children do not develop food allergies, regardless of how they are fed., while some children develop allergies even when fed an optimal diet. The food allergy protections described in the study are dependent on specific proteins, some provided by the mother, others by the offspring. By identifying these proteins and proposing a mechanism through which mother and offspring contribute to the development of food tolerance in the newborn mouse, the research opens new opportunities to study how the protections break down in the case of food allergy and how such breakdowns might be prevented.

Preventing food allergy is critical because there are no approved treatments for this serious and potentially life-threatening condition. The mouse study found that when a nursing mother is exposed to a food protein, her milk contains complexes of the food protein combined with her antibodies, which are transferred to the offspring through breastfeeding. Aided by a protein in the offspring's gut lining and some immune cells, the food protein-antibody complexes are taken up and introduced to the offspring's developing immune system, triggering the production of protective cells that suppress allergic reactions to the food. These protective cells persist after antibodies from the mother are gone, promoting long-term tolerance to the food. A similar mechanism may offer protection to human infants.
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Eggs can select semen

According to the latest research, female's eggs are able to select sperm with the best genes to ensure the healthiest offspring. Semen does not appear to have the same ability to detect bad genes, this shows that fertilisation is not random and specific pairings between certain eggs and sperm are more common than others. Researchers bred female mice carrying one normal and one mutant copy of a gene that increased the chance of getting testicular cancer.

 The resulting offspring followed Mendel's rules and there was a random dispersal of the mutated form among offspring. Researchers reversed the breeding- gave males the mutant copy of the cancer gene while the females had the normal version. Only 27 per cent of the offspring had the mutant variant, compared to the 75 per cent. Researchers found no evidence the mutated mice embryos were dying shortly after fertilisation, rather they were never fertilised.

The rate of metabolism folic acid - which is an important signalling molecule - is different in sperm and eggs. Research has revealed that these molecules play an important role in fertilisation. Changes in these signals may impact how much sperm and egg are attracted to one another. When sperm from multiple males arrive at an egg concurrently, eggs are able to choose the sperm whose recognition proteins are best suited for healthy fertilization. This selection process can spur the evolution of new recognition proteins, eventually resulting in reproductive isolation and, in some cases, the creation of new species altogether.
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Naturally acquired immunity against Zika virus

During their study of Zika infection in pregnant mice, the researchers built-up immunity in previously infected mothers that continued into pregnancy and protected fetal tissues. Because the mothers had already cleared their non-symptomatic Zika infections, they developed high levels of protective immunoglobulin antibodies against the virus that researchers found in the animals. Detection of these protective antibodies points to the possibility of developing diagnostic tests to identify naturally immune women and distinguish them from women at high risk of infection.

The ability to identify high-risk women would help develop focused therapeutic strategies for prevention, combining protective antibodies with an eventual vaccine, which could synergistically provide more a robust level of protection against Zika. Built-up immunoglobulin antibodies protect against Zika infection in mothers and their developing fetal offspring.

Researchers said expectant mothers are susceptible to Zika infection compared to non-pregnant women. If the virus is active during pregnancy, it usually spreads to vital tissues of a developing fetus. Because Zika virus infection in healthy non-pregnant women is mostly asymptomatic, many women of reproductive age in high-risk regions have a cleared infection before pregnancy.

Susceptibility to Zika virus infection was markedly reduced in mice that had previously cleared a prior infection compared to those undergoing a first infection during pregnancy. Mice that didn't have prior Zika infections developed clinical symptoms and sharply increased levels of Zika virus in their blood, which spread to fetal tissues.

Zika virus could not be found in most of the baby mice from mothers with resolved infection prior to pregnancy. Protection found in Zika-resistant mice could be transferred to susceptible mice with Zika virus neutralizing antibodies found in the blood of mice with prior asymptomatic infection.
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Low protein diet for longevity

Having a low-protein diet early in life may help you live longer. A study found fruit flies which share more than two thirds of humans genes live twice as long when given minimal protein diet at tender age. A typical western diet is high in protein and fats from meat, diary, and eggs with red meat in linked to heart disease and cancer. There is an evidence that eating too much protein long-term can lead to an increased risk of osteoporosis and kidney problems.

The researchers also believe their findings could be explained because a low-protein diet produces less toxic lipids secreted by the skin. Health skin lipids form a natural barrier keeping out dirt, impurities and harmful chemicals that can accelerate ageing. Scientists used the fly drosophila melanogaster to understand how diet in early life acts to alter lifespan. These insects are used in lifespan experiments because it lives for only two to three months.

The team stressed that there was enough evidence to recommend pregnant women go on low-protein diets to boost their unborn child's health. There is evidence in humans and other mammals that a mother's diet can alter the risk of her offspring developing cardiovascular disease and diabetes later in life, but the genetic processes underlying this effect remain to be identified.
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Chemotherapy may have effects on intergenerational fertility

Chemotherapy treatment can damage the fertility of women and their children. The treatment can reduce the levels of fertility and chance of having children. Women and men are encouraged to freeze their eggs or sperm before treatment.

