Circadian Release of HSCs

Last month, Méndez-Ferrer S et al. published an article on Nature, exploring the circadian pattern of haematopoietic stem cell release.

First, by applying continuous light, continuous dark, and jet-lag environmental cue, the authors showed a regularly circadian pattern of haematopoietic stem cells release, through analyzing colony-forming units in culture (CFU-C) and LSK cells (lineage-negative Sca-1 + c-Kit +) from blood. The peak reaches at 5 hour of Zeitgeber time, and nadir lies 17 hour of Zeitgeber time (5 hours after the start point of darkness). This rhythmic oscillation is maintained in total darkness, gets a shift during jet lag, and becomes arrhythmic in continuous light.

Stemming from that Cxcl12 (SDF-1, stromal cell-derived factor-1) is the only known chmokine capable of directed migration of HSCs, they further investigated the impact on Cxcl2 of bone marrow cells in both protein and mRNA expression by manupilating the circadian cycle. The results obeyed the circadian oscillations. But Cxcl12 flatuations mirrored that of HSCs both in protein and mRNA level, which is consistent with current proposed model.

In advance, the authors digged into the relationship between sympathetic nervous system (SNS) and the circadian pattern of HSCs release, plus Cxcl12 expression. Employing the neurochemical sympathectomy approach with 6-hydroxydopamine (6OHDA), the circadian pattern of HSCs by CFU-Cs was abolished. The authors then did surgical sympathectomy by unilateral microsection of both sciatic and femoral nerves. Compared with the sham-operated side, the circadian pattern of Cxcl2 is detroyed in the denervated side.
Moreover, the authors discerned that this Cxcl12 circadian effect is mediated by β3 adrenergic receptors pharmacologically, with series of in vitro bone marrow stromal cells (MS-5) treated by a variety of adrenergic agonists or antagonists.

This is a very decent paper dissecting the circadian oscillation and release of HSC and Cxcl12 expression. However, this raise a question mark in my mind. First, is adrenaline secreted circadianly? To my knowledge, adrenaline from ANS (autonomic nerve system), or any catecholamine, is not secreted in a circadian pattern. They are usually episodic, elevated when needed such as coping stress. What I can think of most, is that ACTH (adrenocorticotropic hormone) is circadian, driving corticosteroid and minerosteroid to be circadian, and may partly act on medulla and contribute adrenaline from adrenal glands to total adrenaline.

Second, neither sciatic nor femoral nerves is pure sympathetic nerve. Denervation of sciatic and femoral nerves will cause far more downstream physiological effects than just sympathectomy. Denervation itself and subsequent biological changes would be a big topic to be explored. I would challenge this model as an evidence to illustrate adrenaline's role on Cxcl12 expression.

Despite the above-mentioned questioning, it is very important to know that release of HSCs is circadian. I believe that such the finding will benefit medicine in application for either chemotherapy or transplantation.

CrispAds Blog Ads


Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Medicine, Biomedical Science, Biological Science, Medical Science, Biological Science, Medicine-Haematology, Medicine-Oncology, Medicine-Transplantation, Medicine-Immunology, Medicine-Molecular Biology, Medicine-Molecular Medicine, Medicine-Cell Biology, Medicine-Developmental Biology, Circadian cycle, HSC, HSCs, Haematopoietic stem cell, Jet-lag, Environmental cue, LSK cells, lin - Sca-1 + c-Kit +, Zeitgeber, CXCL12, Cxcl12, chemokines, Cytokines, bone marrow, SNS, sympathetic nerve system, sympathectomy, 6OHDA, 6-hydroxydopamine, sciatic nerve, femoral nerve, tibia denervation, adrenergic receptor, Medicine-Pharmacology, bone marrow stromal cells, MS-5, ANS, autonomic nerve system, catecholamine, ACTH, adrenocorticotropin, corticosteroid, minerosteroid, medulla, adrenal gland, Medicine-Endocrinology, Denervation, Medicine-Neurology, chemotherapy, Medicine-Cancer Biology, adrenaline

Update of Free Museum Admissions Provided by Bank of America

As my last post in regard to Bank of America's promotion, here comes the details.

