Syndicate content

Archive - Mar 11, 2017

Making Sense of Death-Defying Leaps by Cliff-Born Murre Chicks

Before they have the wing span to actually permit them to fly, young guillemots (also known as murres) leap hundreds of meters off towering cliffs and flutter down towards the sea, guided by their fathers. Scientists have long wondered why these tiny chicks make this remarkable leap, hoping to avoid the rocks below them, in what seems an unlikely survival strategy for a species. It had earlier been suggested that murre offspring headed off to sea once the chicks reached about one-quarter of their adult size and were large enough to defend themselves from potential predators and too large to be fed at the colony--so that this seemingly death-defying behavior could be better understood as being, in some ways, a tradeoff between the safety offered in the colony and the fast growth rates at sea, where more food is available. But after tracking the behavior of murre fathers and their offspring for six weeks in murre colonies in some of the most remote locations on the globe, in Nunavut, Greenland, and islands off Newfoundland, scientists have discovered that mortality rates were similar between chicks at sea and in the colonies. Moreover, the team, which was made up of researchers from McGill and Memorial Universities in Canada and Aarhus and Lund Universities in Denmark and Sweden, discovered that chicks at sea grew at roughly twice the speed of those at the colony, because the murre fathers no longer needed to fly back and forth to the colony to feed them. Unusually among animals, after three weeks of care by both parents, it is the father who then spends 5 to 7 weeks rearing the offspring by himself on the high seas. Meanwhile, the mother spends her time back at the colony, copulating with paramours to choose a potential suitor should her mate not return the next year. The study documented the hard work done by the father.

Castration-Resistant Prostate Cancer Cell Growth Impeded by Endostatin

Failure of hormone deprivation therapy, which is used to slow prostate cancer in patients, leads to castration-resistant prostate cancer, a lethal form of advanced disease with limited treatment options. University of Alabama at Birmingham (UAB) researchers have discovered that endostatin, a naturally occurring protein in humans, can significantly decrease proliferation of castration-resistant prostate cells in culture, and in a paper published online on January 9, 2017 in The FASEB Journal, they describe the physiological pathways and signaling evoked by endostatin. The article is titled “Endostatin Inhibits Androgen-Independent Prostate Cancer Growth by Suppressing Nuclear Receptor-Mediated Oxidative Stress." This endostatin effect is now being tested in a preclinical xenograft animal model of castration-resistant prostate cancer. "We hope we can delay the onset of castration-resistant disease," said Selvarangan Ponnazhagen, Ph.D., a UAB professor in the UAB Department of Pathology who holds an Endowed Professorship in Experimental Cancer Therapeutics at UAB. The medical treatment that deprives prostate cancer cells of androgen hormones through anti-hormone therapy creates oxidative stress in those cancer cells. This oxidative stress is associated with reactivated signaling by the androgen receptor in the cells, causing resistance to the anti-hormone therapy. The UAB researchers, led by Dr. Ponnazhagen and first author Joo Hyoung Lee, Ph.D., hypothesized that the oxidative stress might be triggered upstream of the androgen receptor, with the glucocorticoid receptor as the stress-inducer. If so, endostatin might interact with the glucocorticoid receptor to remove the oxidative stress and reduce that pro-tumorigenic function in the cancer cells, thereby preventing or delaying the onset of castration-resistant disease.

Severe Hypoglycemia Linked to Increased Risk of Death in People with Diabetes; Within Three Years of Dangerously Low Blood Sugar Episode Requiring ER Visit, One-Third of Those in Study Died

