1892 



II WDBOOK !>!• I'lh SIllI.OGY 



M i ROPHYSIOLOGY III 



neural metabolism (through producing low blood 

 sugar or a deficiency of souk- vitamin), or indirectly 



by routes such as disproportionate bone growth (as in 

 vitamin-A deficient pups). Nutritional deficiencies 

 resull in a variety of lesions in the brain, spinal cord 

 and peripheral nerves (771, including the destruction 

 of the myelin sheaths of nerve fibers (223, p. 700). 

 Many of these changes are not specific. Thus demye- 

 lination was reported in conditions varying from 

 starvation alone (in rats) through deficiencies of panto- 

 thenic acid and pyridoxine (in chicks, mice and pigs) 

 to copper deficiency (in lambs). 



The existence of large differences in the rate of 

 oxygen consumption in different parts of the nervous 

 system and the species differences in nutritional re- 

 quirements complicate the assessment of neuro- 

 physiological responses to dietary deficiencies. Thus, 

 the respiration of the brain cortex is some 30 times 

 greater than that of the peripheral nerves (86), and 

 within the central nervous system of the adult there is 

 a fairly steep quantitative metabolic gradient from 

 cerebral cortex to brain stem, cerebellum and medulla 

 (106, p. 164). 



In nutritional deficiencies the alterations of nervous 

 timet ion depend on the duration of the deficiency 

 and the magnitude of the difference between the 

 amount of nutrient available and the physiological 

 requirement for it. This accounts, in part, for the 

 differences between results reported by different 

 investigators. From the practical point of view the 

 time parameter is very important. Nutritional de- 

 ficiencies that require months to produce symptoms 

 are of no concern in evaluating performance capacity 

 of men maintained for a few days on emergency 

 rations, while the) may be of crucial importance for 

 populations on chronically deficient dins. 



In addition to alterations of nervous function 

 resulting from nutritional deficiencies, it is necessary 

 in consider also abnormalities, nutritional in origin 

 but not caused by deficiencies, Mich as the spastic 

 paralysis of lath) rism. 



ACUTE STARVVI 11 i\ 



From the point ol view of dietary control, acute 

 starvation (complete withdrawal of food with free 

 access in water) is the simplest nutritional deficiency. 

 \i the same time it is perhaps the most complex one 

 mm tabolicaily. In the older literature 1 182, p. 22 |) a 

 variety "l histological changes in the nervous system 

 were reported and interpreted as degenerative altera- 



tions resulting from inanition. Liu & Windle (149), 

 however, found that brains of starved guinea pigs 

 differed from those of control animals in surprisingly 

 few details, among which were reduced amounts of 

 Nissl substance in some of the large nerve cells of the 

 brain stem. 



An exploratory stuck with starved and subse- 

 quently re-fed guinea pigs suggested that the retention 

 of a learned task (running an alteration maze) was 

 not impaired (149). Total food deprivation increases 

 for a time the general activity of an animal, as meas- 

 ured in rats by means of revoking drums (72). In 

 dogs withdrawal of food for 4 to 6 days results in 

 diminished sexual interest, shortened duration of 

 sexual conditioned reflexes with increase of latent 

 period, and a partial or complete loss of conditioned 

 ejaculation (81 ). 



Around the turn of the century, various "hunger 

 artists' went through prolonged fasts with surprisingly 

 unimpressive signs of deterioration (138). In contrast 

 to these men who kept their energy expenditure at a 

 low level, marked changes were found in young men 

 undergoing 4 days of starvation combined with hard 

 physical work (105). In regard to their manipulative 

 performance (29), statistically highly significant 

 deterioration was noted in tests of speed and of 

 coordination. Interestingly enough, there was no 

 decrement in hand grip and the decrements in back 

 pull did not reach a level of statistical significance. 

 Body sway increased substantially. Tests of intellec- 

 tual functions showed little or no impairment. The 

 principal subjective symptoms and complaints in- 

 cluded tiredness, "weakness' (not demonstrated by 

 strength measurements) and decreased ability to 

 concentrate. The men fell sleepy and their self- 

 initiated activities decreased Nausea was a common 

 complaint after the exhausting runs on the treadmill. 

 In spite of the availability of water, the men com- 

 plained of dryness of the throat. 



From the metabolic point of view, the alterations 

 thai may account for the initial changes in nervous 

 and motor function include the lowering ol blood 

 sugar, kelnsis and dehydration (270). In advanced 

 diabetes, with acidosis and ketosis, a profound (40 

 per cent) reduction in cerebral utilization of oxygen 

 takes place in the presence ol undiminished cerebral 



blood How and a normal arterial oxygen saturation 

 1 ;o). The accumulation of ketone bodies in the 



blood of individuals in the advanced Stated Starvation 



mav lead to a severe disturbance of cerebral metabo- 

 lism and function. 