The unexpected change compared to that of last year is, in contrast to one cardholder can get two tickets at the booth last year, this time the free admission is limited to cardholder only. In other words, friends, or children who do not have Bank of America card will need to pay. Thus the event this year, although still a feast to reward their old customers, is more a campaign to drive more people to create financial relationships with them.

As to the participating museums, it has dropped from 95 to 70. Some big famous museums are no longer on the list, but the good side is they spread out to more cities and more states.

I should say, despite the down sides, this is still a decent deal - the first weekend for every month, and last for one full year! So, get it ready with your Bank of America ATM or Debit or Credit Card (disclaimer: Wilfred Wu Wonderland is not affiliated with Bank of America, her holding company[ies], or her subsidiary[ies]), and remember to bring your photo ID. Line up and get a free ticket to enjoy a mindful of arts or science, with no extra charges.

Their official disclosure webpage: http://www.bankofamerica.com/museums

Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Free!, Museum, Admission, Admissions, Museum Admission, Museum Admissions, Free Museum Admission, Free Museum Admissions, Bank of America, Bank of America customers, Cardholder, ATM card, Debit card, Credit card

Is Warburg Effect Determined by Embryonic Isoform of Pyruvate Kinase?

It has been more than 75 years since Dr. Otto Warburg disclosed the aerobic glycolysis in tumor cells around 1930. This metabolic phenomenon in tumors, seperating it from Kreb's cycle and anerobic fermentation, features high rates of glucose uptake, but low rates of oxidative phosphorylation, with production of lactic acid even in the presense of oxygen. The principles of aerobic glycolysis has been applied to fancy, popular approach to detect cancer recurrence sucha as PET (Positron Emission Tomography) in nuclear medicine contemporarily. Yet there are more to be explored, and potentially there may be more to be exploited in cancer treatment or prevention.

Christofk HR et al. published a paper on Nature last month which likns Warburg's observation to embryonic isoform of pyruvate kinase, M2. It has been known that cancer cells express embryonic M2 isoform of pyruvate kinase exclusively.

The authros first verified this exclusive expression of M2 isoform in cancer tissue by immunoblotting and immunohistochemistry. Then, using short hairpin RNA (shRNA) knockdown in H1299 cells (a human lung cancer cell line), plus rescue by mouse PKM1 (pyruvate kinase M1 isoform) and PKM2 (pyruvate kinase M2 isoform), they revealed that M2 isoform rescues more, in terms of glycolytic rate and replication. Moreover, M2 cells are mroe resistant to hypoxic circumstances, and mitochondrial ATP synthase inhibitor, oligomycin. Even more, ocygen consumption is lower in cells bearing M2 compensation, and lactate production is significantly higer. These findings succesfully connect M2 isoform of pyruvate kinase to Walburg's aerobic glycolysis as a determinant to escape tricarboxylic acid cycle and to enter the pathway for lactate production.

In the meantime, the authors also employed xenograft study on nude mouse by injecting H1299 tumor cells with M1 or M2 expression. This in vivo model resulted in bigger tumor, and more probablity to form tumors by lung cancer cell line bearing mouse M2 isoform vector.

I should say this is not intuitive, or even a violation of my current knowledge of biochemistry and glucose metabolism. Shouldn't the determining factors for entering citric cycle or lactic acid production lie after pyruvate? Are the end product of pyruvate by different isoform of pyruvate kinase different? Or, does pyruvate kinase act after pyruvate formation, and drive them into distinct destiny according to specific isoform? Or, doses the conformation of pyruvate kinase give it the ability to intervene the downstream reaction? (More spatial and temporal questions to be asked)

If we put aside these questions to clarify and make things consistent and focus on the applications, we may also ask how do cells switch from the adult M1 isoform of pyruvate kinase back to embronic M2 isoform? It is known that M2 isoform is a splice variant of M1, and how do we control than?

