Category Archives: Life Science

Social Amoeba

At first their behavior might seem odd; to gather together in the face of starvation surely ought to end in cannibalism or death. Not so, for they are capable of an extraordinary and rare transformation. The amoebas set aside their lives as individuals and join ranks to form a new multicellular entity. Not all the amoebas will survive this cooperative venture, however. Some will sacrifice themselves to help the rest find a new life elsewhere.

These astonishing creatures are Dictyostelium discoideum, and they are a member of the slime mold family. They are also known as social amoebas. Aside from the novelty value of an organism that alternates between unicellular and multicellular existence, D. discoideum is highly useful in several areas of research. Among other things, this organism offers a stellar opportunity to study cell communication, cell differentiation, and the evolution of altruism.

In response to the cAMP distress call, up to one hundred thousand of the amoebas assemble. They first form a tower, which eventually topples over into an oblong blob about two millimeters long. The identical amoebas within this pseudoplasmodium– or slug– begin to differentiate and take on specialized roles.

Another cool example of how life has evolved novel solutions to perpetuate genes.

1,000 Species Discovered in Greater Mekong in Last Decade

Photograph of Gumprechts Green Pitviper courtesy Greater Mekong Programme/WWF International

While most species were discovered in the largely unexplored jungles and wetlands, some were first found in the most surprising places. The Laotian rock rat, for example, thought to be extinct 11 million years ago, was first encountered by scientists in a local food market, while the Siamese Peninsula pitviper was found slithering through the rafters of a restaurant in Khao Yai National Park in Thailand.

“This region is like what I read about as a child in the stories of Charles Darwin,” said Dr Thomas Ziegler, Curator at the Cologne Zoo. “It is a great feeling being in an unexplored area and to document its biodiversity for the first time… both enigmatic and beautiful,” he said.

The findings, highlighted in this report, include 519 plants, 279 fish, 88 frogs, 88 spiders, 46 lizards, 22 snakes, 15 mammals, 4 birds, 4 turtles, 2 salamanders and a toad. The region comprises the six countries through which the Mekong River flows including Cambodia, Lao PDR, Myanmar, Thailand, Vietnam and the southern Chinese province of Yunnan. It is estimated thousands of new invertebrate species were also discovered during this period, further highlighting the region’s immense biodiversity.

“It doesn’t get any better than this,” said Stuart Chapman, Director of WWF’s Greater Mekong Programme. “We thought discoveries of this scale were confined to the history books. This reaffirms the Greater Mekong’s place on the world map of conservation priorities.”

The report stresses economic development and environmental protection must go hand-in-hand to provide for livelihoods and alleviate poverty, and ensure the survival of the Greater Mekong’s astonishing array of species and natural habitats.

Full press release. I am a World Wildlife Fund member.

Bird Brain

Bird-brains smarter than your average ape

In a recent study 20 individuals from the great ape species were unable to transfer their knowledge from the trap-table and trap-tube or vice versa, despite the fact that both these puzzles work in the same way. Strikingly the crows in The University of Auckland study were able to solve the trap-table problem after their experience with the trap-tube.

“The crows appeared to solve these complex problems by identifying causal regularities,” says Professor Russell Gray of the Department of Psychology. “The crows’ success with the trap-table suggests that the crows were transferring their causal understanding to this novel problem by analogical reasoning. However, the crows didn’t understand the difference between a hole with a bottom and one without. This suggests the level of cognition here is intermediate between human-like reasoning and associative learning.”

“It was very surprising to see the crows solve the trap-table,” says PhD student Alex Taylor. “The trap table puzzle was visually different from the trap-tube in its colour, shape and material. Transfer between these two distinct problems is not predicted by theories of associative learning and is something not even the great apes have so far been able to do.”

Dolphins Using Tools to Hunt

photo of a dolphin with a sponge it uses to hunt

Photograph of dolphin with a sponge it uses to hunt, courtesy of Ewa Krzyszczyk, PLoS, high resolution.

Cool open access research from PLoS One, Why Do Dolphins Carry Sponges?

