Art and Science of Hunger

Knut Hamsun  wrote  Hunger in 1890(1).  This Norwegian novel, set in Kristiania( modern day Oslo) , recounts the wretchedness of an aspiring  writer caught in the clutches of hunger. His unsolicited  essays are more often than not rejected    by  the publishers, and even on the rare occasions when accepted the reward is just  enough to cover food for a couple of days.   Poverty forces him to pawn every possible material possession he owns.  Partly autobiographical, the tortuous feeling of  hunger,  what it can do to  the physical and mental state of a human being, is splashed across the pages in vivid shades. His mind is at once delirious and sober, indulging  in snobbish fantasies  while still being acutely aware of the stark reality around.  Traumatized by hunger he even takes to chewing bark.   Thirty years later Kafka sketched the  " Hunger Artist"(2)  For Kafka's protagonist abstaining from food is an art and  he does it willingly out of no compulsion whatsoever. Proud of his skill, he is ever ready to demonstrate it under the watchful eyes of the  public ,   seeks no reward and ultimately  fades into oblivion.

Experts say that  one’s daily energy need could be as low as 1600kcals or as high  as 6000 kcals depending upon how heavily one sweats it out. (3) Coupled activity of two key hormones, at the hypothalamus,  ghrelin at the opening ceremony and leptin  during the closing ceremony,   orchestrates our feeding pattern(4). In other words, ghrelin is the start signal and leptin is the stop signal.   It indeed isn’t surprising at all that intense research in the area of obesity  has been instrumental in unraveling the intricate biochemical and neural pathways of hunger. Friedman (5)   and his colleagues at the Rockefeller Institute were doing precisely the same in obese mice population,   when they confronted  leptin  It is astounding that the amount of  leptin generated is proportional to the fat stored in the adipose tissue. That means there is a dynamic inventory going on.

Mutations in the leptin gene or lesions in the hypothalamus regions where leptin is supposed to exert its influence could lead to hyperphagia, a state where the body is in perpetually hungry mode leading  to overeating and obesity. Ghrelin the hunger hormone too acts at the hypothalamus, specifically  on a set of neurons called Agrp neurons.  If the AGRP neurons are provoked into frenzied activity   then again  hyperphagia develops. However,  if somehow  AGRP neurons can be sedated, then  the result is aphagia, loss of appetite and abstention from food.  August 9^th issue of Nature carries a research paper by   Sternson and his team at the Janelia Farm Research Campus, Howard Hughes Medical Institute, Virginia, (USA), which tries to map the   neural circuitry of hunger.(6)  Their findings,  team hopes would prove helpful in  overeating disorders.

At the  Museo Nacional Centro de Arte Reina Sofia, Madrid  

1. Hunger by Knut Hamsun

2. Hunger  Artist  in Selected Short Stories of Franz Kafka, Srishti Publishers, New Delhi 

3. Biochemistry of Hunger 

4.  The role of leptin and ghrelin in the regulation of food intake and body weight in humans: a review Klok  Jakobsdottir  Drent ,  Obes Rev. 2007 Jan;8(1):21-34.

5. JeffreyFriedman 
6.The Deconstruction of a neural circuit for hunger : Atasoy, Betley and Sternson, Nature vol. 488, 9^th August, 2012, pages 172-177

Our Microbial Secrets

Microbiologists and those who intently study the origin and spread of infectious diseases are dismayed. millions of people, drawn from  widely different  geographical locations  gather together for sports events like the Olympics or  World Cup , or religious events like the Haj or Kumbh Mela   yet, no major outbreak of infectious diseases has been reported. The Hindu religious festival Kumbh Mela where over 70 million people reportedly gather  and  dip into the same ( albeit, flowing ) waters, is another such unique event. Though there are stringent  guidelines regarding vaccinations against varieties of infectious diseases, the health hazards can never be undermined. Hence there is a new interest on closely monitoring  such " Global  Mass Gatherings" and scientists put their heads together  recently  during a three day conference in Jeddah, Saudi Arabia, Oct 23—25, 2010 