Although my questions may sound absurd, but I do take the authors' findings very seriously as an important breakthrough in cancer biology with great potential to further study, cancer treatment, and prevention.



Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]

Tags: Medicine, Medicine-Oncology, Medicine-Cancer Biology, Medicine-Biochemistry, Medicine-Nuclear Medicine, Medicine-Biomedical Science, Medicine-Biological Science, Medicine-Bioscience, Dr. Otto Warburg, glycolysis, Aerobic glycolysis, citric cycle, citrate cycle, Kerb's cycle, TCA cycle, Tricarboxylic acid cycle, Anaerobic fermentation, Anaerobic glycolysis, Lactate cycle, Pyruvate, Pyruvate Kinase, Glucose metabolism, Cancer Cell metabolism, Pyruvate Kinase, M2 isoform, Embryonic isoform, Medicine-Developmental Biology, M1 isoform, Adult isoform, Immunoblotting, Immunohistochemistry, shRNA knockdown, hypoxia, mitochondrial ATP synthase, nude mouse, xenograft study, conformation change

Bank of America to Offer Free Museum Admissions, Again!

If you remember my post last year regarding the free admissions to museums provided by Bank of America, it is back again!

Although the detail has not been disclosed officially, but preliminarily there will be free museum admissions for Bank of America customers in 2008. Unlike the one in 2007, which confined the activity throughout but only in May, it is said the free admissions will be granted for the first weekend for several months.

So far we don't know exactly which museum is on the list or which is not. But I love you soooooo much, Bank of America! I am looking forward to the these coming events!

CrispAds Blog Ads


Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Free!, Museum, Admission, Admissions, Museum Admission, Museum Admissions, Free Museum Admission, Free Museum Admissions, Bank of America, Bank of America customers, Cardholder

Another Example of Immune System Getting Involved in Development - Neurodegenerative diseases may be regarded as autoimmune diseases

In addition to my last post in November, 2007, Beth Stevens et al. published a paper on Cell that adds another example of immune system involved in development, also in central nervous system (CNS).

Inspired by the coincidence of dynamic synaptic refinement with appearance of astrocytes in the postnatal brain, and recent evidence indicating a role for astrocyte-derived signals in synapse development, the authors used gene profiling approach to screen candidate retinal ganglion cells (RGCs) genes that are upregulated by astrocytes. RT-PCR confirmed this finding. And further histology studies also verified that C1q is localized to developing CNS synapse in vivo throughout inner plexiform layer (IPL), retinal ganglion cells (RGCs), distal lateral geniculate nucleus (dLGNs). C1q "tag" unwanted CNS synapses as they opsonize pathogen or antibody, pruning of inappropriate synapses. Further, C1q-deficient (C1qKO) mice have defects in this developement shift of synaptic convergence. Without synapse elimination, LGN neurons remain multiply innervated by RGC axons, and they are defective in eye-specific segregation.

On the other hand, they also revealed that the expression of C1q declines as the nervous system mature. These neuronal C1q are downregulated in adult. However, they "revive" again in a mouse model of glaucoma! Their observation showed that C1q overexpress at early stage of glaucoma, prior to overt neurodegeneration.

This paper underscores the role that the immune system may act against "self" in a normal, physiological way in development. Moreover, it highlights hazardous effect when this immune response went too far, shedding a light on that neurodegenerative diseases may be taken as autoimmune diseases. There are quite a lot questions to be asked. In terms of neurology and neurosciene, can this model be broadened from retina and geniculate nucleus to cortex, midbrain or other part of CNS? Are C1q and complement cascade the mechanism how we forget, and how we reshape our memory? Are they also involved in other neurodegenerative disease, say Alzheimer or Parkinsonism? In terms of rheumatology and immunology, are there any other members of immune system participating in this process other than complement system? Although it has been known that steroid can cause glaucoma, but could we treat it, and other neurodegenerative diseases, from the perspective of autoimmune diseases?

Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Medicine, Medical Science, Biomedical Science, Biological Science, Bioscience, Medicine-Immunology, Medicine-Rheumatology, Medicine-Neurology, Medicine-Neuroscience, Medicine-Developmental Biology, CNS, Central Nervous System, Medicine-Developmental Biology-Synapse Convergence, Synapse refinement, Synapse elimination, Astrocyte, Medicine-Rheumatology-Autoimmune disease, Medicine-Neurology-Neurodegenerative Disease, Medicine-Immunology-Complement Cascade, C1q, C1qA, C1qB, C1qC, Astrocyte, Glia cells, RGC, RGCs, Retinal ganglion cells, gene profiling, RT-PCR, IPL, inner plexiform layer, LGN, LGNs, Lateral geneiculate nucleus, Medicine-Ophthalmology-Glaucoma, Medicine-Ophthalmmology, Cortex, Midbrain, Memory, Alzheimer, Parkinsonism, Glucocorticoid, Steroid

Prostatic acidic phosphatase (PAP) Enhances HIV Infection

CrispAds Blog Ads


Münch J et al. published a paper regarding how semen can promote the HIV (human immunodeficiency virus) infection on Cell last December. Inspired by the idea that screening of peptide libraries from human body fluids is a useful approach to discover unknown molecules modulating HIV-1 infection, they turned their attention to semen, an indispensible factor in all STDs (Sexually Transmitted Diseases).

Pooling 183 ml of human semen, they purified and obtained fractions by cation-exchange separation, followed by reversed-phase (RP) chromatography. Then each fraction was tested for respective infectivity for HIV-1 by mixing each fraction with HIV virons to infect engineered cell lines expressed CD4 / CXCR4 / CCR5. They found a fraction, which was then further recognized as a segment of PAP (prostatic acidic phosphatase) by mass spectrometry (MS), significantly increase infectivity of HIV.

They found these PAP fragment are active for HIV infection only after the solutions turned turbid either spontaneously or after agitation. Thioflavin T, Congo red staining, X-ray powder diffraction, and even electron microscopy finally clarified that these PAP fragment formed amyloid fibrils. These fibrils, termed SEVI (Semen-derived Enhancer of Virus Infection), was postulated to capture HIV virons, promote viral attachment to the target cell, and hence facilitate viron fusion, with the support of p24 binding assay and direct visualization by microscope or electron microscope.

The paper further revealed that SEVI is a general enhancer of HIV-1 infection, independent of viral genotype or phenotype, and cell type.

This is a decent paper unveiling the role of semen in HIV transmission. On the other hand, instead of exposing semen directly to cells expressing CD4 / CXCR4 / CCR5, I am more curious what role does semen play in getting HIV virons breaking through vaginal mucosal cells. After all, this is the place where body fluids meet in coital acts, and true infection of T cells or dendritic cells can only happen after that.

Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Medicine-Microbiology, Medicine-Immunology, Medicine-Infectious Disease, Medicine-Urology, Medicine-Biochemistry, Medicine-Urology-Prostate, Medicine-Urology-STDs, Medicine-Infectious Diseases-STDs, HIV, Human Immunodeficiency virus, Medicine-Proteometrics, Semen, Seminal fluid, HIV-1, Body fluids, Sexually Transmitted Diseases, Chromatography, CD4, CXCR4, CCR5, PAP, Prostatic acidic phosphatase, mass mass spectrometry, Thioflavin T, Congo red, X-ray powder diffration, electron microscopy, amyloid fibrils, beta sheet, SEVI, Semen-derived Enhancer of Virus Infection, p24 binding assay, vaginal mucosal barrier, Medicine, Medicine-Biomedical science, Medicine-Biological Science

GABA beyond the Nervous System!

A paper by And鄚g M et al. drew my attention, idicating that GABA (gamma-aminobutyric acid) and GABA receptors also play important roles outside the central nervous system.