Tool use is rare in wild animals, but of widespread interest because of its relationship to animal cognition, social learning and culture. Despite such attention, quantifying the costs and benefits of tool use has been difficult, largely because if tool use occurs, all population members typically exhibit the behavior. In Shark Bay, Australia, only a subset of the bottlenose dolphin population uses marine sponges as tools, providing an opportunity to assess both proximate and ultimate costs and benefits and document patterns of transmission.

We compared sponge-carrying (sponger) females to non-sponge-carrying (non-sponger) females and show that spongers were more solitary, spent more time in deep water channel habitats, dived for longer durations, and devoted more time to foraging than non-spongers; and, even with these potential proximate costs, calving success of sponger females was not significantly different from non-spongers. We also show a clear female-bias in the ontogeny of sponging. With a solitary lifestyle, specialization, and high foraging demands, spongers used tools more than any non-human animal. We suggest that the ecological, social, and developmental mechanisms involved likely (1) help explain the high intrapopulation variation in female behaviour, (2) indicate tradeoffs (e.g., time allocation) between ecological and social factors and, (3) constrain the spread of this innovation to primarily vertical transmission.

The dolphins use the sponge to push along the ocean floor and disturb fish, that are hidden. Once the fish start swimming away the dolphin abandons the sponge and catches and eats the fish. Then the dolphin goes back and gets the sponge and continues.

How Antibiotics Kill Bacteria

Since the first antibiotics reached the pharmacy in the 1940s, researchers discovered that they target various pieces of machinery in bacterial cells, disrupting the bacteria’s ability to build new proteins, DNA, or cell wall. But these effects alone do not cause death, and a complete explanation of what actually kills bacteria after they are exposed to antibiotics has eluded scientists.
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The group found that all bactericidal antibiotics, regardless of their initial targets inside bacteria, caused E. coli to produce unstable chemicals called hydroxyl radicals. These compounds react with proteins, DNA, and lipids inside cells, causing widespread damage and rapid death for the bacteria.
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With the results of these two experiments, the researchers were able to identify three major processes implicated in gentamicin-induced cell death: protein transport, a stress response triggered by abnormal proteins in the cell membrane, and a metabolic stress response.

One Sneeze, 150 Colds for Commuters

One sneeze, 150 colds for commuters

An analysis of the germs unleashed from a single commuter’s sneeze showed that within minutes they are being passed on via escalator handrails or seats on trains and underground carriages. At the busiest stations, one sneeze not smothered by a tissue or handkerchief will provide enough germs to infect another 150 commuters.
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A single sneeze expels 100,000 droplets of germs into the air at 90mph. Individual droplets get transferred to handles, rails and other areas frequently held or touched. Up to 10 per cent of all commuters will come into contact with an area infected by that one sneeze, Dr Henderson calculated.
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Researchers asked 1,300 workers about their health and found 99 per cent of commuters suffered at least one cold last winter. In contrast, just 58 per cent of those who work from home and 88 per cent of those who walk to work regularly caught a cold last winter.

It is amazing (or maybe not but I find it amazing) how well cold viruses have evolved to have us sneeze and send out personal virus jet packs to spread them all over and let them infect others. It is sad how impolite some people are as they go around potentially infecting hundreds of other people. Partially their ignorance of basic science may also be to blame for their behavior. It is too bad others have to suffer due to their bad manners and ignorance.

Regenerating Neurons in Eyes

The retina, which is located in the back of the eye, has an outer layer of cells that detect light and translate it into electrical signals. It also has inner layers, which process the signals and send them to the brain.

In degenerative disorders like macular degeneration and retinitis pigmentosa, outer-layer cells, called photoreceptors, break down in the early stages of disease, leading to loss of vision. Extensive research has focused on replacing these cells, in an effort to restore sight. In people with advanced disease or blindness, however, the inner cell layers may also break down or become disorganized and need to be rebuilt, says Rose.

