Researchers: Some need to fear bats in our belfries

Health Scan: Environmental light pollution is linked to cancer; physical qualities may influence on how adult stem cells from bone marrow become differentiated.

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October 10, 2010 04:11
BATS DON’T deserve their bad reputations

bat 311. (photo credit: Detroit Free Press/MCT)

 
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Although bats have a bad public image, with superstitious people believing they suck the blood of humans and bring bad luck, they are hardly Draculas. In fact, they are quite benevolent and spend their nights munching on pesky mosquitoes and insects harmful to agriculture, pollinate flowers and spread seeds. However, they may also feed on fish, small mammals, songbirds and animal blood.

Researchers at Tel Aviv University zoology department’s mammal center, the Society for Prevention of Nature, Rambam Medical Center and others have been conducting studies for two decades on local species, which are mostly fruit bats. This included observation by staffers who lay on their their backs at the entrance to caves, count them manually as they enter and identify the species by monitoring the frequency of their voices and recording them digitally. They also catch some in nets to validate their identification. There have been projects to use bats as natural pest exterminators instead of using sprays and other poisons.

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Drs. Eran Levine, Amit Dolev and Idan Sholet, who wrote an article on the subject in the latest issue of Harefuah (the Hebrewlanguage journal of the Israel Medical Association), note that there has not been a single report of rabies spread by these flying mammals here. In addition, there have been no reports on other diseases spread by bats, they write. The public don’t know much about the handling of adult bats that are injured or babies that are unable to fly.

Handling a bat without proper gloves or experience almost always leads to bites or at least scratches with their sharp nails. In addition, they write, a bat captured during the day, when it can’t fly, may be ill. People are advised not to touch them.

The authors conclude the article with the story of a British Airways’ Boeing 767 that landed at Ben-Gurion Airport four years ago with a large hole in one of the wings. Inside were bits of fur and flesh from a bat that had collided during the jet’s takeoff. The species was a fruit bat called Eidolon helvum that lives neither in Israel nor England but is native to Africa and known to carry certain viruses and other pathogens. If a dog or wild animal had eaten the remains in Israel, the bat could have spread diseases to which the country had not been exposed. Thus Levine and colleagues urge caution about bats.

TURN OFF THE LIGHT

If you haven’t been persuaded to reduce your exposure to electric lighting at night following numerous studies showing that it increases the risk of cancer in both men and women, here is a new study from the University of Haifa’s Center for Interdisciplinary Chronobiological Research.



Light At Night (LAN) via high-power bulbs contributes “to environmental light pollution, which the study has shown is carcinogenic,” noted Prof. Abraham Haim, who headed the study.

Earlier studies in which he has participated have shown that people living in areas with more night-time illumination are more susceptible to prostate cancer and breast cancer. The researchers’ hypothesis was that LAN harms the production of melatonin, a hormone released from the pineal gland during the dark part of the 24-hour cycle and which is linked to the body’s cyclical nightday activity. When this hormone is suppressed, the prevalence of cancer rises.

The current study, in which Dr. Fuad Fares and Adina Yokler, Orna Harel and Hagit Schwimmer also participated, set out to establish or refute this hypothesis. Four groups of lab mice injected with cancerous cells were examined: those in one group were exposed to “long days” of 16 hours of light and eight hours of darkness, simulating exposure to artificial light beyond the natural number of light hours in a day; a second group were exposed to the same “long days” but were treated with melatonin; those in the third group were exposed to “short days” of eight light hours and 16 dark hours; and a fourth group were exposed to the same “short days” but during the dark hours were exposed to a half-hour interval of light.

The results show once again the clear link between LAN and cancer: the cancerous growths in mice exposed to “short days” were smallest, while those mice exposed to LAN during dark hours had larger growths and those exposed to “long days” even larger growths. Such prospective studies, more active than retrospective ones, can not be performed on humans, but are believed to be relevant to people.

The researchers say their results show that suppression of melatonin due to exposure to LAN is linked to the worrisome rise in the number of cancer patients over the past few years – but it is not yet clear what mechanism causes this. “Exposure to LAN disrupts our biological clock and affects the cyclical rhythm that has developed over hundreds of millions of years devoid of LAN. The dangers of light pollution are gaining public attention around the world, and the World Health Organization’s International Agency for Research on Cancer (IARC) has already classified working night shifts as a higher grade of cancer risk,” the researchers noted.

INFLUENCES ON STEM CELLS

Physical qualities – and not only chemical ones – may have an influence on how adult stem cells from bone marrow develop into differentiated ones. The work by Hebrew University researcher Dr. Assaf Zemel at the Hebrew University of Jerusalem’s Institute of Dental Sciences, together with Prof. Samuel Safran from the Weizmann Institute of Science and foreign colleagues from Germany and the US revealed an important step in understanding the mechanisms that regulate the specialization of stem cells from their undefined state.

Scientists around the world are involved in studying, describing and even manipulating the development of stem cells on their path into becoming specialized cells, such as heart, muscle, brain or any other tissue. This research has tremendous implications for the future utilization of stem cells as a new tool of medical treatment, the design of artificial tissues and the development of novel therapeutic strategies.

In an article published in Nature Physics, the team write how they have developed a theoretical model and carried out experiments on stem cells to propose a mechanism for the recently discovered sensitivity of stem cell differentiation to the rigidity of their surroundings. They described the physical changes in stem cells that are layered on supporting foundations of differing rigidities. They also showed that on a supporting matrix whose rigidity mimics that of muscle tissue, the cells become elongated and filled with aligned muscle-like fibers. This situation is fundamentally different from when the supporting substance is made either softer (to mimic brain tissue) or harder (to mimic bone tissue), in which case the cells adopt more symmetric structures and differentiate into brain and bone cells, respectively.

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