Published on Nature last month, the authors showed the impact of GABA upon cell proliferation and cell cycle regulation by the following three models: (1) embryonic stem cells, (2) blastocyst cells, (3) neural crest stem cells (NCS). Starting with expression analysis of these cells for GABA receptors, in addition with electrophysiologic studies, they showed hyperpolarization of the cells upon activation of GABAA receptors by GABA agonist. Then, with pharmacological approaches, they observed that the colonies are smaller, there are fewer cells, and more cells stayed in S stage of cell cycle, when GABAA agonist is given. And it is verified by reversing the effect with GABAA antagonist. Genetically, knocking down GABAA receptor also reverses this negative proliferation effect of GABA.

Digging into the molecular level further, the authors revealed that this regulation by GABA and GABAA receptor is dependent on PIKK (phosphatidylinositol-3-OH kinase-related kinase) family of kinases, including ATM (ataxia telangiectasia mutated), ATR (ataxia telangiectasia Rad3-related), and DNA-PK (DNA protein kinase). It is also contigent on H2AX (Histone H2A). The authors provided evidences of both pharmacological inhibition and genetical knock-down by RNAi.

Therefore, here is the proposed model: GABA or other GABA agonist activate GABAA receptor, inducinghyperpolarization of these stem cells. Subsequently, it signals through PIKK family such as ATM/ATR/DNA-PK, and histone variant H2AX. These S-phase checkpoint kinases thus block the cell cycle at S phase, resulting in sharp decrease of cell proliferation, and an attenuation of progenies in this stem cell niche.

The findings denote a fundamentally different mechanism of proliferation control of stem cells compared to somatic cells. What impressed me more is that, although shown upstreamingly rather than other terminal-differentiated cells, GABA has her role outside the nervous system. Here we see its importance in early development of an organism.


Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: GABA, gamma-aminobutyric acid, CNS, Central Nervous System, GABA receptor, GABAA receptor, GABA-A receptor, Cl-, Chloride channel, cell proliferation, Med-Neurology, Med-Neuroscience, Developmental Biology, Med-Developmental Biology, ESC, Embryonic Stem Cell, Blastocyst, NCS, Neural Crest Stem Cells, Electrophysiological studies, patch-clamp technique, Med-Cell Biology, Med-Molecular Biology, Med-Pharmacology, Med-Genetics, siRNA, Knock-down, PIKK, phosphatidylinositol-3-OH kinase-related kinase, ATM, ataxia telangiectasia mutated, ATR, ataxia telangiectasia Rad3-related, DNA-PK, DNA protein kinase, H2AX, Histone H2A, Cell cycle, S phase, checkpoint, BrdU staining, 5-bromo-2-deoxyuridine, PI, Propidium iodide

"Dystrophy" - A Mechanism How Tregs Lead Effector T cells to Apoptosis

CD4+ CD25+ Foxp3+ regulatory T cells (Tregs) have been well known to regulate immune responses, including suppress effector CD4+ T cells. However, the molecular mechanisms underlie this process is in debate. Pandiyan P. et al. revealed an inetersting perspective on Nature Immunology, which I interpret it as "dystrophy".

First, the authors reconfirmed that Treg cells induce effector T cells apoptosis, in a time-dependent manner, by in vitro assay with coculuture of Tregs and effector T cells.

Further, they showed that additions of cytokines that signal through the common gamma chain, will rescue, though in different degree, this apoptosis effect. Among these the IL-2 (Interleukin 2) has the greatest effect. On the other hand, the authors uncovered that the supernatant of Tregs cocultured with effector Tcells has much less IL-2 concentration than control. They further proved that it was due to Tregs imbibed far more IL-2 than than naive control T cell did, whereas IL-2 expression by effector T cells remained constant at mRNA and protein level in both circumstances.

Before the effector T cells are killed, they had less expression of cytokine receptors CD25 and CD132, indicating impaired positive feedback loop by IL-2.

