The Purr-suit of Happiness: The Science Behind Feline Purring

As any cat person would tell you, one of the greatest joys in life is to be curled up with a feline friend as they purr. Though purring is one of the most widely recognizable and comforting sounds in the animal kingdom—a sound that has come to be virtually synonymous with coziness and contentment—the how and why behind it is still shrouded with some mystery.

Vocal Purr-duction

The scientific community defines purring as a “low-pitched regular sound produced during alternating (pulmonic) egressive and ingressive airstream”. This is a fancy way of saying that sound is continuously produced during both exhales and inhales with no interruptions in between, while keeping their mouths entirely closed. Like fuzzy little ventriloquists.

But how does purring actually work? In the 1960s, it was initially hypothesized that purring was the resulting sound of blood percolating through the inferior vena cava, the blood vessel that returns blood from the body to the heart. However, further research later disproved that theory, indicating that the purring mechanism involves communication between a neural oscillator deep in the feline brain and the larynx, or voice box. As a cat’s laryngeal muscles move, they constrict and dilate the glottis, the part of the larynx surrounding the vocal chords. During inhalation and exhalation, the air passing through the glottis vibrates, resulting in a purr.

Fun Fact: Purring isn’t limited to just domestic house cats! Several wild feline species like bobcats and mountain lions, plus their close relatives mongooses, genets and civets can all purr. But there are a number of other animals that can produce a purr that might surprise you, including rabbits, raccoons, bats, guinea pigs, gorillas and elephants!

Good Vibrations?

Though there is general consensus in the scientific community on the purring process, the question of exactly why cats purr is still up for debate, as studies regarding cat behavior and communication considerably lags behind the efforts for studying dogs. This may be partially due to the fact that dogs are typically more willing study participants (in that they are likely more easily bribed).

Though we most commonly consider a purring cat to be a contented cat, that is not always the case. It turns out that there are actually a number of other emotions and situations that will elicit purring as a response.

Cats first begin to purr when they are only a few days old. As newborn kittens are blind, deaf and overall completely helpless for the first few weeks of their lives, purring serves as a quiet, subtle form of communication and bonding mechanism between mother and offspring. Purring can help kittens communicate their location, and provides a means for mom to affirm her babies’ comfort and safety, as well as signal feeding times.

This behavior sometimes carries over into adulthood, with some cats continuing to purr while they eat or as a means to convince their human that it’s dinner time. A University of Sussex study found that cats even have a solicitous purr that they can employ for exactly this purpose. By embedding a cry similar in frequency to that of a human infant’s cry within a purr, cats can manipulate their owners into taking action and feeding them by triggering and exploiting their innate human nurturing instincts. Even the study participants with no cat experience could hear the difference in urgency between an ordinary and an “I’m hungry” purr.

Purring has also been hypothesized to be a sort of self-soothing mechanism, as cats have been observed to purr in response to nervousness, fear or stressful events, like a trip to the vet, being chased by a dog, or exploring a new environment. Cats have also been observed to purr when they are in pain and dying, leading researchers to postulate about purring’s potential healing properties—for cats and perhaps for humans as well.

Feline Fine

In the early 2000s, researchers dug further into this notion, proposing that purring may have palliative properties that may assist in accelerating the healing process for a cat’s wounds or broken bones.

Given that healers have employed the power of sound and vibrations in their work for centuries, the basis for this notion is not far-fetched. Various studies regarding sound frequencies have demonstrated promising vibratory therapy results in some animals, such as rabbits. Even NASA has explored this therapeutic avenue as a potential means to combat bone density loss and muscle atrophy in astronauts headed to space for long stints.

A 2001 study that recorded and measured the purrs of 44 felids including ocelots, servals, cheetahs, pumas and domestic cats, found that every individual in this study produced strong frequencies between 25 and 150 Hertz (Hz). They discovered that all the species except cheetahs produced frequencies at exactly 25 Hz and 50 Hz, which research suggests are the best frequencies to promote fracture healing and bone growth. Additionally, those same four felids have a strong harmonic either at or within 2 Hz of 100 Hz, a frequency that has been therapeutically used to treat wounds, dyspnea, edema and pain. These findings support the hypothesis that purring may be an advantageous, low energy mechanism that can stimulate feline muscles and bones while sedentary.

Purring releases endorphins in cats and can do the same in people. Endorphins can lower stress hormones, which is beneficial for healing, lowering blood pressure and overall stress, and helping people cope with illness.

Further studies have shown cat ownership in general has demonstrated some physical health benefits. In 2009, a 20 year study of over 4,000 people found that cat owners appeared much less likely to die of a heart attack or stroke, as opposed to people who have never known the love of a cat, with non-cat owners being 40% more likely to die of a heart attack and 30% more likely to die of another cardiovascular disease including strokes than cat owners. Another study by Australia’s Baker Medical Research Institute found that pet owners tend to have lower blood pressure than people who don’t have pets.

Though no research efforts have further explored the direct effects of using purring felines themselves as a mechanism for healing, the overall health effects cat ownership has on people is undeniable. And though the exact purpose and potential physical benefits still elude researchers, purring undoubtedly offers both a soothing psychological balm and gentle medium of communication between a cat and their people.