Scientists are divided on their opinion.  The argument that sports events usually draw together hale and healthy youngsters with the best  built-in  immunity profiles, and hence the chances of infections are rare could indeed be valid. However,  that is not the demographic profile at religious gathering. So there is something hidden from view, which guards against. Kamran Khan a specialist in Infectious Diseases, at St. Michaels Hospital, Toronto, Canada, has been collecting data for quite some time on the Haj pilgrims. He admits, tha the Saudi Government  indeed went to great lengths to prevent any kind of human disaster by insisting on the necessary immunizations as part of the pilgrims travel plans, screening pilgrims  at the arrival points, quarantining and treating the sick at lightening speed.  He quotes figures for 2009,  at the peak of  H1N1 scare,  2.5 million pilgrims visited Mecca, and less than 100 were diagnosed with flu.  Could it be that we are too paranoid about microbes and infectious diseases?  ( I can’t help but drawing your attention to an earlier piece  “Befriending Allergens”, where we discussed the benefits of being  on "Hello, How are you?" terms with  other life forms and  chemicals)

So a new project has been initiated,  Human Microbiome Project.(HMP). This is along the lines of the   Human Genome Project ( HGP) initiated about two decades ago, to unravel the locational and functional  mysteries of the genes encoded along the length of the human DNA chain. That exercise is complete, and we have plucked all the low hanging fruits. However  lot more remains elusive and enigmatic and scientists are in pursuit. It is altogether another matter that the HGP also dealt a rather a severe blow to our vanity that less than 25000 genes are enough to define a human being, and that is as much as the mouse needs too. 

What does the HMP endeavor to achieve? Scientists are already aware that the human   body is  literally the universe for  trillions of microorganisms  that coexist within us and on us,  Extensive studies have been carried out on the microbial communities in the gut  and have necessitated  that we do acknowledge the service they render to us. The HMP, intends to go beyond the gut microbiota, and do the  microbial mapping of the entire human body. Known for the precise and systematic methods, scientists  are  being site specific: Ear, nose,  mouth, throat,  under arms, inside elbows………………

Initial results have shown that the the microbiota map is very different from individual to individual  and then  within each individual there are umpteen site specific variations, too. Are we gearing up for another blow? The HMP might reveal that " We are, but what our microbes make us to be.!"

Tailpiece
Robert Hook (1635-1703)( of course,  the Hook's Law fame)  gave us the first concise book on the minute bodies.  Armed with just  a microscope, he explored the realm of  micro dimensions.  The book was published in 1666 by Royal Society of London. And then in 1675, Antonie  Van Leeuwenhoek  (1632–1723) established that there are life forms, so small that they are not visible to the naked eye.  

http://en.wikipedia.org/wiki/File:Micrographia_title_page.gif

References:

1. Reflection and reaction The Lancet Copnference on Mass Gathering Medicine ,

      Lancet Infectious Diseases pp 818-819,  vol.10, 2010, McConnel and Memish

2. Infectious disease surveillance and modelling across geographic frontiers and scientific   

    specialties  The Lancet Infectious Diseases,  pp 222-230, Vol. 12(3).2012     

    Dr Kamran Khan MD, and others

3. Tackling the Microbiome, (Editorial, L Hood), Science , 1209 vol.336, 2012

4.  Do Sports Events Give Microbes a Chance to Score?, Kupferdchmidt. Science 1224- 

    25, vol.336 2012

5.  Science, All articles in the  special section 1245– 73 , Vol  336, 2012.

The Inheritance of Violence

According to Bible,   the very first murder  was committed by the very first  naturally born human .  The first  born of Adam and Eve,  Cain,   contrives to murder Abel, his own  brother, in a fit of jealousy.  Ever since that  first murder,   violence  has  became a part of human  life.   Violence must have been the quintessential quality of  the primitive  man,  when he had to coexist with the wild animals in accordance with jungle laws. Living in unfriendly terrains meant his  very existence depended on  his muscle power.  From the hunter gatherer,  as he,  ever so slowly,  metamorphosed  into a farmer,   he  acquired or rather developed certain extraordinary skills.   First of all he learned the  economics of  survival ,  the trade off between productive   foraging  versus  self annihilation.  Alienating himself from the jungle, he  tamed and domesticated  wild animals and plants  for his own selfish needs. As a part of  community living he also learned to communicate more effectively  with his kith and kin. The clicks and clocks of the tongue gave way to well structured languages   One would naturally conclude that language would have  at least to  some extent,  mitigated  mindless violence by facilitating   arguments  debates, discussions, negotiations and compromises.  

In fact Sigmund  Freud would have us believe that  man had to willingly suppress  his animal instincts,  especially the aggressive trait,  in order to set up a civilized society(1).     Incidentally I have been (re)reading the La Bete Humaine  ( The Human Beast)  written  in 1889 by Emile Zola (2).  The story is  set against the backdrop of industrial revolution and introduction fo railways in France.   The protagonist in the novel, Jacques, an engine driver,   is besieged with a violent urge to kill, whenever he tries to get intimate with a  female. He himself  is exasperated and deeply traumatized by this strange trait within. He tries to reason with himself, but  to no avail. At one point he concludes that this is a  trait inherited from the primitive man and can’t be just wished away.  