Meanwhile, the authors also revealed that Bim-deficient effector T cells were completely protected from apoptosis caused by Tregs. Overexpressing Bcl-2 also protected them. These echoes the findings that Bcl-2 inhibit cytokine deprivation-induced apoptosis, and Bim promotes it.

Using scid mice modeled for inflammatory bowel disease, the authors provided more evidences of apoptosis associated with Tregs, although I didn't see they further clarify the point of cytokine deprivation-mediated apoptosis by this approach.

In conclusion, this is an intriguing paper broaching a concept of "nutrition and malnutrition" in cellular level. Short in IL-2, the dystrophic effector T cells finally go apoptosis, which maintain the immune system in a balanced and homeostatic status.
CrispAds Blog Ads

Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Dystrophy, Regulatory T cell, Treg, Effector T cell, Apoptosis, Survival, CD4+CD25+Foxp3+ Treg, CD4+ T cells, cytokine, common gamma chain, Interleukin, IL-2, IL-2 receptor, cytokine receptor, CD25, CD132, mRNA expression, protein, Bcl-2 family, Bim, Bcl-2, scid mice, IBD, inflammatory bowel disease, nutrition, malnutrition, immune system, autoimmune disease, Medicine-Immunology, Medicine-Molecular Biology, Medicine-Gastroenterology, Medicine-Rheumatology

Cross Validation in Human and Animal Model for Germinal Matrix Hemorrhage

There is an interesting paper published by Ballabh et al. on Nature Medicine regarding germinal matrix hemorrhage, one of major pathologies in premature infants that may lead to cerebral palsy, hydrocephalus, and mental retardation.

Starting with gross and microsopic observation of highly vascularization in germinal matrix by neuroanatomy approach, the authors hypothesize the role of VEGF (vascular endothelial growth factor) in the development of germinal matrix.

By autopsy of human infants suffered from premature death or spontaneous abortion, the authors revealed that VEGF, angiopoietin-2, and endothelial proliferation index, are highly increased in germinal matrix, compared to those in the white matter analagen, or cortical mantle. These histological, biological and genetic findings are then validated in rabbit pups, who were delivered pretermly by cesarean section.

Then the authors further extended the experiments for pharmacology with this rabbit model, whose gestational period is around 31 days. Prenatal treatment with COX-2 inhibitor celecoxib decreased VEGF level, decreased angiopoietin-2 level, decreased germinal matrix enthelial proliferation, and substantially decreased the incidence of germinal matrix hemorrhage. On the other hand, prenatal VEGFR2 inhibitor ZD6474 (vandetanib) treatment also reduced the incidence of germinal matrix hemorrhage.

This is a very interesting paper. First, the experiment design successfully cross validated a disease between human and an animal model. Second, employing the validated animal model, the authors soon bridged the pathogenesis and the treatment solutions together. Third, for selection of angiogenic inhibitors, they not only test ZD6474 as most people would do so intuitively, but also celecoxib, a popular, commonly-seen, and well-developed FDA-labelled drug that clinical trial may be at hand.



Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Medicine, Medicine-Medical Science, Medicine-Biological Science, Medicine-Translational study, Medicine-Translational Biology, Medicine-Biomedical Science, Medicine-Clinical Study, Medicine-Clinical Trial, GMH, Germinal Matrix Hemorrhage, Preterm, Prematurity, Cerebral palsy, Hydrocephalus, Mental retardation, Gross pathology, Microscopic pathology, Medicine-Neurology, Medicine-Obstetrics, Medicine-OBGYN, Medicine-Pediatrics, Medicine-Neuroanatomy, Medicine-Anatomy, Medicine-Pathology, Medicine-Developmental Biology, VEGF, Vascular endothelial growth factor, Autopsy, Spontaneous abortion, angiopoietin, angiopoietin-2, endothelial proliferation index, white matter analagen, cortical mantle, Medicine-Histology, Medicine-Biochemistry, Medicine-Genetics, Rabbit, animal model, Cesarean section, Medicine-Pharmacology, COX-2 inhibitor, Cyclooxygenase-2 inhibitor, celecoxib, Celebrex, ZD6474, vandetanib, VEGFR2 inhibitor, Zactima, Pathogenesis, FDA, Food and Drug Administration

Entosis - Is it involved in intrinsic tumor suppression, and ductular/tubular structure development?

