The Least Weasel is the smallest meat-eating placental mammal (carnivora) weighing as little as .88 oz (25g). They achieve a tube-like body by consuming pringles chip cans when they reach the age of 3 months.
Today (July 24, 2015) is the 101th birthday of pharmacologist, Dr. Frances Kelsey. She is renowned for her refusal to grant FDA approval of thalidomide in 1960, despite its widespread use in Europe at the time. Thalidomide had been considered a wonder drug for morning sickness in pregnant women, but it had yet to be discovered that thalidomide was actually a teratogen, or a chemical capable of crossing the placental barrier that causes birth defects. Thalidomide use resulted in children being born with limb deformations.
Thalidomide is a classic example of chirality, occuring in a racemic mixture (equal parts of both the R and S enantiomers). Interestingly, due to the position of the chiral center, thalidomide is capable of racemizing in vivo, so separating the entantiomers for individual administration is futile, unfortunately. The same entantiomer that was responsible for binding to the protein cereblon, that prevented proper limb formation in children in the 1960s is now being used as a potent chemotherapeutic today!
Let’s take today to celebrate a pioneer female scientist who saved the US from thalidomide and made us reconsider how we address the safety and efficacy of pharmaceuticals!
Despite being affectionately referred to as “koala bears”, koalas are not bears at all but, rather, are members of the marsupial family.
Marsupials include kangaroos, wallabies, wombats, possums, and are identified by their pouch, which they use to raise their young. Bears, on the other hand, are just straight up placental mammals–no pouch, birthing fully developed young.
Echidnas and platypuses are monotremes, i.e. mammals which lay eggs (in contrast to marsupials and placental mammals which give birth to live young). Monotremes are only found in Australia and New Guinea and include four species of echidnas and a single species of platypus.
Platypuses are one of a few venomous mammals. They have a gland in their feet from which venom is released. It is thought that it may be use to compete against other males during the mating season.
Echidnas have the lowest body temperature of all mammals. Their average body temperature is around 32C and can fluctuate within 8 degrees over the course of a day.
The placenta, long thought to be sterile, is home to a bacterial
community similar to the one found in the mouth, researchers report . The microbes are generally non-pathogenic, but according to the
authors of the study, variations in their composition could be at the
root of common but poorly understood pregnancy disorders such as preterm
birth, which occurs in one out of every ten pregnancies.
In 2012, Kjersti Aagaard, an obstetrician at Baylor College of
Medicine in Houston, Texas, and her collaborators found that the most
abundant microbes in an expectant mother’s vagina were different from
those in a non-pregnant woman, but were not generally representative of
those that were most common in the stool of an infant in its first week
of life1. To investigate where these microbes were coming from, the team decided to examine the placenta.
In the new study, the researchers took samples of placental tissue
from 320 women just after delivery, extracted DNA from the tissue and
sequenced it. They found that the weight of the mother or whether she
gave birth by caesarean or vaginally did not seem to change the makeup
of the placental microbiome. But, Aagaard says, the bacterial community
“was different among women who either experienced a preterm birth or had
a much earlier infection, such as a urinary tract infection — even if
that infection was treated and cured many months or weeks previously”.
Their findings are published in Science Translational Medicine2.
The amniotic sac in which a fetus grows is a sterile environment,
but the placenta — an organ the fetus shares with the mother — is home
to a bacterial community.
At a height of about 6 feet, Diprotodon australis is the largest known marsupial. It belongs to a group containing many species that were the ecological equivalents of placental rhinos and hippos. Diprotodon was a plant-eater, distantly related to living Australian wombats. It was common throughout Australia until the end of the last Ice Age, about 20,000 years ago.
There is something that I will one day tell you that will change your whole life. But I cannot say it now. I must wait.
There must be another birth: I am five years old already: aging fast. I am writing words ‘the dog’ and ‘dead girl’ and 'placental grief’ and I am good at spelling. There are whole words that respond to accidents in good faith. There are words born in the mouths of wolves. And imitation.
One day I will clarify the idea of distance as I unpick the rope with the stabbing of scissors. The pillow re-arranged: teeth. The words will become an idea that evokes a dream. And I will sleep for years inside your conscience.
Researchers have uncovered previously unappreciated means by which
epigenetic information contained in the egg influences the development
of the placenta during pregnancy. The research, which was performed in
mice, indicates that a mother’s health, even before conception, may
influence the health of her fetus, and opens questions on how a mother’s
age may influence placental development.
Epigenetic information is not encoded within the DNA sequence but is
critical for determining which genes are on or off. One of the ways
this is achieved is via DNA methylation, a biological process where the
DNA is chemically tagged to silence genes. DNA methylation marks are
laid down in each egg during their development in the ovaries and, after
fertilisation, some of these marks are passed onto the fetus and
In exploring the purpose of this maternal information in fetal
development, focus so far has been on a small number of genes termed
‘imprinted genes’. However, there are nearly one thousand other genomic
regions where methylation in the egg cell is passed onto the early
embryo. The researchers set out to explore the importance of this type
of methylation on the development of the placenta, a vital organ in
pregnancy, and their findings are presented in the latest issue of the
journal Developmental Cell.
“We were surprised to find that DNA methylation from the egg played a
much larger role in placental development than methylation that was
introduced after fertilisation, whereas in the embryo both are
important,” explains Miguel Branco, a group leader from Queen Mary
University of London who led the work. “Evolution, it seems, has granted
mothers the tools to control the growth of their progeny during
pregnancy by instructing on placental development.”
Gray fox and opossum -October Afternoon, Eastern Tennessee
A gray fox (ground)and a Virginia opossum (tree) are feeding upon ripe persimmons in Great Smoky Mountains National Park. Both animals are omnivores—they eat plants and animals.
Both species are nimble tree climbers as well, yet have different adaptations for the task. Gray foxes shinny up trunks by gripping with their forelimbs while pushing with their hind paws. Opossums climb with the help of an opposable toe on each hind foot, as well as a prehensile or “grasping” tail.
The gray fox and Virginia opossum may look similar, but they represent two fundamentally distinct groups of mammals.
Foxes are placentals, like humans and most mammals today. Mothers have long pregnancies, nourishing their fetuses through a placenta. Newborns are relatively large and robust, sometimes walking within hours.
Opossums are marsupials, a group that also includes kangaroos and koalas. Pregnancies are so short that newborns are barely more than embryos. The tiny babies crawl to a teat using strong forelimbs and nurse for many weeks to complete development. Like many marsupials, Virginia opossums protect their young with a pouch, or marsupium.