That is when  the issue of Science dated 18th May 2012 (3)  arrived with a  special section on violence.   Violence is analyzed and interpreted from various angles.  There is no conclusive evidence that civilized man is less prone to violence than the primitive man. There are enough arguments for and against.  This particular  issue of Science  is worth reading  not just once, but many times over.  In a  very concise yet incisive  editorial,  Professor David Hamburg  emphasizes the need to contain violence, as we contain a contagious disease. Look for early symptoms  and  prevent the spread then and there.  There is no single,  simple  answer to how violence erupts.  But with a  better sense of the after effects of  mindless violence, we should be  able to  " manage " it ;   this is the least we can do as human race . 

Scholarly essays  spread over  80 pages  deal very seriously with  the genesis and  developmental sociology of  human conflicts and violence.    But then  came relief  in the form of examples from animal kingdom.(4) Though we inherited the trait from them,  they don’t always resort to a "fight to kill  policy" to resolve conflict.  There are many other ways of  shooing  and scaring the enemy away, so  why fight to kill and be killed or injure and be injured?   Take the case of  Australian ants,  Iridomyrmex  purpureus,    They have a battalion of able bodied members forming the  Border Security Force, forever   safeguarding their territorial boundaries.  The  honeypot ants occasionally  hold power displays or  friendly matches  just to profess their  strength,  " Stay away, See what we are capable of".   And then  the practice  among the  green wood hoopoe,  a bird native to South Africa. Living in groups,  they defend their territories and  scare away intruders and enemies  by simply  calling as loudly as possible. 

1. Das Unbehagen in der Kultur   ( Civilization and its Discontents) S. Freud

2. La Bete Humaine ( The Human Beast)  Emile Zola

3. Science  vo. 336, 18 May 2012   pages 818-884
4. Elizabeth Pennisi, Science  vo. 336, 18 May 2012 , pages 828& 838

Nature's flower show at IISc Campus 

ICE ICE, BABY

 (View from Gulmarg: Photo taken on 13 May 2012 by PRC

It was not so long ago that we received a severe jolt  from the Intergovernmental Panel on Climatic Change (IPCC) that  the Himalayan glaciers  will be disappearing into thin year by roughly 2035.  This meant  serious  repercussions. Possibility of   rivers of Indian Peninsula and China, which originate from these glaciers, drying up, loomed large.  What an  unimaginable socio cultural, economic  and geopolitical  crises this would lead to ?  2035 is too close  a time frame  for comfort    and there  was frenzy all around.  I am sure there might have an unprecedented rush to visit the holy shrines and scenic places in the Himalayas before it was too late.    Fortunately for everybody , the preposterous hypothetical prediction was soon withdrawn,  with the  explanation that all parameters  that   govern the waxing and waning of glaciers  were not taken into account.   

Though almost akin to bank balance it is indeed it is very difficult to monitor the  credit and debit pattern in ( or of) glaciers.  Credit  accrual  is when snow fall and avalanche get deposited and  debit is through melting  and caving.   But  these don’t appear as neat line items on adjacent columns as in a bank passbook,  so that we can check out the balance easily.   (In a way it is as unpredictable as  foretelling the occurrence of  puddles  that  rains leave behind  along the length and breadth of  Bangalore roads. ).   Sure  there are so many unknown debits and credits, but then there  is so much of balance  as of now that we needn’t worry for the time being.  Still there are causes for concern.  Because  aren’t there  instances,  when family  wealth,  accumulated over generations, is often splashed away  by spendthrift  great grand children in a jiffy?

Hence it cannot be denied that global warming will  adversely affect the glaciers, however imperceptibly it might be.   Attempts  are being made by several scientific groups globally  to study this . Bolch et al (1) in the April 20^th issue of Science ask the pertinent question: How can we  make periodic,  three dimensional (length, depth and area) inventory of the  glaciers?.  In their opinion, location observatories, coupled with   remote sensing  techniques  and accurate modeling  would be one step forward.  Just as  the high and mighty Himalayas, Antarctic ice sheets   too  are  sending faint yet  sure signals of melting.  Pritchard et al ( 2) draw our attention to the fact that  the  repercussions may be felt   in a time frame of decades,  as an  infintesimal yet definite  increase in sea level.

