The Biology Lair

Above is an electron micrograph of a cannabis sativa leaf.

Disclaimer: When conducting and even reading scientific research, it’s important to do so removed of pre-conceived social and political biases - take the science at face value.

Research on the psychoactive drug, cannabis, or marijuana, has been ablaze for some time. An article published by Robert Melamedeon the online Harm Reduction Journal draws the distinction between tobacco smoke (that contains the highly addictive compound, nicotine), and cannabis smoke (which contains the psychoactive, THC). At this point in time, it’s medically established that marijuana, even when smoked, has less severe adverse effects on the human body than tobacco. Yet the question remains - what are the degree of the detrimental effects that cannabis does have, and are there any medically beneficial effects?

Some research points to cannabis killing a variety of cancer types, including lung, breast and prostate, leukemia, lymphoma, skin, and glioma cancers. At the same time, however, a German study found that low THC doses encouraged lung cancer in in-vitro cells. Seemingly contradicting results, no? Just keep in mind that while nicotine and THC are chemically similar, their actual receptors in the human body vary in cell type distribution, which is what ultimately determines the effects on the human body.

… cannabis typically down-regulates immunologically-generated free radical production by promoting a Th2 immune cytokine profile. Furthermore, THC inhibits the enzyme necessary to activate some of the carcinogens found in smoke. In contrast, tobacco smoke increases the likelihood of carcinogenesis by overcoming normal cellular checkpoint protective mechanisms through the activity of respiratory epithelial cell nicotine receptors. Cannabinoids receptors have not been reported in respiratory epithelial cells (in skin they prevent cancer), and hence the DNA damage checkpoint mechanism should remain intact after prolonged cannabis exposure.

I highly recommend this article, which you can read fully here. It gives great insights into cell biology within a biomedical context.

Image: Courtesy of David Scharf, via The Scientist

Article: Melamede, Robert. “Cannabis and tobacco smoke are not equally carcinogenic.” Harm Reduction Journal, 2005. Web. 10 October 2012.

Pharyngeal arches are one of the four key synapomorphies of the phylum chordata, along with a post-anal muscular tail, notochord, and dorsal hollow nerve chord. Pharyngeal arches develop into the branchial arches of gills in fish, but in humans, they take a different route - five of the six develop into the bones, cartilage, and muscles in our jaws.
First Arch: “Mandibular arch;” gives rise to the mandible and maxilla, as well as the muscles of mastication and trigeminal nerve
Second Arch: “Hyoid arch;” gives rise to the hyoid bone (lesser horn) and artery, facial nerves, and muscles of facial expression
Third Arch: Stylopharyngeus muscle, hyoid (greater horn), glossopharyngeal nerve, and carotid arteries
Fourth Arch: Muscles of the soft palate, the cricothyroid muscle, thyroid and epiglottic cartilage, the vagus nerve, subclavian arteries and aortic arch.
Fifth Arch: no human structures develop
Sixth Arch: Muscles of the larynx, the recurrent laryngeal nerve, pulmonary artery, and ductus arteriosus
Photo Credit: RemakeHealth

Pharyngeal arches are one of the four key synapomorphies of the phylum chordata, along with a post-anal muscular tail, notochord, and dorsal hollow nerve chord. Pharyngeal arches develop into the branchial arches of gills in fish, but in humans, they take a different route - five of the six develop into the bones, cartilage, and muscles in our jaws.

First Arch: “Mandibular arch;” gives rise to the mandible and maxilla, as well as the muscles of mastication and trigeminal nerve
Second Arch: “Hyoid arch;” gives rise to the hyoid bone (lesser horn) and artery, facial nerves, and muscles of facial expression
Third Arch: Stylopharyngeus muscle, hyoid (greater horn), glossopharyngeal nerve, and carotid arteries
Fourth Arch: Muscles of the soft palate, the cricothyroid muscle, thyroid and epiglottic cartilage, the vagus nerve, subclavian arteries and aortic arch.
Fifth Arch: no human structures develop
Sixth Arch: Muscles of the larynx, the recurrent laryngeal nerve, pulmonary artery, and ductus arteriosus

