The Pharmaceutical Journal
Vol 273 No 7307 p66
10 July 2004

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The curious incident of the hippo in the sunshine more
“Alas, our young affections run to waste” more
Depression strikes East Asian nations more
Sound definition more

The curious incident of the hippo in the sunshine

In the 27 May issue of Nature a group of Japanese scientists describe the curious changes in skin pigmentation that occur in the hippopotamus when exposed to the heat of the sun. The viscous sweat, initially colourless and alkaline, gradually turns red and then brown, becoming highly acidic, as compounds present polymerise. These unstable red and orange pigments are non-benzenoid aromatic compounds with antibiotic, antiseptic and sunscreen activity. The fluid secreted by the skin of the animal cannot strictly be called sweat, since it is produced by subdermal cells. Nevertheless it performs the same function of helping to control body temperature.

The researchers collected the red secretion by wiping the skin with gauze and extracted it with water. Purification by gel filtration and ion-exchange resin treatment yielded two pigments, one red, the other orange. The red pigment was named hipposudoric acid and the orange one nor-hipposudoric acid. Their biochemical derivation was probably by oxidative dimerisation of homogentisic acid, a metabolite of the aminoacids phenylalanine and tyrosine. These natural pigments are likely to exist in anionic forms in the hippopotamus’s alkaline sweat, probably stabilised by intermolecular hydrogen bonding with the solvent carrier.

The pigments, showing spectra in the range 200-600nm, presumably act as sunscreens. The red one demonstrates the antibiotic activity observed and, at lower concentrations than those found in the hippopotamus skin, inhibits the growth of Pseudomonas aeruginosa A3 and Klebsiella pneumoniae. Both pigments are highly unstable, but after drying on the skin surface in the presence of mucus maintain their colour for several hours before polymerising into brown solids.

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“Alas, our young affections run to waste”

In Nature for 17 June there is an essay by Melvin Konner, an anthropologist from Atlanta, on the nature of the bonds between humans which we designate by the name “attachment”.

Although bonds of affection have held families together since the dawn of human time, attachment has only recently become a subject for scientific study. Sigmund Freud, writes Konner, said a great deal about how the mind handles the topic of sympathetic attachment, and predicted that “our provisional ideas in psychology will some day be based on an organic substructure”.

The basic attachment, it has been said, is the link between mother and infant, something that has developed during centuries of evolution. In all cultures the typical attachment behaviours, like clinging to a primary care-giver in times of distress and recognising the essential privilege of that person to relieve anxiety, becomes powerful during the second half-year of life. It has been observed that during that phase of infancy the major pathways of the brain’s limbic system become coated with myelin, which improves the function of those subcortical circuits that process emotion, together with their nervous connections with the frontal and cingulate cortex.

In many mammals, though not humans, oxytocin plays a role in maternal responses to infants. The attachment between males and infants, on the other hand, involves the activity of vasopressin, which is also a brain neurotransmitter. Experiments in prairie voles indicate that mating is promoted by vasopressin.

It seems possible that long-term commitment between humans is determined by these two hormones. Treatment with them might be effective in counteracting the condition known as “reactive attachment disorder”, which is responsible for abnormal personal relationships of children who have undergone social trauma during infancy.

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Depression strikes East Asian nations

An account by Carina Dennis in the 17 June issue of Nature of the strange spread of mental illnesses, and particularly depression, in East Asia, gives grounds for some anxiety.

The incidence of suicide among elderly residents of China is reported as shocking, while a wave of social phobia that prompts youths to lock themselves in all day and play computer games all night has afflicted Japan. There appears to be a general upward swing in the rate of mental illness in East Asia. In Japan this is said to coincide with the emergence of an underclass of unemployed youths.

At the same time, many Asian nations are ill-equipped to offer specialist care for the rehabilitation of sufferers from neurotic ailments. Another factor believed to contribute to this situation is the tendency of people of Asiatic stock to possess a genetic makeup which makes them react differently to the antidepressants and antipsychotics that have been used in the West with success. Despite recently published World Health Organization data suggesting that people in China and Japan are less liable to depression and related disorders than those in the West, the suicide rate in Asia is one of the highest in the world, with some 300,000 Chinese, mostly in rural areas, killing themselves each year.

The high suicide rate has been attributed to the changing socioeconomic climate in the East, which has resulted in diminished security, rising unemployment and a breakdown of traditional family and community networks. Meanwhile, substance abuse, frequently associated with mental instability, has increased. A recent addition is eating disorders, once considered to be a Western phenomenon.

East Asia has a shortage of doctors trained in mental health problems and poor diagnostic facilities. Individuals tend to report only physical symptoms and not psychiatric signs. Mental illness is regarded as a moral weakness rather than a treatable condition and care in the community is rarely available. Most antidepressant drugs available are considered obsolete by Western standards and Asian individuals often react adversely to them on account of different modes of metabolism. Moreover, many Asians are used to taking herbal remedies that could interact with the medicines they may be prescribed. All these are factors that complicate the treatment of depression.

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Sound definition

‘‘Opiate. An unlocked door in the prison of identity. It leads into the jail yard.”
—Ambrose Bierce: ’The Devil’s Dictionary’ (1911).
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