Warm climates have ushered in  other unexpected ecological changes, so Pauli et al (3)would like us to believe.  Over a seven year period the team  monitored the  biodiversity (floral) across major mountain ranges in Europe.  The results seem to justify their  hypothesis that global warming might  drive plant species up the  mountain slopes. It would indeed be interesting to conduct a similar study along the Himalayan slopes.  First in the series should be " Is the Valley of Flowers receding ?"  Would be exciting to be part of such a scientific expedition.  

Europe has been closely monitoring  Mother Earth , through its eyes in the sky the  ENVISAT.   Since  2002 this satellite has been  providing European Space Agency (ESA)  with the vital statistics of Earth through a variety of multiply enabled instruments.  ESA received signals from ENVISAT till 8th of April 2012.  Since then there has been no contacts.  The implications are that the satellite's main computer or the power up system  might have failed. This has crippled a lot of agencies who are dependent on data from ENVISAT (4) 

Tailpiece :

Read about an interesting experiment to protect the glaciers of Alps.  Those concerned decided to  insulate them by wrapping them in  blankets ! 

 .http://environment.nationalgeographic.com/environment/global-warming/alps-meltdown/

References :

1.The state and fate of Himalayan Glaciers : Bolch et al  Science 20^th April 2012, Vol. 336, pages 310-314
2.. Antarctic ice-sheet loss driven by basam melting of ice shelves : Pritchard et al  Nature 26^th April 2012, Vol. 484 pages 502-505

3. Recent plant diversity changes on Europe’s mountain summits: Pauli et al  Science 20 April 2012, Vol. 336, pages 353- 355.

4. Europe loses sight of Earth : Brumfiel, Nature 26th April 2012, Vol. 484, page 423

4. Europe loses sight of Earth : Brumfiel, Nature 26th April 2012, Vol. 484, page 423

Evolution : FACTS and FUN

Evolution is a  serious  game in progress, of course at an impercetably slow pace. For us mortals, with short  life spans,   nothing really changes.   Mother Nature,  with her assistant  Natural selection, has been   playing the same game of speciation and divergence for close to 4 billion years. 

            One of the best fossils to study  various aspects of evolution   is the  simple tooth. (1).    In fact many extinct animals have left  behind only their fossilized teeth for us to know and  weave tales about them; how big  they might have been and what they would have eaten.  There are indications that though  jaws and teeth evolved independently, somewhere along the  evolutionary time lines, their pathways merged with the result that several things were firmly established once and for all.  The location of the teeth  on the jaws,  their function and  enabling dental features.  The frontal incisors and canines  help in  grasping and tearing, premolars and molars are  predominantly grinders, though they can also cut.   Cusps, the conical projections    on the surface of the molars  are   the enabling features to aid grinding and cutting process.    From the single cuspid reptilian to multi cuspid mammalian, there  are large variations in the dental features between species, but  relatively less within a  given species.   

            Harjunma et al(2) were fascinated by the developmental biology of  molars in laboratory mice.  Mice teeth are limited to   incisors and molars. In laboratory bred  mutant and transgenic mice very often cusps  are totally absent.  Except aesthetics,  these flat teeth may not have much functional use. Poor mice, flat teeth would have  robbed them off the whole  enjoyment of eating.  But why flat teeth, what leads to such a strange situation?.  Scientists have identified at least 29 gene mutations which can affect teeth formation in multiple ways, absence of cusps included. Mutation (altered  message) is one thing and signalling, (sending the message across to  intended recipients) is another thing.  Signals are clues to  turn on or turn off  or slow down  specific biochemical processes.   Tinkering with three such signalling pathways simultaneously   the team could ultimately increase the number of cusps even beyond the normal.   Harjunma team suggest that  there could be  multiple genes  at work in imparting cusp pattern to molars.  Adjusting  three genes they could make the cusps reappear, but then, in all possibility,  something else might have  gotten  impaired ?  No wonder evolution is a slow process, it is so intricate, so many messages need to be so finely balanced.......
 A friend of mine, who is working in the area of drug research,  spoke to me recently about   the  long years of study needed to zero in on a drug molecule.  A very promising  drug molecule  may prove to be causing some other ailment as a side effect. For example it might cure cancer but might lead to blindness. That is not acceptable.  Biological signals are never dedicated " For your eyes only"  type. One single signal  might be meant for several recipients and each  recipient  might interpret it in a different way. Hence the need for fine coordination. And that takes enormous amount of time.  