Making “Scents” of the Mysterious Science of Plant Odors

Corpse flower in bloom
Photo credit: “titan arum 01” by illumine23 is licensed under CC BY-NC-ND 2.0.

When it comes to plant aromas, we tend to forget that we, as humans, are not the target audience, and these odors were not designed with us in mind—we are really passive spectators to a show that luckily most of us happen to enjoy. This past spring Mother Nature demonstrated just what it means to have a target olfactory audience at Madison’s Olbrich Botanical Gardens. For the first time in about 12 years, one of the four massive titan arum (Amorphophallus titanum) plants that reside at Olbrich bloomed, an event that typically only happens for 24-48 hours at a time and 4-5 times total throughout this plant’s roughly 40 year lifespan. More informally (and aptly) known as the “corpse flower” due to its carcass-adjacent coloring and distinctly foul odor, hundreds of plant enthusiasts and hopeful spectators queued for hours to catch a glimpse and whiff of the pungent plant. Until rare events like this happen, it can be easy to forget just how interesting and complex plants really are. We romanticize and lend meaning to flowers and relish in the sweet fragrance they provide, while often completely overlooking the intricate biological and chemical processes that comprise the science of floral scent.

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Empowered Women Empower Women: Closing the Confidence Gap in STEM

Welcome back to the third and final part of our Women in Science series, where we’ve been exploring the key factors that perpetuate the gender gap in STEM. In Part 1 of this series, Breaking the Bias: Addressing the STEM Gender Gap, we dug into the key factors of gender stereotypes and male-dominated culture. Part 2, This is What a Scientist Looks Like: The Importance of Female Role Models in STEM, was all about the issue of fewer visible female role models in STEM. Last but certainly not least, this installment will focus on tackling the issue of the confidence gap, including the factors that play into it and the myriad ways we see it unfolds.

Part of my exploration of this topic included having conversations with a handful of my incredible female colleagues at Promega about the challenges women in STEM face. These colleagues were (in no particular order): Becky Godat, Instrumentation Scientist; Jacqui Mendez-Johnson, Quality Assurance Scientist; Johanna Lee, Content Lead, Marketing Services; Jen Romanin, Sr. Director, IVD Operations and Global Support Services; Kris Pearson, Director, Manufacturing & Custom Operations; Leta Steffen, Supervisor, Scientific Applications; Monica Yue, Technical Services Scientist; and Poonam Gunjal, Manager, Regional Sales.

What is the Confidence Gap?

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This is What a Scientist Looks Like: The Importance of Female Role Models in STEM

Welcome back to Part 2 of our March Women in Science series! In Part 1 of this series, Breaking the Bias: Addressing the STEM Gender Gap, we took a closer look at gender stereotypes and male-dominated culture and their roles as key factors in perpetuating the gender gap in STEM. In this installment, we will be continuing the conversation about the STEM gender gap and focusing on the key issue of fewer female role models in STEM.  

Part of my exploration of this topic included having conversations with a handful of my female colleagues at Promega about the about the challenges women in STEM face. These colleagues were (in no particular order): Monica Yue, Technical Services Scientist; Poonam Gunjal, Manager, Regional Sales; Becky Godat, Instrumentation Scientist; Leta Steffen, Supervisor, Scientific Applications; Kris Pearson, Director, Manufacturing & Custom Operations; Jacqui Mendez-Johnson, Quality Assurance Scientist; Johanna Lee, Content Lead, Marketing Services; and Jen Romanin, Sr. Director, IVD Operations and Global Support Services.

What Does A Scientist Look Like?

If someone asked you to draw a scientist, what would that person look like? Over the past 5 decades, this question has been asked of over 20,000 students across all grades from kindergarten through 12th, and evaluated in nearly 80 studies. A meta-analysis of these decades of studies revealed some interesting findings.

Between 1966 and 1977, of the 5,000 drawings collected from students during the original 11-year study, only 28 of those 5,000 drawings (less than 1% of the drawings) depicted a female scientist, with all 28 of them being drawn by girls.

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Breaking the Bias: Addressing the STEM Gender Gap

Within the broader March-long observance of Women’s History Month, March 8th marks the annual International Women’s Day. It’s a day of both celebration and reflection, dedicated not only to honoring the accomplishments and contributions that women bring to the table, but also to critical analysis of the areas where gender inequality still persists. 

Although we’ve made big strides in the last few decades, women are still significantly under-represented in many fields of science, technology, engineering and mathematics (STEM). Women make up nearly 50% of the US workforce, but less than 30% of that number are STEM workers, and with women comprising less than 30% of the world’s researchers

In honor of this year’s theme for International Women’s Day, Break the Bias, and as a woman in science myself, I was interested in exploring the challenges of anyone who identifies and lives as a woman in science, and the key factors that continue to perpetuate the gender gap in STEM fields. I invited eight of my female colleagues at Promega—diverse in roles, age, educational background, ethnicity, and experience—to sit down with me (virtually) to learn more about them and their experiences as women in STEM.