Photo Credit: RemakeHealth

Photomicrograph of fossilized dinosaur bone cells, ca. 150 million years old (42x)
Photo Credit: Douglas Moore, via Nikon’s Small World Gallery

Photomicrograph of fossilized dinosaur bone cells, ca. 150 million years old (42x)

Photo Credit: Douglas Moore, via Nikon’s Small World Gallery

The short-tailed fruit bat Carollia perspicillata Stage 14 embryo nervous system as identified by neurofilament antibody (brown) staining. Note that the characteristic developments of vertebrate embryos are present.
Source: UNSW Embryology

The short-tailed fruit bat Carollia perspicillata Stage 14 embryo nervous system as identified by neurofilament antibody (brown) staining. Note that the characteristic developments of vertebrate embryos are present.

Source: UNSW Embryology

The above chick embryo was stained with the antibody (HNK-1) to identify the location of neural crest cells, ectodermally-derived, multipotent progenitor cells that are unique to vertebrates. These neural crest cells migrate throughout the developing embryo to give rise to different lineages of tissues.
There are four main neural crest categories:
Cranial Neural Crest - yields craniofacial mesenchyme which differentiates into cartilage, bone, cranial nerves, neuroglial, odontoblasts (cells of the teeth), and thymic cells in the cephalic region
Trunk Neural Crest - can give rise to melanocytes of the skin, the dorsal root ganglia, aortic nerve clusters, or the adrenal medulla
Vagal/Secral Neural Crest - gives rise to the parasympathetic ganglia of the digestive system
Cardiac Neural Crest - gives rise to the muscular/connective wall of main arteries

It’s important to note that the morphological complexity of vertebrates would be impossible without highly transient neural crest cells to establish entire somatic lineages throughout the body.

Photo Credit: University of Victoria Burke Lab

The above chick embryo was stained with the antibody (HNK-1) to identify the location of neural crest cells, ectodermally-derived, multipotent progenitor cells that are unique to vertebrates. These neural crest cells migrate throughout the developing embryo to give rise to different lineages of tissues.

There are four main neural crest categories:

Cranial Neural Crest - yields craniofacial mesenchyme which differentiates into cartilage, bone, cranial nerves, neuroglial, odontoblasts (cells of the teeth), and thymic cells in the cephalic region
Trunk Neural Crest - can give rise to melanocytes of the skin, the dorsal root ganglia, aortic nerve clusters, or the adrenal medulla
Vagal/Secral Neural Crest - gives rise to the parasympathetic ganglia of the digestive system
Cardiac Neural Crest - gives rise to the muscular/connective wall of main arteries

It’s important to note that the morphological complexity of vertebrates would be impossible without highly transient neural crest cells to establish entire somatic lineages throughout the body.

Photo Credit: University of Victoria Burke Lab

Oligodendrocytes and Schwann cells are two essential types of glial cells in the nervous system that are responsible for the formation of myelin sheaths around neurons’ axons. These myelin sheaths act as insulators that have provided a set of adaptations in the development of neural networks capable of transmitting rapid electrical signals.

Myelin sheaths prevent leakage of electrical signals across the cell membranes of neurons by eliminating exposure to extracellular fluid that would allow the diffusion of sodium and potassium ions necessary in generating action potentials.

Gaps in the myelin sheaths called Nodes of Ranvier allow for significantly faster signaling because the signals “jump” from node to node in a process called saltatory conduction. Signals traveling through myelinated sheaths can travel at velocities of 100 meters per second, making neural networks in complex vertebrates like humans the most advanced and efficient systems on Earth.

Image Credit (Click for Source):

Oligodendrocyte Fluorescent Microscopy

Schwann Cell and Myelin Sheath Microscopy

The genome of Monosiga brevicollis, the choanoflagellates photographed above, was recently sequenced.
Choanoflagellates,single-celled, aquatic, eukaryotic microbes are currently biological giants in unlocking the key to the evolutionary transition from unicellular to multicellular organisms, particularly in animals.
Sponges, or animals of the phylum Porifera , serve as the most primitive extant group of animals. (You can see this on this previously posted phylogenetic tree of the history of life). Interestingly enough, aquatic sponges possess flagellated feeding structures called choanocytes, which are nearly morphologically identical to the single-celled organisms we call choanoflagellates.
Photo Courtesy: National Science Foundation

The genome of Monosiga brevicollis, the choanoflagellates photographed above, was recently sequenced.