“Tailpiece”

Playing the same game for close to 4 billion years  is not  a joke. Boredom is sure to  creep in at times and  that  is when Mother resorts to a few naughty tricks and treats. Her lazy assistant Natural Selection lets the players fight it out for survival, to decide   who wins and who gets wiped out.  Evolutionary biologists of course would  interpret these  as are necessary and well orchestrated  examples of  adaptive evolution, or survival tactics.   But just imagine wouldn’t it  be more fun to accept these as simple acts of pranks?  Take for example.  the rampant  practice of mimicry(3,4): the   Australian insect which resembles a twig,  the harmless hoverfly  which imitates the looks of the  sting bee,    the  venomous Texas coral snake and its innocuous twin, the  Mexican milk snake. 
More about mimicry  later 

1.Evolution and development of teeth McCollum et al   J. Anatomy. 2001 199, pp. 153-159

2. On the difficulty of increasing dental complexity: Harjunmaa et al Nature 2012, March 15, 483, 324-326.

3. Comparative analysis of the evolution of imperfect mimicry  Penney, H D et al, Nature 2012 March 22,   483, 461-464

4. A taste for mimicry ; Ruxton et al  Nature 2005 , January 20 ,  433 205-206

Social Networking: From Paleolithic to Facebook Era ........

Hadza(1) is a fast disappearing aboriginal tribe in Eastern Africa; Tanzania to be precise.   Hunters and gatherers for several thousands of years,(naturally, women are the gatherers and men the hunters) they communicate through clicks(2). They live  usually in small  groups of about 25.  The groups are loosely knit; members could come and go as they please, no questions asked nor answers sought.  Personal freedom is at the zenith.   Married couple can opt out of matrimony by living separately  for a fortnight, or by  adopting  the dress code of the  unmarried.   To  our civilized myopic eyes their  social norms or traditions are just a blur or altogether nonexistent.   

In forager societies there is no concept of personal wealth.  They live for the present, no hoarding  or saving.  Hunting is not an individual, but a team  effort, so also consuming the  prey.  Gathering may be a n individual effort, but the amount gathered is  so much that it is   shared.    How does such a group come together? Or rather  what holds such a heterogeneous  group (of  young and old, men and women,  active and lazy) together?   There indeed has to be a high degree of give and take or in modern terminology  Cooperativity.  Do like minded members seek out  each other ?  Are conflicts always settled by those with divergent views moving out?     Apicella and team  (3) reasoned that this is a  ideal system to study the intricacies of human interactions   since  prehistoric times. Because the Hadza haven't changed their ways in the least bit except perhaps  discarding the animal skin loin cloth for the manmade fabric. 

The  research paper published in January issue of   Nature (3)  reports   the social   networking pattern among Hadza tribe. 205 adults (men and women)  spread over 17 groups  were studied.  The sample size may not appear statistically significant;  yet considering the dwindling population, there  indeed is no other option but to accept. The affinity between individuals within the group and  outside group  and their voluntary contributions  for  a common cause came under scrutiny.  The methods used might sound a bit trivial. For example person to person affinity was  measured in terms of  sharing /gifting honey sticks ( high prized item among Hadza) and  choosing a preferred  group mate from a set of photographs.  The team concluded that  cooperativity is the glue that holds a group together. This could spring from  genetic,(parents, siblings, cousins) affinal (marriage)  ties or simple friendship.  They found cooperators  tend to flock together,  and often influence the  non-cooperators to fall in line, or else, get left out.   There is always an undeniable  element of  emotional quotient  when humans are involved. Somehow that seems to be absent in this study.   

  

If cooperativity  is at the core of social networking during prehistoric times, is it relevant today too? What better social networking site than the Facebook, a  vast network of friends and friends’ friends.?  Lewis et al (2) mapped  more than 1500 jottings by college students over a 4 year period, from the time they first entered the college till  they graduated out.  In principle could as well  be  a ‘Developmental Sociology”  project.  Lewis and team are cautious in the anlysis and interpretation of their data.   They did observe  is a tendency to seek out those who have similar tastes in music and films  however no trend to influence others. 