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Total Eclipse of the CAR T: How mRNA Vaccine Technology Can Be Used to Help Heal “Broken” Hearts

While you can rely on Taylor Swift and Adele to help heal emotional heartbreak, unfortunately treating a physically “broken” heart, a heart damaged by fibrosis, is a much more complicated process than putting on your favorite sad songs and wallowing in your feelings. In a recent study published in Science, researchers developed a therapeutic approach to treat damaged hearts in mice through the removal of scar tissue using genetically engineered immune cells (CAR T cells) and the mRNA technology used in the mRNA coronavirus vaccines.

Genetically engineered CAR T cells have been used l for repairing damaged hearts in mice
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Permeability Possibilities with the New NanoClick Assay

Peptide Predicament

For decades now, peptides have been a molecule of interest for drug discovery research. Peptides offer a unique opportunity for therapeutic intervention that closely mimics natural pathways, as many physiological functions utilize peptides as intrinsic signaling molecules. Macrocyclic peptides, in particular, have recently proven to be promising candidates for targeting intracellular protein–protein interactions (PPIs), an attractive but hard-to-reach therapeutic target for conventional small molecule and biological drugs.  

As with any opportunity, there are also challenges that accompany the peptide therapeutic development. Peptide ligands typically have poor membrane permeability, so thus far the majority of peptide therapeutics predominantly target extracellular proteins and receptors. There are also multiple mechanisms for cellular uptake of peptides, including both energy-dependent routes like endocytosis, and energy-independent, like passive diffusion or membrane translocation. Multiple mechanisms of cellular uptake paired with poor permeability makes engineering enough membrane permeability into peptides in order to advance them through drug discovery pipelines extremely difficult.  

There are other factors to consider in developing peptide therapeutics, such as solubility, protein/lipid binding and stability, which can also have an affect on the overall cytosolic concentration and, ultimately impact the ability of the peptide to effectively engage its desired intracellular targets.

With so many challenging factors, the ability to have a predictive, high-throughput assay to assess cell permeability, independent of the mechanism(s) of entry, would be a critical and invaluable tool to support peptide drug discovery research.

In a recent study published in ACS Chemical Biology, researchers sought to develop such a tool, and demonstrated a new application for Promega NanoBRET™ technology: the NanoClick assay.

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Awakening From Despair to Awe: 2021 International Forum on Consciousness

Banner for the International Forum on Consciousness 2021

Each year, the International Forum on Consciousness draws thought leaders from around the world to explore important, and often challenging, topics related to the exploration of consciousness. The theme for this year, Consciousness of Connection: Awakening from Despair to Awe, is an invitation to broaden curiosity about connection and take a closer look at the variety of connections that we forge in our lives.

Participants will examine the kinds of connections that transcend our individual selves and reach our inner desire to be part of an interconnected world, perhaps to transform our current sense of the individual, community, and society, from independent to interdependent. More specifically, the Forum will examine connection across the primary aspects of our lives with:

  • Self, and the many selves in our amazing neural networks
  • Others, and the multiple communities we intersect
  • Nature, and the breadth of life forms that surround us
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The Wild Genomes Program: Optimizing Conservation Outcomes Using Genomics

Although it is easy to get swept up in the dark year that was 2020, one advantage of overwhelming darkness is it makes it easier to find the bright spots, the beacons of hope, the people working to make the world a better place. One of these bright spots was the launch of Wild Genomes, a new biobanking and genome sequencing program through Revive & Restore.

Back in 2018, the Catalyst Science Fund was established by Revive & Restore with a 3-year pledge from Promega for $1 million annually. The purpose of the fund is to help support proof-of-concept projects and to advance the development of new biotechnology tools to address some of the most challenging and urgent problems in conservation that currently lack viable solutions, including genetic bottlenecks, invasive species, climate change and wildlife diseases. 

Through this fund, the Wild Genomes program was launched, with the goal of getting sequencing and biobanking tools into the hands of people working to protect biodiversity right now, and to help support them in applying genomic technologies towards their wildlife conservation efforts.

In their first request for proposals , the competitive Wild Genomes program received over 58 applications from researchers in 19 different countries, all of which aimed to address various species conservation issues using applied genomic technologies. The second round of projects, to be announced this Spring, will focus solely on marine species. Take a look at these first 11 amazing projects that have been awarded funding and the species conservation challenges they are taking on below:

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Barking Up the Right Tree: Using NanoLuc to Screen for Canine Distemper Antivirals

Canine distemper virus (CDV) is a highly contagious pathogen that is the etiological agent responsible for canine distemper (CD), a systemic disease that affects a broad spectrum of both domestic dogs and wild carnivores. While there are commercially available vaccines for CDV that can provide immunity in vivo and protect canines from contracting CD, there is a strong demand for effective canine distemper antivirals to combat outbreaks. Such drugs remain unavailable to date, largely due to the laborious, time-consuming nature of methods traditionally used for high-throughput drug screening of anti-CDV drugs in vitro. In a recent study published in Frontiers in Veterinary Science, researchers demonstrated a new tool for rapid, high-throughput screening of anti-CDV drugs: a NanoLuc® luciferase-tagged CDV.

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