A single instance of blood sugar falling so low as to require an emergency department visit was associated with nearly double the risk of cardiovascular disease or death, according to results of a new Johns Hopkins Bloomberg School of Public Health study of older adults with type 2 diabetes. Additionally, using data from a large, longitudinal study, the researchers found that one third of the older adults with diabetes who had experienced a severe low blood sugar episode (hypoglycemia) died within three years of the incident. In analyzing their data, the researchers controlled for such variables as how severe a person's diabetes was and how long it had been since diagnosis. The researchers say that their findings suggest that doctors might want to pay special attention to patients who have been sent to the emergency department for hypoglycemia after losing consciousness, having a seizure, or experiencing another serious health event. The findings were presented on March 10, 2017 at the American Heart Association's EPI|LIFESTYLE 2017 Scientific Sessions in Portland, Oregon. The presentation was titled “"Association of Severe Hypoglycemia with Cardiovascular Disease and All-Cause Mortality in Older Adults with Diabetes: The Atherosclerosis Risk in Communities (ARIC) Study." "If you have a patient with a history of severe hypoglycemia, this could portend poorly for his or her future," says Alexandra K. Lee, MSPH, a Ph.D. candidate in epidemiology at the Bloomberg School. "Our thinking has been that you resolve a hypoglycemic episode and it's over.

Robber Fly's Aerial Hunting Skill Relies on Extreme Visual Acuity

You might expect that the miniature brains and eyes of tiny robber flies would limit their ability to launch sophisticated in-flight predatory attacks on their prey. But, according to researchers reporting in Current Biology on March 9, 2017 who've captured the rice-sized predators' tactics on film, that is not so. The open-access article is titled “A Novel Interception Strategy in a Miniature Robber Fly with Extreme Visual Acuity.” The movies show that robber flies sit and wait for a tempting prey item (or a bead) to fly past. Once they do, the flies take off using an interception strategy known as constant bearing angle (CBA), keeping their prey at a constant angle to ensure that they'll eventually meet. That's impressive, but there's more. Once the robber fly reaches a distance of about 30 centimeters from its target, it "locks on," slowing down and curving its flight path to make a successful catch even more likely. Their secret to pulling it off is all in the eyes. "We knew that these flies likely had an improved vision compared to other true flies, but we never imagined that they would give dragonflies, which are ten times larger, a run for their money with regards to spatial resolution of the retina," says Dr. Paloma Gonzalez-Bellido of the University of Cambridge. "Likewise, although we expected these flies to employ CBA, we were surprised by their use of a lock-on phase to ease the capture." The researchers, including Dr. Gonzalez-Bellido and Dr. Trevor Wardill, made their discovery by presenting flies in their natural habitats with beads ranging from about 1 to 4 millimeters in diameter on a fishing line. They recorded the flies' reaction to seeing one of those beads zoom past using two high-speed video cameras. The films allowed them to reconstruct the insects' precise flight trajectories in three dimensions.

Mayo Clinic Study Provides Critical Information on Tumor Sequencing and Chemotherapy in Breast Cancer

Tumor sequencing is increasingly used to select treatment for patients with cancer, but its role in women with newly diagnosed breast cancer is unknown. Mayo Clinic researchers reported on March 9, 2017, in the Journal of the National Cancer Institute (JNCI), the results of a prospective tumor sequencing study in women receiving chemotherapy prior to breast surgery. The article is titled “Tumor Sequencing and Patient-Derived Xenografts in the Neoadjuvant Treatment of Breast Cancer.” The goal was to determine whether tumor genomic alterations could differentiate patients with chemotherapy-sensitive and chemotherapy-resistant disease and to generate patient-derived xenografts (mouse avatars) to validate their findings. "There is great interest to use tumor sequencing data to guide therapy," says Matthew Goetz, M.D., Medical Oncologist and Co-Chair of the Breast Cancer Genome-Guided Therapy (BEAUTY) study. "However, there are limited data as to whether this approach is useful in women with newly diagnosed breast cancer who are recommended chemotherapy prior to breast surgery," he added. The main findings of the BEAUTY study, published in the JNCI, demonstrated that the most common genetic changes were not more commonly observed in chemotherapy-resistant compared to chemotherapy-sensitive tumors. However, Mayo investigators identified that an uncommon type of an aggressive breast cancer, the luminal androgen receptor subtype of triple-negative breast cancer (TNBC), was less likely to respond to chemotherapy, and was more likely to contain a unique type of mutation in p53, a tumor suppressor gene commonly mutated in TNBC.