(1) Hadza_people

(2) Click_consonant

(3)Social networks and cooperation in hunter-gatherers: Coren Apicella, Frank W. Marlowe,James H. Fowler and Nicholas A. Christakis,  Nature 2012 481,497-501

(4)Social selection and peer influence in an online social network :

Kevin Lewis, 

Marco Gonzalez, 

and Jason Kaufman,   

Proceedings of the National Academy of Sciences 2012 109 (1) 68-72;

In step with elephants

Switching between walking and running seem natural to us  but  technically  these are   two different activities. Locomotion, which includes walking, jumping and running is an important topic in biomechanics.  Intense  research in the field  of gait analysis   has helped   orthopaedic medicine a great deal  to not only to  treat and  cure but also to  improve  the designs of orthopaedic aids for  the injured and the handicapped.   Also assumes great significance in sports medicine.

The movement of the centre of mass (COM) of the body, the contribution from potential and kinetic energies and  absence or presence of an airborne status  these are the features  that  distinguish a Walk from a Run.  During  walking  the COG moves in a curvaceous manner from side to side akin to an inverted pendulum, as feet take turns to be grounded and airlifted,  there will be fleeting yet recurring moments when both feet are on the ground, and potential and kinetic energy contributions are out of phase.   During  running the COM is bobbing up and down like a bouncing ball,  there are moments when the entire body is suspended in air,  the potential and kinetic energy contributions are in phase and the kinetic energy demands soar.  The same criteria hold good for quadrupeds too. 

While the fleeting airborne status during running is indeed a reality for  humans or agile quadrupeds such as deer or tiger,  could this be true for   elephants too?   Two teams one headed by Professor  Norman Heglund from the Université catholique de Louvain, Belgium  and the other by  Professor John Hutchinson  (  Department of Veterinary Sciences  and  Structure and Motion Laboratory  Royal Veterinary College, London,)  set out to study the way  elephants negotiated distances at slow and faster paces.  The question to be settled was “ do they walk,  or run?”  

A complex proposition indeed. To understand the complexity in its entirety, just  have a look at the  animal   itself.  A mature bull elephant could weigh as much as 5000kg and stand tall at a  3 meters. Give and take a 1000kg or a meter  depending on the generic  and gender variations.   Elephant  legs are  cylindrical columns, in more  precise terms   load bearing pillars; tall, fat and  straight. The feet circumference could range of 120-140 cm.  The front  foot  is quite circular in shape, and the rear  a bit  oval.  Composed mostly of elastic fibrous tissue these are very efficient shock absorbers too. Anyway,  with such proportions it is not easy to have a graceful gait, yet elephants walk majestically. But can they really run?

.

To monitor the gait features of the heaviest animal on earth,    Heglund and team decided to construct a test rig at the  Elephant Conservation Centre (ECC) in Lampang, Thailand.  As Heglund  puts it “an 8 m long, elephant-sized force platform from sixteen 1 meter square  force plates.”  Force plates are devices which work on Newton's Law that every action has an equal and opposite reaction. Complete with transducers,  cameras and computers it measures the ground reaction forces exerted as one  walks on it .  The entire set up   was custom built in  Belgium and shipped to  ECC,  where they  were assembled over a sturdy reinforced concrete platform in the middle of a long gait track.  

It must not have been easy to get the elephants  walk over the  desired path.   They must have  needed excessive coaxing by their mahouts.  Even then  instigating them   to  charge forward  onto  the test rig must have been no less than  close encounter with danger. A herd of 34 elephants including a baby of  870kg  and an adult of 4000kg finally  participated in the experiment.  Speed profiles and  corresponding energy diagrams over the center of mass were recorded for each one separately. 

Now to the results:  believe it or not the elephant  is indeed a very very energy efficient  animal.  The team found out  that  the energy expenditure on locomotion for an  elephant’s  is 1/3rd that of humans and 1/30th that of mice.  Elephants  take quicker steps; ( high “step frequency”).   At slow pace they have 3 feet grounded and in  "faster mode " have two feet on ground. While this effectively keeps the COM  displacement  and hence energy requirements to a minimum,    doesn't  qualify for running; because the mandatory  airborne phase is absent.      However energy diagrams recorded a slight vertical displacement   of  the center of mass ( bouncing),  characteristic of trotting during the second half of the gait cycle! 
Ha so the elephant walks as it trots!     

1. Biomechanics of locomotion in Asian elephants J Exp Biol 213, 694-706.2010, Genin et al

2. Integration of biomechanical compliance, leverage, and power in elephant     limbs    Proc. Natl. Acad. Sci. USA 2010 107:7078-7082. Ren et al

3. .http://mathaware.org/mam/2010/essays/TongenWunderlichRunWalk.pdf

4. http://www-personal.umich.edu/~ferrisdp/Farley&Ferris,1998.pdf