LYMPHOCYTE-MEMBRANE ADENOSINE TRIPHOSPHATASE

LYMPHOCYTE-MEMBRANE ADENOSINE TRIPHOSPHATASE

1017 all the characteristics imputed to " high renin hypertension ". No distinction would appear to be demonstrated yet in terms of reversibility, whe...

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1017 all the characteristics imputed to " high renin hypertension ". No distinction would appear to be demonstrated yet in terms of reversibility, whether oncotic mechanisms are active or not. Resetting in general could be by neurogenic or structural vascular resistance.

(reversible)

Department of Medicine, University College Hospital, Ibadan, Nigeria.

(irreversible)

increase in renal

In view of the interest in the enzymes involved in the events in lymphocyte stimulation, particularly as evidenced during the recent 2nd International Congress of Immunology, it is tempting to speculate that the particulate sites of A.T.p.ase activity might correspond to the location of the antigen-recognition sites.

early

This work is supported in part by the American College of Surgeons Schering Scholarship.

RAYMOND CARLISLE.

TERMINATION OF FIRST-TRIMESTER PREGNANCIES SIR,-May I support the plea by Mr Maresh and others a consideration of outpatient termination of first-trimester pregnancies. I have, for the past two years, run a very successful service on these lines at Dryburn Hospital, Durham, which I propose to report more fully later. The five conditions laid down in that paper have been fulfilled in almost all our cases, and so far we have terminated, on an outpatient basis, some 420 pregnancies, with no mortality and very little morbidity, and it would seem, from my experience, that the inpatient termination of first-trimester pregnancies under general anxsthesia is uneconomic and totally undesirable from other aspects than that of finance.

Departments of Surgery and Cardiovascular Surgery, Stanford University, Stanford, California 94305, U.S.A.

ALAN S. COULSON VIRGINIA H. ZEITMAN R. COHN RANDALL B. GRIEPP EDWARD B. STINSON NORMAN E. SHUMWAY.

(Oct. 12, p. 888) for

Dryburn Hospital, Durham DH1 5TW.

STANLEY WAY.

LYMPHOCYTE-MEMBRANE ADENOSINE TRIPHOSPHATASE SiR,-It has been postulated that adenosine triphosphatase (A.T.p.ase) in the cell membranes of small lymphocytes may be related to the antigen-recognition sites and may participate in the early events in lymphocyte stimulation.1 A fuller knowledge of the lymphocyte triggering system may pave the way for more specific inhibitors which could be of value as immunosuppressives in transplant

recipients.2 Using a modification of McClurkin’s technique3 a sodium/potassium-dependent A.T.p.ase activity was demonstrated in small lymphocytes freshly separated from human peripheral blood. The activity was confined to the cell membranes and to related clusters of small dots, and The number and density of was inhibited by ouabain. the dots varied from donor to donor, as did the percentage positivity of the lymphocytes. Earlier studies on lymphocyte-membrane enzymes have shown that non-specific cholinesterase is similarly localised on the small lymphocyte membraneswhereas cyclic 3’,5’-A.M.p.ase is situated on the nuclear membrane.s Ellegaard and Dimitrov 6 demonstrated the existence of two different A.T.p.ase activities in homogenates of human lymphocytes, and one of these was also ouabain-sensitive and possibly associated with the cell membranes. Earlier studies indicated that the membranes of transformed lymphocytes exhibited A.T.p.ase activity 7.8; in contrast, our studies have concentrated on small lymphocyte membrane enzymes before stimulation. 1. 2. 3. 4.

Coulson, A. S. J. theoret. Biol. 1969, 25, 127. Coulson, A. S., Inman, D. R. Guy’s Hosp. Rep. 1971, 120, 89. McClurkin, I. T. J. Histochem. Cytochem. 1964, 12, 654. Coulson, A. S. in Proceedings of the Fifth Leucocyte Culture Conference (edited by J. E. Harris); p. 235. New York and London, 1970.

5. 6.

Coulson, A. S., Kennedy, L. A. Blood, 1971, 38, 485. Ellegaard, J., Dimitrov, N. V. Br. J. Hæmatol. 1973, 25, 309. 7. Gropp, A., Fischer, R. Virchows Arch. path. Anat. 1964, 338, 64. 8. Fries, D., Bryon, P. A., Brunat, N., Brochier, J., Revillard, J.-P., Traeger, J. Path. Biol., Paris, 1967, 15, 250.

INTESTINAL POTENTIAL DIFFERENCE DURING GLUCOSE ABSORPTION

SiR,—Among Dr Wingate’s comments (Sept. 28, p. 787) intestinal potential differences (P.D.) generated by the absorption of glucose in manIwas surprised to find that I was charged with a previous " opposition to the clinical use of such methods " and that my involvement in the studies represented a volte-face. Even accounting for the poetic licence of Dr Wingate’s humorous and colourful style, such statements are an idiosyncratic interpretation of my previous writing on the subject and take little account of subsequent experimental work in animals correlating operational kinetic indices of electrogenic absorption obtained by chemical and electrical techniques. 2,3 May I clarify the position as I see it. Geall and Summerskill4 discussed, in 1969, the published studies on the electrical P.D. across the bowel and pleaded

on

for its measurement in various disorders on the basis that the P.D. may correlate with the disease processes. My comments5 on their article began: " While the plea ... merits strong support a degree of caution is needed in the interpretation of data obtained from ... studies in the small intestine ". I questioned the sensitivity of the transmural potential as an index of intestinal malfunction and suggested that one way of answering this was to review the available studies so that " if the change in potential is related to the changes in structure and function then clearly it is a useful measure of integrity... if, however, there are no or very small changes ... its use must be limited ". Many of the studies I then listed revealed that though the absorption of various solutes was altered the P.D. was unchanged when measured usually at a single concentration of luminal hexose or aminoacid or in their absence. Because of these reports I concluded that " there can be changes in absorption and secretion without concomitant effects on the electric P.D." and stressed that " future investigations measuring the electrical potential should not interpret any lack of as diagnostic of the functional and change (my italics) structural integrity of the small intestine unless other tests of the organ’s absorptive and secretive functions are confirmatory ". I must leave it to others to judge whether these comments represent admittedly a cautious approach or an " opposition " to the clinical use of P.D. Surprisingly, there is more than a little similarity between my comments written five years ago and Dr Wingate’s " control of electrical studies with independent estimates of absorption will be required until we can be certain that impaired P.D. ...

Read, N. W., Holdsworth, C. D., Levin, R. J. Lancet, Sept. 14, 1974, p. 624. 2. Debnam, E. S., Levin, R. J. J. Physiol. 1972, 222, 160P. 3. Levin, R. J. in Intestinal Adaptation (edited by E. O. Riecken and R. H. Dowling); p. 125. Stuttgart, 1974. 4. Geall, M. G., Summerskill, W. H. G. Gut, 1969, 10, 418. 5. Levin, R. J. ibid. p. 868. 1.