But when chemotherapy patients have children naturally, it was usually assumed that their ability to reproduce was unaffected. Children born to women who have had chemotherapy have 72 per cent fewer children of their own than members of the general population.

The effect seems to mainly affect women. Children of men who had chemotherapy treatment may have a similar number of children compared to members of the general population of the same age. Daughters of women who had chemotherapy had 71 per cent fewer children than the general population. Sons of female chemotherapy patients had 87 per cent fewer children.

 This may be caused by epigenetics or changes which can be compared to switches that turn on or off certain genes in the DNA passed on to a person’s offspring. Recent studies have found that, smoking causes epigenetic changes in DNA. Chemotherapy given to women may have intergenerational effects on fertility.
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Effects of father's diet on fetus

Father's diet before conception can impact newborn's health, low carbohydrate and high protein diet can make the fetus healthy. Experiments were performed on fruit flies and the results showed offspring were less likely to survive if their fathers consumed a poor diet of high carbohydrates and low protein.

The insects were used because they have 60 percent of human genes.
Researchers mated male fruit flies with females after they altered their diet.
Since fruit flies share similar genes to that of humans, the researchers believe the impacts of the bugs' diet would correlate with that of men.

The study claims that men who want to become fathers should have a diet consisting of fish, meat, vegetables and fruit while cutting out pasta, rice and white bread. Sugary foods such as sweets, cakes and biscuits should be avoided. Exposure to toxins can be passed from the father to his offspring through his semen. During the experiment, female fruit flies were fed the same diet while males had different ones consisting of yeast and sugars.

The insects ate different foods, from low to high concentrations of proteins, carbohydrates and calories. After some days the males were mated with two females. The results showed that embryos were more likely to survive if they had a father with a high protein and low carbohydrates diet. Mortality was highest for offspring of males given a high carbohydrate, low protein diet. Researchers also found a connection between the male's body condition and his offspring's mortality.
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Key regulator of male infertility

The protein complex known as Polycomb Repressive Complex 1 PRC1. PRC1 activates specific germline genes and the production of healthy sperm. It is responsible for production of health male sperm.

Male mammals are born with all the reproductive germline cells and inheritable genetics needed to make healthy fertile sperm and offspring. But the sperm isn't fertile at childhood.
PRC1 also blocks the specific genes and the activation of fertile sperm production until reproductive age.

Researchers show in their current study that when mice reach reproductive age, the PRC1 protein complex changes. It sheds reproductive germline gene components that block fertile sperm production and substitutes in a component that start spermatogenesis.

The repressor of sperm production, PRC1 also promotes gene activation to produce sperm at maturity. The scientists also found that when PRC1 is disrupted, such as in male mice bred to not express PRC1, the animals have smaller testes and are unable to produce healthy sperm or offspring.
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Female mosquitoes transmit Zika virus to their eggs

Zika virus has been found to cause a form of brain damage- microcephaly in newborns whose mothers were infected during pregnancy.

Researchers injected laboratory-reared A. aegypti with Zika virus. The mosquitoes were fed, and they started laying eggs after some days.

 The researchers collected and incubated the eggs and reared the hatched larvae to adult mosquitoes.

They discovered that the mosquitoes passed viruses on to their offspring, including dengue fever, yellow fever and zika virus.

Keep your environment clean, destroy mosquitoes' eggs to prevent mosquitoes from breeding and spreading of Zika virus.

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Alcohol effects on fetus

Alcohol can pass from the mother's blood into the fetus' blood. It can damage and affect the growth of the fetus' cells. It can damage the brain and spinal cord cells.

Researchers from Belgium and Australia assessed the drinking habits of more than 400 women during pregnancy and mapped the facial features of their offspring at the age of 1 year.

The team discovered that prenatal alcohol exposure - even at low levels - subtly influenced the formation of facial features in the womb, including the nose, chin, and eyes.

Alcohol consumption during pregnancy can cause physical and developmental problems for fetus, including low birthweight, learning disabilities, small head size, intellectual disabilities, and problems with vision and hearing.

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Father's lifestyle and diet affect the cognitive skills of his offspring

Scientists at the German Center for Neurodegenerative Disease have shown that if male rodents eat foods rich in vitamin B12, methionine and folic acid, their offspring will not perform well in memory test.

Child development is also affected by father's diet and lifestyle: if male rodents eat food rich in fats, their offspring may become diabetic.

Another group of rodents was given balanced diet, mated with female mice, their offspring was examined and their is clear difference between rodents that were fed with balanced diet and those fed with methyl donor-rich diet.

This shows that mother's diet is not the only cause of abnormality in offspring, paternal diet can affect learning skills in offspring.