Zinc ‘sparks’ fly from egg within minutes of fertilization

NIH-funded study of animal eggs reveals major role for metal

At fertilization, a massive release of the metal zinc appears to set the fertilized egg cell on the path to dividing and growing into an embryo, according to the results of animal studies supported by the National Institutes of Health.

The zinc discharge follows the egg cell’s steady accumulation of zinc atoms in the developmental stages before fertilization. The researchers documented the discharge by bathing the eggs in a solution that gives off light when exposed to zinc. They referred to the zinc discharge and accompanying light flash as zinc sparks.
“The discovery of egg cells’ massive intake and later release of zinc defines a new role for this element in biology,” said Louis DePaolo, chief of the Reproductive Sciences Branch at the Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD), one of the NIH institutes supporting the study. “We anticipate the findings will one day lead to information useful for the treatment of infertility as well as the development of new ways to prevent fertilization from occurring.”
The study’s authors suggest that zinc acts as a switch, turning off the process of cell division while the egg matures and turning it on again after fertilization.

“These findings suggest zinc is essential for developing a healthy egg and, ultimately, a healthy embryo,” said Teresa Woodruff, Ph.D., one of the article’s senior authors.

The study’s first author is Alison M. Kim, Ph.D., of Northwestern University, Evanston, Ill. The other authors are Miranda L. Bernhardt, Betty Y. Kong, Richard W. Ahn, Dr. Woodruff and Thomas V. O’Halloran, Ph.D., of Northwestern, and Stefan Vogt, Ph.D., of Argonne National Laboratory, Washington, D.C.

Their findings appear in the July issue of ACS Chemical Biology.
In this study, the researchers observed egg cells from mice and from monkeys. To conduct the study, they devised a microscope that would allow them to view the concentration and distribution of zinc atoms in individual cells. With the aid of the chemical that gives off light when exposed to zinc, the researchers documented the first zinc sparks 20 minutes after fertilization. Most fertilized eggs released two or three rounds of sparks, but the researchers saw as few as one and as many as five within the first two hours after fertilization. The sparks flared every 10 minutes, on average.

Previous research had shown that fertilization triggers cyclical changes in the level of calcium in the egg cell.

The researchers noted that the zinc sparks always occurred after a peak in calcium levels inside the cell.
“The number, timing and intensity of these sparks could tell us something important about the quality of the egg and will be an important area for future research,” said Dr. O’Halloran, the article’s other senior author. “It’s may also be worth investigating whether the amount of zinc in a woman’s diet plays a role in fertility.”

Additional experiments helped confirm a role for zinc in the fertilization process. Typically, once the egg is released from the ovary, it must get rid of excess chromosomes in two stages as it prepares to fuse with the sperm. The team’s earlier research showed that the early accumulation of zinc is essential for properly completing the first stage, Dr. O’Halloran explained. The latest results suggest that zinc may act as a brake in between these stages, as the egg awaits fertilization. If the cell is fertilized, the zinc release appears to lift the brake. The cell discards its excess genetic material and begins to divide.

The researchers also showed that even unfertilized eggs would start to divide if zinc levels were artificially reduced, mimicking release. In addition, when fertilized cells were forced to take on additional zinc, the process was reversed.

“We have shown that zinc appears to regulate this precisely calibrated, intricate process,” Dr. Woodruff said. “The findings give us new insights into what these cells need to grow and mature properly.”
The NICHD sponsors research on development, before and after birth; maternal, child, and family health; reproductive biology and population issues; and medical rehabilitation. For more information, visit the Institute’s website at http://www.nichd.nih.gov/.

About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.

NIH tips for older adults to combat heat-related illnesses

Risk of heat-related problems increases with age

Older people can face risks related to hot weather. As people age, their bodies lose some ability to adapt to heat. They may have medical conditions that are worsened by heat. And their medications could reduce their ability to respond to heat.
The National Institute on Aging (NIA), part of the National Institutes of Health, has some advice for helping older people avoid heat-related illnesses, known collectively as hyperthermia.
Hyperthermia occurs when the body overheats. Conditions involving hyperthermia have different names, including heat stroke, heat fatigue, heat syncope (lightheadedness or fainting in the heat), heat cramps and heat exhaustion.
Health-related factors that may increase the risk of hyperthermia include:

• Pre-existing diseases such as congestive heart failure, diabetes and chronic obstructive pulmonary disease
• Decreased ability to move around
• Dementia or cognitive impairment
• Certain medications that may cause dehydration or that may affect the responses to heat by the heart, blood vessels or sweat glands.
• Being substantially overweight
• Drinking alcoholic beverages
• Being dehydrated
• Age-related changes in the skin, such as decreased functioning of small blood vessels and sweat glands

Lifestyle factors that can also increase the risk of hyperthermia include hot living quarters, lack of transportation, overdressing, visiting overcrowded places, and not understanding how to respond to weather conditions. Older people, particularly those at special risk, should pay attention to any air pollution alert in effect. People without fans or air conditioners should go to shopping malls, movie theaters, libraries or other places with air conditioning. In addition, they can visit cooling centers which are often provided by government agencies, religious groups and social service organizations in many communities.
Heat stroke is an advanced form of hyperthermia. It occurs when the body is overwhelmed by heat and unable to control its temperature. In heat stroke, the body temperature is at least 104 degrees Fahrenheit. Someone with heat stroke may have a strong rapid pulse, lack of sweating, dry flushed skin, faintness, staggering and mental status changes such as confusion, combativeness, disorientation or even coma. Seek immediate medical attention for a person with any of these symptoms, especially an older adult.
If you suspect that someone is suffering from a heat-related illness:

• Move them into an air conditioned or other cool place
• Urge them to lie down and rest
• Remove or loosen tight-fitting or heavy clothing
• Encourage them to drink water or juices if they are able to drink without choking, but avoid alcohol and caffeine
• Apply cold water, ice packs or cold wet cloths to the skin.
• Get medical assistance as soon as possible.

The Low Income Home Energy Assistance Program (LIHEAP) within the Administration for Children and Families in the U.S. Department of Health and Human Services helps eligible households pay for home cooling and heating costs. Individuals interested in applying for assistance should contact their local or state LIHEAP agency. For more information, go to www.acf.hhs.gov/programs/ocs/liheap/ or www.acf.hhs.gov/programs/ocs/liheap/brochure/brochure.html.
For a free copy of the NIA’s AgePage on hyperthermia in English or in Spanish, contact the NIA Information Center at 1-800-222-2225 or go to http://www.niapublications.org/agepages/hyperther.asp, or www.niapublications.org/agepages/hyperther-sp.asp for the Spanish-language version.
The NIA leads the federal government effort conducting and supporting research on aging and the health and well-being of older people. The Institute’s broad scientific program seeks to understand the nature of aging and to extend the healthy, active years of life. For more information on research, aging, and health, go to www.nia.nih.gov.
About the National Institutes of Health (NIH): NIH, the nation's medical research agency, includes 27 Institutes and Centers and is a component of the U.S. Department of Health and Human Services. NIH is the primary federal agency conducting and supporting basic, clinical, and translational medical research, and is investigating the causes, treatments, and cures for both common and rare diseases. For more information about NIH and its programs, visit www.nih.gov.