1246 is the longer and stronger part of the cycle, and allow more time for the milk to flow. He then closes his mouth and swallows. There is such a short interval between these two actions that there could hardly be sufficient time for closing his jaws to cause his mouth to fill with milk-it must have filled during the preliminary sucking. The same cycle is followed when a child drinks from a cup with a rigid spout, when pressure achieves nothing. An adult finds it difficult and unnatural to swallow with his mouth open, so I suggest that the infant’s mouth closes as part of a coordinated swallow, and as relaxation from sucking, any biting action on the areola being purely incidental. There is another reason why it may help an infant to have the whole nipple inside his mouth-it enables suction to act laterally on the stretched ducts and so hold them open. This must be a far more efficient mechanism than merely sucking the tip of the nipple would be. That sucking is more important than biting or squeezing is demonstrated by the greater efficiency of the breast pump and nipple shield compared with manual expression. Both these instruments produce a better flow of milk, entirely by exerting negative pressure on an elongated nipple, and neither bites the areola. Naish wrote nearly twenty years ago, and it is time the Babies traditionally suck from the matter was settled. breast rather than bite it. Surely they still do if allowed
sucking
seems to
to
trv ? Jalan Pucang Anom Timur 70, Surabaya, Indonesia.
FELICITY KING.
SURFEIT OF SODIUM IN SOFTENED WATER
SIR,—In view of the concern regarding hypematraemia babies, I should like to draw attention to the
in bottle-fed
to the total sodium load which may be made In addition to the variable amount of sodium by in water from many sources, a considerable quanpresent tity of this metal is added during artificial softening by both the soda-lime and base-exchange methods. Domestic water softeners contain ion-exchange resins which substitute 2 sodium ions for each calcium ion. The softening of a hard water can result in a product containing 150-200 mg. per litre of sodium. Water from kettles which have been boiled repeatedly but not fully emptied will contain a higher concentration than tap water as a result of evaporation of steam. Human breast milk contains on average only 150 mg. per litre of sodium. Apart fromGold Cap SMA ’ all the currently available dried milks contain significantly more than this, yielding, when properly reconstituted, milks whose sodium content ranges from 225 to 690 mg. per litre. While the contribution of artificially softened water to a baby’s total sodium load is less than that from overgenerous use of these milk powders it may, nevertheless, be sufficient to tip the balance between its intake and the infant’s power
contribution water.
to excrete.
In deciding which baby milk to recommend, therefore, it would be wise to insist upon sodium-depleted milks at those homes and institutions which soften their water. Despite the well-known association between soft-water and mortality from cardiovascular diseases, some hospitals soften their drinking water. The needs of artificially fed neonates and of patients on low-salt diets provide an additional reason why this practice should be reviewed and discontinued. Scunthorpe Health District, Trent House, Hebden Road, Scunthorpe, Lincs. DN15 8DT.
J. S. ROBERTSON.
WEIGHT CARRYING AFTER MYOCARDIAL INFARCTION SIR,—Your contributors’ observations on weight carrying after myocardial infarction (May 17, p. 1113) bring to mind a recent patient in his forties who asked me a week " start his isometrics after his infarct whether he could again". At my request he demonstrated a series of muscletensing exercises which he had been taught as a means of body building. As I was acquainted with some of the research work quoted in the paper I reluctantly said " no". I do not know how widespread this cult is, but its existence supports the Edinburgh workers’ conclusion that one should try to distinguish between static and dynamic exercise in advising patients recovering from a heart attack. 96 Worcester
Road, Cheam, Surrey.
C. P. PETCH.
LEVAMISOLE AND LYMPHOCYTE RESPONSIVENESS levamisole (Jan. 18, p. 151) SIR,—Your editorial on " expressed the view that attempts to show a direct effect of levamisole on in-vitro responses of human lymphocytes to specific or non-specific stimuli have been either negative or unimpressive ". We have evidence that lymphocyte to P.H.A. can be augmented by levamisole. responsiveness This effect is related to the P.H.A. responsiveness state of the target lymphocytes. A total of 63 subjects were studied (10 blood-donors, 9 nasopharyngeal cancer [N.P.c.] patients, 11 " N.p.c." control patients [suspected of having N.P.c. but with no histopathological evidence of malignancy], and 33 pulmonary-tuberculosis patients [P.T.B.]). Lymphocytes (2 x 106) in 1 ml. Eagle’s medium (Commonwealth Serum Laboratories, Melbourne) supplemented with 10% fetal calf serum (F.c.s.) were preincubated with 50 µg. of levamisole (Janssen Pharmaceutical, Beese, Belgium) at 37°C for 18 hours and the cells washed twice before culture. Untreated lymphocytes were preincubated in medium alone. Lymphocyte activation by purified " phytohaemagglutinin (Burroughs Wellcome, England) was measured by net percentage incorporation of the y-emitting isotope 7sseleno-methionine (75Se-Me, Amersham) as a measure of de-novo protein synthesis. Lymphocytes (0-4 x 106) suspended in 1 ml. of methionine-free medium-10% F.c.s. were cultured for 72 hours at 37°C in a humidified atmosphere of continuously flowing 5% COJ95% air. P.H.A. (2-5 µg.) and 75 Se-Me (0-02003 µCi; 10,000-15,000 c.p.m.) were added at the start of culture. The mean ±1 standard deviation (s.D.) response of net 71 Se-Me incorporation of 42 blood-donors was previously determined to be 483 ±8.4%. Hyporesponsiveness was defined as a response more than 2 s.D. below the mean of blood-donors (i.e., < 315%). Replicate cultures showed a standard deviation of less than 25%, so a difference of greater than 2 S.D. (i.e., > 5%) in lymphocyte "
RELATION BETWEEN AUGMENTATION OF LYMPHOCYTE RESPONSIVENESS BY LEVAMISOLE’ AND P.H.A. RESPONSIVENESS STATUS OF UNTREATED LYMPHOCYTES
sucking
seems to
to
trv ? Jalan Pucang Anom Timur 70, Surabaya, Indonesia.