Overholtzer M. et al. published a paper on Cell, describing a "cell eats cell" phenomenon, which they named it "Entosis". In contrast to anoikis, this is a non-apoptotic cell clearance mechanisms, characterized by cell-in-cell invasion.

The authors first observed this cellular behavior in tracking the fate of MCF10A cells (human mammary epithelial cells) in suspension cultures. After detachment, they noticed that some of these human mammary epithelial cells are internalized into their neighbor cells. Investigating cells lost of attachement in other cell lines, including ovarian epithelial cells, mesothelial cells, human umbilical vein endothelium cells, human embryonic kidney cells, and other mammary carcinoma cells, showed similar pictures, but the interalization rate varies. This is a whole new process never found in cell biology before, thus they termed it "entosis".

Further studies of entosis revealed that it is independent of those apoptotic processes that can be seen in anoikis. Although loss of attachment is the premise of entosis, cell-cell adhesion is required. Adherens junctions and cadherins and are indispensible for it. The engulfment-internalization requires actin, myosin II, Rho, and ROCK (downstream effectors of Rho signaling) activity. After entosis, the destiny of entraped cell can be either dead, or can be released! How does the engulfed cell be killed? The authors pointed it to lysosomal enzymes degradation.

This "cell eats cell" picture, or from another point of view, "a cell invades into another cell", as the author mentioned, underlies the frequently-seen "cell-in-cell" or "cannibalism" features in pathology or cytology. They also proposed that this may represent an intrinsic tumor suppression mechanism for cells detached from extracellular matrix.

The paper actually begets many questions to be asked in a variety of dimensions. Since the inward growth of the mucosal cells in a ductular or tubular structure is similar to detachement to the basement membrane or extracellular matrix, I am most curious if newly-discovered process involves in the development of hollow lumen in those ductular or tublar tissue.

Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Entosis, Medicine-Cell Biology, Tumor, Cancer, Development, Duct development, Tubule development, Anoikis, Apoptosis, Non-apoptotic, breast cancer, mammary cell carcinoma, suspension cultures, cell cultures, extracellular matrix, ECM, basement membrane, ovarian epithelial cells, mesothelial cells, umbilical vein endothelial cells, embryonic kidney cells, actin, myosin, Rho, ROCK, cadherin, adherens junction, lysosome, lysosomal enzyme, cell-in-cell, cannibalism, Pathology, Cytology, Medicine-Pathology, Medicine-cytology, Medicine-Developmental Biology, Medicine-Molecular Biology, Medicine-Biomedical Science, Medicine-Medial Science, Medicine-Biological Science

Vision, Light, and Circadian Clock

CrispAds Blog Ads

Since my last post regarding the paper that studied the sleep of the zebrafish, I was keep thinking of the role of light and photoreceptor in our physiological control. There is a paper in Cell focusing on circadian clock, retina, and vision processing.

Storch K-F et al. first confirmed the intrinsic circadian clock of retina, by whole-genome microarray obtained from whole eyes, with the scenario of constant darkness, or 12:12 hr light-dark cycle.

Then using mice lacking Bmal1, either retina-specific or in all tissue, the authors showed that the gene expression rhythm was wildly disturbed, even the light-dark interval was given. This underscored the autonomy of the local intrinsic circadian clock within the eyes.

On the histology aspect, however, the retinas of these mice with either globally or locally targeted Bmal1 gene, appeared structurally normal by light microscopy, and further by electron microscopy.

The authors then turned to electrophysiological studies. Employing electroretinogram (ERG), they found both the Bmal1-deleted mice manifested defective inner retinal electrical responses to light, but the photoreceptor response was normal. This virtually suggests that the intrinsic circadian clock of the retina may be involved in vision processing.