Choanoflagellates,single-celled, aquatic, eukaryotic microbes are currently biological giants in unlocking the key to the evolutionary transition from unicellular to multicellular organisms, particularly in animals.

Sponges, or animals of the phylum Porifera , serve as the most primitive extant group of animals. (You can see this on this previously posted phylogenetic tree of the history of life). Interestingly enough, aquatic sponges possess flagellated feeding structures called choanocytes, which are nearly morphologically identical to the single-celled organisms we call choanoflagellates.

Photo Courtesy: National Science Foundation

Brilliant diagram depicting the phylogenetic tree of life. Click to view the full image.

Brilliant diagram depicting the phylogenetic tree of life. Click to view the full image.

(Source: evogeneao.com)

This image depicts leukocyte macrophages (white blood cells) swarming to attack HIV virions in the brain. The inflammation caused by this process that seems be responsible for dementia in HIV patients.
Credit: Zina Deretsky, National Science Foundation

This image depicts leukocyte macrophages (white blood cells) swarming to attack HIV virions in the brain. The inflammation caused by this process that seems be responsible for dementia in HIV patients.

Credit: Zina Deretsky, National Science Foundation

(Source: nsf.gov)

Fluorescent micrograph of mouse bone cells cultured on nanofibers.
Photo Credit: Hongjun Wang, Stevens Institute of Technology

Fluorescent micrograph of mouse bone cells cultured on nanofibers.

Photo Credit: Hongjun Wang, Stevens Institute of Technology

(Source: nsf.gov)

Model for the DNA binding and cleavage fragment of yeast topoisomerase II (blue/red spheres) bound to a separated DNA strand (green spheres). One protomer is shaded darker than the other to highlight the protein’s two subunits. A second DNA (viewed end-on, yellow sticks) is modeled into a large internal hole present in the enzyme. This figure represents a likely conformational and substrate-bound intermediate of this region of the topoisomerase during its duplex DNA passage reaction.

Model for the DNA binding and cleavage fragment of yeast topoisomerase II (blue/red spheres) bound to a separated DNA strand (green spheres). One protomer is shaded darker than the other to highlight the protein’s two subunits. A second DNA (viewed end-on, yellow sticks) is modeled into a large internal hole present in the enzyme. This figure represents a likely conformational and substrate-bound intermediate of this region of the topoisomerase during its duplex DNA passage reaction.

(Source: nsf.gov)

Three-day-old embryos of red-eyed treefrog species Agalychnis callidryas. These embryos have external gills that protrude toward the surface of their eggs, where oxygen is most concentrated. This adaptation allows for high metabolic rates and accelerated development.
Credit: Karen M. Warkentin, Boston University

Three-day-old embryos of red-eyed treefrog species Agalychnis callidryas. These embryos have external gills that protrude toward the surface of their eggs, where oxygen is most concentrated. This adaptation allows for high metabolic rates and accelerated development.

Credit: Karen M. Warkentin, Boston University

(Source: nsf.gov)

Cat embryo, 4x.
Credit: James Solliday, 2007 Nikon Small World Competition Image of Distinction

Cat embryo, 4x.

Credit: James Solliday, 2007 Nikon Small World Competition Image of Distinction

(Source: nikonsmallworld.com)

This is what your tongue looks like at 40x.
The human tongue is made up of four intrinsic and four extrinsic skeletal muscles. Contrary to common belief, there is no “taste map” for the human tongue - each region can detect the common gustatory sensations (sweet, sour, bitter, salty, and umami).
Credit: Susan M. Daley, Rochester Institute of Technology

This is what your tongue looks like at 40x.

The human tongue is made up of four intrinsic and four extrinsic skeletal muscles. Contrary to common belief, there is no “taste map” for the human tongue - each region can detect the common gustatory sensations (sweet, sour, bitter, salty, and umami).

Credit: Susan M. Daley, Rochester Institute of Technology

(Source: nikonsmallworld.com)

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