FELICITY KING.
SURFEIT OF SODIUM IN SOFTENED WATER
SIR,—In view of the concern regarding hypematraemia babies, I should like to draw attention to the
in bottle-fed
to the total sodium load which may be made In addition to the variable amount of sodium by in water from many sources, a considerable quanpresent tity of this metal is added during artificial softening by both the soda-lime and base-exchange methods. Domestic water softeners contain ion-exchange resins which substitute 2 sodium ions for each calcium ion. The softening of a hard water can result in a product containing 150-200 mg. per litre of sodium. Water from kettles which have been boiled repeatedly but not fully emptied will contain a higher concentration than tap water as a result of evaporation of steam. Human breast milk contains on average only 150 mg. per litre of sodium. Apart fromGold Cap SMA ’ all the currently available dried milks contain significantly more than this, yielding, when properly reconstituted, milks whose sodium content ranges from 225 to 690 mg. per litre. While the contribution of artificially softened water to a baby’s total sodium load is less than that from overgenerous use of these milk powders it may, nevertheless, be sufficient to tip the balance between its intake and the infant’s power
contribution water.
to excrete.
In deciding which baby milk to recommend, therefore, it would be wise to insist upon sodium-depleted milks at those homes and institutions which soften their water. Despite the well-known association between soft-water and mortality from cardiovascular diseases, some hospitals soften their drinking water. The needs of artificially fed neonates and of patients on low-salt diets provide an additional reason why this practice should be reviewed and discontinued. Scunthorpe Health District, Trent House, Hebden Road, Scunthorpe, Lincs. DN15 8DT.
J. S. ROBERTSON.
WEIGHT CARRYING AFTER MYOCARDIAL INFARCTION SIR,—Your contributors’ observations on weight carrying after myocardial infarction (May 17, p. 1113) bring to mind a recent patient in his forties who asked me a week " start his isometrics after his infarct whether he could again". At my request he demonstrated a series of muscletensing exercises which he had been taught as a means of body building. As I was acquainted with some of the research work quoted in the paper I reluctantly said " no". I do not know how widespread this cult is, but its existence supports the Edinburgh workers’ conclusion that one should try to distinguish between static and dynamic exercise in advising patients recovering from a heart attack. 96 Worcester
Road, Cheam, Surrey.
C. P. PETCH.
LEVAMISOLE AND LYMPHOCYTE RESPONSIVENESS levamisole (Jan. 18, p. 151) SIR,—Your editorial on " expressed the view that attempts to show a direct effect of levamisole on in-vitro responses of human lymphocytes to specific or non-specific stimuli have been either negative or unimpressive ". We have evidence that lymphocyte to P.H.A. can be augmented by levamisole. responsiveness This effect is related to the P.H.A. responsiveness state of the target lymphocytes. A total of 63 subjects were studied (10 blood-donors, 9 nasopharyngeal cancer [N.P.c.] patients, 11 " N.p.c." control patients [suspected of having N.P.c. but with no histopathological evidence of malignancy], and 33 pulmonary-tuberculosis patients [P.T.B.]). Lymphocytes (2 x 106) in 1 ml. Eagle’s medium (Commonwealth Serum Laboratories, Melbourne) supplemented with 10% fetal calf serum (F.c.s.) were preincubated with 50 µg. of levamisole (Janssen Pharmaceutical, Beese, Belgium) at 37°C for 18 hours and the cells washed twice before culture. Untreated lymphocytes were preincubated in medium alone. Lymphocyte activation by purified " phytohaemagglutinin (Burroughs Wellcome, England) was measured by net percentage incorporation of the y-emitting isotope 7sseleno-methionine (75Se-Me, Amersham) as a measure of de-novo protein synthesis. Lymphocytes (0-4 x 106) suspended in 1 ml. of methionine-free medium-10% F.c.s. were cultured for 72 hours at 37°C in a humidified atmosphere of continuously flowing 5% COJ95% air. P.H.A. (2-5 µg.) and 75 Se-Me (0-02003 µCi; 10,000-15,000 c.p.m.) were added at the start of culture. The mean ±1 standard deviation (s.D.) response of net 71 Se-Me incorporation of 42 blood-donors was previously determined to be 483 ±8.4%. Hyporesponsiveness was defined as a response more than 2 s.D. below the mean of blood-donors (i.e., < 315%). Replicate cultures showed a standard deviation of less than 25%, so a difference of greater than 2 S.D. (i.e., > 5%) in lymphocyte "
RELATION BETWEEN AUGMENTATION OF LYMPHOCYTE RESPONSIVENESS BY LEVAMISOLE’ AND P.H.A. RESPONSIVENESS STATUS OF UNTREATED LYMPHOCYTES