Back to my original question, do zebrafish have intrinsic clock in her eyes? Or it is overwhelmed by the light?

Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]
Tags: Circadian Clock, Circadian rhythm, Vision, Environment, Developmental Biology, Neurology, Ophthalmology, Molecular Biology, Physiology, Electrophysiology, Histology, Whole Genome Microarray, Bioinformatics, ERG, Retina, Medicine, Medical Science, Biomedical Science, Biological Science, Medicine-Ophtalmology, Medicine-Neurology, Medicine-Developmental Biology, Medicine-Molecular Biology, Medicine-Genetics

How does zebrafish sleeep?

Zebrafish is one of the most important model organisms in biomedical research, and there is an interesting paper on PLoS Biology studying the sleep of zebrafish.

Yokogawa T. et al. used adult fish sleep recording system (AFSRS), a device videotracking fish illuminated by an infrared source under light and dark conditions, to conduct the behavioral studies. They confirmed that, as in humans, zebrafish sleeps, with the characteristics of reversible periods of immobility, increased arousal threshold, and place preference. Similar to the homeostatic regulation in mammals, rest deprivation, by electrical stimulation, is followed by a sleep rebound, but mostly in the dark. However, rest deprivation by the light does not get obvious sleep rebound afterwards. In fact, light supresses sleep in zebrafish, which is very different from human and mammals, but close to birds.

On the molecular aspect, the authors studied hypocretin receptor and hypocretin, the only neurochemical system known to be involved in narcolepsy, a clear human sleep disorder. Using in situ hybridization, they showed that hypocretin receptor (hcrtr) is widely expressed in the brain of zebrafish embryos and adults. However, histologically, her hypocretin receptor does not colocalize with major monoaminergic cell groups in zebrafish embryos and adults. Neither does it colocalized with cholinergic cell groups. In contrast, it colocalizes with large populations of GABAergic neurons, including a subpopulation of Adra2a-positive GABAergic cells in the anterior hypothalamic area, where nervous system meets endocrine system.

Then they went zebrafish with mutation of hypocretin receptor. These fish lacks hypocretin receptor, and behaves disparately: sleep amounts were decreased by 20% - 30% during the night, 60%-70% increase in the number of sleep-wake transitions, 60% decrease in sleep bout length during the night. In short, hcrtr null mutant fish has short and fragmented sleep.

The authors further employed pharmalogical approaches by intracerebralventricular injection of hypocretin. Injection of hypocretin-2 was inactive due to rapid metabolism. On the other hand, injection of hypocretin-1 begets reduction in locomotor activity, which is dose-dependent. This effect in wild type zebrafish, as imagined, is abolished in hcrtr null mutant.

It seems the endpoint presentation of zebrafish lacking hypocretin receptor is contrary to narcolepsy in human. The pharmalogical outcome of hypocretin is right opposite to that in mammals, which promotes wakeness and increases locomotion. In regard to neuroanatomy, hypocretin receptor in zebrafish colocalizes with inhibitory neurons, rather than stimulating cell groups in mammals. I would like to quote the authors' words, this indicates "molecular diversity in sleep regulatory networks across vertebrates".

Wilfred Wu Wonderland [ Portal | 1996 edition | 2001 edition | 2006 Blog ]

Tags: zebrafish, model organism, developmental biology, sleep disorder, insomnia, narcolepsy, neurology, behavior biology, molecular biology, hypocretin, narcolepsy, orexin, hypocretin receptor, histology, hcrtr, hypocretin-1, hypocretin-2, HCRTR, pharmacology, hypothalamus, monoamine, monoaminergic, catecholamine, cholinergic, GABA, GABAergic, intracerebralventricular, evolution, conserved, diversity, phylogenesis, Medicine, Medicine-Molecular Biology, Medicine-Developmental Biology, Medicine-Behavior Biology, Medicine-Pharmacology, Medicine-Histology, Biomedical Science, Medical Science