“The outer retina is like the CPU, and the inner retina is like the motherboard,” he says. “If I attach a new CPU to a dead motherboard, it won’t do any good, no matter how great a CPU it is.”
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In lower vertebrates like fish and chickens, retinal cells are known to generate new neurons in response to damage, often restoring sight. While mammals do not have the same self-healing capacity, some previous research has suggested that under particular circumstances, mammals’ retinas might be able to generate new neurons.

Do Breast Tumors go Away on Their Own?

Authors of a new study hope to begin a debate challenging the conventional wisdom about early detection of breast cancer. In an article in today’s Archives of Internal Medicine, they ask: Do breast tumors ever go away on their own?

Researchers of this controversial article note that one type of cancer found through screening — a rare childhood tumor, called neuroblastoma — sometimes disappears. In the new article, researchers try to learn if the same phenomenon occurs with invasive breast cancers found with mammograms

The Natural History of Invasive Breast Cancers Detected by Screening Mammography

Conclusions: Because the cumulative incidence among controls never reached that of the screened group, it appears that some breast cancers detected by repeated mammographic screening would not persist to be detectable by a single mammogram at the end of 6 years. This raises the possibility that the natural course of some screen-detected invasive breast cancers is to spontaneously regress.

As with so much medical research the results are not completely clear. Studies need to be followed by more studies, which often lead to more studies. As long as progress is being made this is a perfectly reasonable course of scientific inquiry. And even if progress is not being made this can be perfectly reasonable – finding answers can be hard.

Simple Webcasts on Evolution and Genes

Webcast from 23andme on human evolution. Continued: What are genes?, What are SNPs? (Single Nucleotide Polymorphisms), Where do your genes come from? and What is phenotype?. These webcasts provide an easy to understand overview. Sergey Brin, Google co-founder and husband of 23andme co-founder Anne Wojcicki. People have 23 pairs of chromosomes.

What are SNPs?:

For a variation to be considered a SNP, it must occur in at least 1% of the population. SNPs, which make up about 90% of all human genetic variation, occur every 100 to 300 bases along the 3-billion-base human genome.
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SNPs do not cause disease, but they can help determine the likelihood that someone will develop a particular illness. One of the genes associated with Alzheimer’s disease, apolipoprotein E or ApoE, is a good example of how SNPs affect disease development. ApoE contains two SNPs that result in three possible alleles for this gene: E2, E3, and E4. Each allele differs by one DNA base, and the protein product of each gene differs by one amino acid.

How Cells Age

A new study by Harvard Medical School researchers reveals that the biochemical mechanism that makes yeast grow old has a surprising parallel in mice, suggesting it may be a universal cause of aging in all organisms.
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In young organisms, SIRT1 effectively doubles as a gene-expression regulator and a DNA repairer. But when DNA damage accumulates—as it does with age—SIRT1 becomes too busy fixing broken DNA to keep the expression of hundreds of genes in check. This process is so similar to what happens in aging yeast that its discoverers believe it may represent a universal mechanism of aging.

Harvard researchers gain new insight into aging

Aging may be a case of neglect — an absentee landlord at the cellular level that allows gene activity to go awry, according to a study published today.

Scientists have long known that aging causes gene expression to change, and DNA damage to accumulate. But now, research led by Harvard Medical School scientists explains the connection between the two processes in mammals.

The paper, published in the journal Cell, found that a multi-tasking protein called SIRT1 that normally acts as guardian of the genome gets dragged away to DNA fix-it jobs. When the protein abandons its normal post to work as a genetic handyman, order unravels elsewhere in the cell. Genes that are normally under its careful watch begin to flip on.

“What this paper actually implies is that aspects of aging may be reversible,” said David Sinclair, a Harvard Medical School biologist who led the research. “It sounds crazy, but in principle it should be possible to restore the youthful set of genes, the patterns that are on and off.”

The study is just the latest to draw yet more attention to sirtuins, proteins involved in the aging process

Aging is fascinating. By and large people just accept it. We see it happen to those all around us, without exception. But what causes biological aging? It is an interesting area of research.