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DIURNAL EXCRETORY RHYTHM

Soon after birth a daily cycle of behaviour is estab--lished in relation to sleeping, waking, and feeding withsubsidiary patterns of diurnal rhythm affecting otherphysiological functions. These include body-temperature,white blood-cell population in peripheral blood, carbo-hydrate metabolism, renal excretion of adrenocorticalsteroids, and renal excretion of water and electrolytes.The excretory cycle of water and electrolytes has been

known and investigated since 1877.1 During the nightthere is a diminution in the renal excretion of water,sodium, potassium, chloride, and bicarbonate with a fallin urinary pH and a rise in urinary ammonia and titrableacidity.2 In the morning there is an

" alkaline tide " inthe urine ; this is unrelated to the gastric secretion ofhydrochloric acid since it occurs despite achlorhydria orfasting. In addition there is a rising output of water andelectrolytes, which reaches a peak about midday with asubsequent fall and a minimum output during the night.This complex cycle depends on fluctuations in renaltubular transfers of ions, since in the normal person thereis little or no change in renal hæmodynamics (renal blood-flow and glomerular filtration-rate) or plasma-ion levelsthroughout the twenty-four hours.3 While one might betempted to ascribe the diurnal rhythm to a cycle ofadrenocortical activity, as evidenced by diurnal variationof eosinophils in peripheral blood and of urinary excretionof adrenocortical hormones, the evidence is against thispossibility.4 The diminished pulmonary ventilationassociated with sleep, and the resulting acidæmia, maybe the factor determining the cycle of renal tubularfunction.2 It is well known that, in acute experiments,hyperventilation and the resulting alkalaemia producepronounced changes in renal ion clearances, though theseare not quite comparable to the altered ion clearancesbrought about by waking.

Attention has lately been focused on the reversal ofthe diurnal rhythm of water and electrolyte excretion incongestive heart-failure accompanied by oedema andcirrhosis of the liver with ascites.5 In such patients,however, it is noteworthy that there is an associateddiurnal rhythm in renal haemodynamics with maximumrenal blood-flow and glomerular filtration-rate at night. 6This may possibly be related to changes of posture oractivity during the twenty-four hours. Such a renal

hsemodynamics cycle, rather than an altered cycle inhormonal control of renal tubular ion transfers, mayaccount for the reversal of diurnal rhythm of water andelectrolyte excretion.

Our knowledge concerning the mechanism of thenormal diurnal rhythm and its reversal in disease statesis still incomplete. Will further research provide cluesto that all-important problem-the unknown mechanismthat controls the volume of extracellular fluid ? ’?

1. Quincke, H. Arch. exp. Path. Pharm. 1877, 7, 115.2. Stanbury, S. W., Thomson, A. E. Clin. Sci. 1951, 10, 267.3. Sitota, J. H., Baldwin, D. S., Villarreal, H. J. clin. Invest. 1950,

29, 187.4. Rosenbaum, J. D., Ferguson, B. C., Davis, R. K., Rossmeisl,

E. C. Ibid, 1952, 31, 507.5. Jones, R. A., McDonald, G. O., Last, J. H. Ibid, p. 326.6. Baldwin, D. S., Sirota, J. H., Villarreal, H. Proc. Soc. exp.

Biol., N.Y. 1950, 74, 578.

ADVANCES OF SCIENCE

SCIENTISTS must recall with sympathy the plight ofthat wrecked sailor who had so many things that hewanted to do that whenever he thought he would like tobegin he couldn’t, because of the state he was in.

Luckily for us. or possibly unluckily, they have notstumbled on his masterly solution—which was to do

nothing but basking until he was saved. Members of the13riti.,Ii Association for the Advancement of Science, nowmeeting in Belfast, have so much to tell each other, andon such very different topics, that opportunities for

basking must be strictly limited, despite the indulgentand excursive hospitality of their hosts, and the factthat the Mountains of Mourne are performing theirwell-known feat only a short drive away.

But, indeed, it is doubtful whether scientists are inthe mood for basking. A hundred years ago their fore-runners could carry their calling lightly, looking confi.dently forward to a benefited world. Today, as Prof.A. V. Hill, F.R.S., the president of the association, saidof their ethical dilemma, " science finds itself unexpec-tedly and without those centuries of tradition and

experience in a position no less important to the com-munity than medicine : and its ethical principles havenot yet clearly emerged." There seems, he concluded,to be no simple answer. Scientists are naturally as

anxious about this as the rest of us ; but they haveaccepted the duty of using their minds as well as theycan to discover the nature of the universe, and like therest of us they take refuge in their work.

Certainly they have plenty to occupy them.’ Theirprogramme at Belfast contains no specifically medicalsection, but various sections touch on medicine—notablythose on chemistry, zoology, physiology, psychology, andagriculture. Subjects of interest to doctors include suchthings as the control of the movements of the alimentarycanal, the chemistry of bread-making, the assessment ofpersonality, and Britain’s food-supplies. In speaking ofthe problems of parthenogenesis, Prof. A. D. Peacock,D.SC., was not perhaps discussing a subject of immediateconcern to us, but he raised some interesting speculations.In the last year, he recalled, G. Pincus and his associateshave been responsible for the development of sevenrabbit parthenogones; all were female, five were bornalive, and one has since produced a litter of nine afternormal mating. Pincus sees a possible application of theprinciple in stockbreeding : if cows could be made tobreed females by parthenogenesis it would be extremelyconvenient.

1. Blalock, A., Taussig, H. B. J. Amer. med. Ass. 1945, 128, 189.2. Brock, R. C. Brit. med. J. 1948, i, 1121.3. Brock, R. C., Campbell, M. Brit. Heart J. 1950, 12, 377.4. Brock, R. C., Campbell, M. Ibid, p. 403.5. Blalock, A., Kieffer, R. F. Ann. Surg. 1950, 132, 496.6. Potts, W. J., Gibson, S., Riker, W. L., Leininger, C. R. J. Amer.

med. Ass. 1950, 144, 8.

VALVULOTOMY VERSUS SHUNTCYANOTIC congenital heart-disease is nowadays treated

surgically in centres all over the world as a result ofthe pioneer work of Blalock and Taussig in Baltimore.Because these unfortunate patients can now be relieved,partly or completely, of their disabilities, interest has

quickened greatly. The rapid advances in such tech-niques as cardiac catheterisation and cardioangiographyhave made it possible to reach an accurate preoperativediagnosis in almost every case ; but there remains the

question of which operation will afford the best result.The shunt operation of Blalock is ideally suited to

cases of severe pulmonary atresia or of tricuspid atresia.Pure stenosis of the pulmonary valves, however, clearlyinvites a more direct approach to widen the stenosedopening ; and this Brock 2 3 has most successfullypractised. The problem now before the cardiologist andcardiac surgeon (for it is imperative that they worktogether) is which patient will derive most benefit froma subclavian-pulmonary anastomosis, and which froma direct valvulotomy or infundibular resection of thestenosed area. Pure pulmonary valvular stenosis (i.e..not associated with an interventricular septal defeet is best treated by Brock’s direct attack on the stenosedopening with a valvulotome.5 6 A Blalock shunt i?contra-indicated since sooner or later right-sided heart-failure develops because the strain on the obstructedright ventricle is unrelieved. On the other hand, withatresia of the tricuspid valve so little blood enters theright ventricle that this is largely functionless. and

pulmonary valvulotomy will be useless. In such patients