- Email: [email protected]
E. COLI DIARRHÆA
597
glucose which apparently influenced fluid balance and gross stool output. For example, it would be interesting to know whether solid bulk in the diets varied, whether calculated fluid input included water content of solid or semisolid foods, and whether other medications were given, including Individual weight changes of the intravenous fluids. patients, which seem to have been larger than the variations in difference between intake and output, would also be of interest. Lastly, simple measurement of stool or ileostomy fluid glucose content during glucose therapy would help to confirm that glucose truly increased gross output by osmotic action as Dr. Gerson suggests. Johns Hopkins CMRT, 550 No. Broadway, DAVID R. NALIN. Baltimore, Md. 21205.
E. COLI DIARRHÆA
aLl pointed out that a large percentage of of diarrhoea are due to various serotypes of Escherichia coli, especially 0148:H28. Both 0148:H28 and 06:H16 have been shown to produce an enterotoxin which causes a diarrhceal syndrome, in the rabbit-ileal-loop model and in volunteers, resembling that of cholera.2 The loss of water and electrolytes from the intestinal mucosa can be correlated with an increase in intestinal adenyl cyclase, stimulated by E. coli or Vibrio cholera enterotoxins.3 However, the events from augmented adenyl-cyclase activity to intestinal secretion are not a complete sequence, and have only been postulated as a related series of events. We have been studying the pathogenesis of E. coli diarrhoea in the rabbit-ileal-loop model using these serotypes and others. A 16-hour broth culture of E. coli, the E. coli-free culture media, or the E. coli-free culture media concentrated to 10% of its original volume was introduced into ileal loops of the adult rabbit and response was recorded as fluid production and electrolyte fluxes. Our data show that with most serotypes of E. coli only the concentrate elicits an " excessive " outpouring of fluid from the ileal mucosa. The E. coli concentrate induces elaboration of an isotonic fluid which contains small amounts of potassium and chloride but is especially rich in sodium and bicarbonate-i.e., it is essentially similar to the response of the intestinal mucosa to cholera enterotoxin in experimental cholera. Additional work has shown that other ligated intestinal loops in the rabbit several cm. removed from the E. coliconcentrate loop respond in a like manner. This feature suggests that: (1) the E. coli concentrate is absorbed and affects the entire intestine, perhaps via the systemic circulation; or (2) the E. coli concentrate initiates an intermediate messenger which influences the entire intestinal
SIR,-Rowe
et
cases
epithelium. The testing of multiple enterotoxins from several serotypes in a single rabbit intestine can no longer be relied upon, because of their additive and perhaps synergistic effects. As a consequence, evaluation of control intestinal loops must be carried out before exposure of the intestine to E. coli enterotoxins or in separate rabbits. Our investigations also revealed that in contrast to cholera enterotoxin, where the active portion of the enterotoxin is " tightly bound " to the ileal epithelium,4 several of the E. coli enterotoxins are easily washed free. Gentle washing of ileal mucosa that is actively producing effluent in re1. 2.
Rowe, B., Taylor, J., Bettelheim, K. A. Lancet, 1970, i, 1. DuPont, H. L., Formal, S. B., Hornick, R. B., Snyder, M. J., Libonati, J. P., Sheahan, D. G., LaBrec, E. H., Kalas, J. P. New Engl. J. Med. 1971, 285, 1. 3. Evans, D. J., Jr., Chen, L. C., Curlin, G. T., Evans, D. G. Nature New Biol. 1972, 236, 137. 4. Norris, H. T., Curran, P. F., Schultz, S. G. J. infect. Dis. 1969, 119, 117.
sponse to E. coli enterotoxins
secretory
causes an
abrupt cessation of
activity.
Departments of Pathology, University of Washington School of Medicine and Veterans Administration Hospital,
Seattle, Washington, U.S.A.
T. E. STALEY H. THOMAS NORRIS J. A. S. STALEY.
OCCUPATIONAL LEAD ABSORPTION SiR,-Your comments on the report of the Windeyer Committee (Sept. 2, p. 470) are capable of misinterpretation with respect to the significance of blood-lead data and their correct use in environmental health control programmes. As far as industrial exposure to lead is concerned, the primary function of monitoring systems is to assess the efficacy of the measures to control exposure and absorption at levels which preclude the risk of damage to health. The difficulty of deciding " when absorption ends and poisoning begins " is not relevant in that context. The conclusions to be drawn from blood-lead levels in excess of 80 g. per 100 ml. are that exposure, the consequential absorption, and the related risk to health are all above the current limit of acceptability, and the fact that some lead workers are able to tolerate blood-lead levels above the threshold of 80 g. per 100 ml. without signs of ill effect should therefore be disregarded. Long experience of the blood-lead test, more particularly in the United States, attests to the reliability of accurate blood-lead data in providing essential, unequivocal information about both aspects of environmental health control
-i.e., about the conditions of exposure, and the absorption which results from them. Whatever medical action may be taken with respect to workers with excessive absorptionabove 80 µg. per 100 ml.-there is a clear need to improve the engineering control over exposure. Foresters, Colgate, Horsham, Sussex.
MORGAN H. DAVIES.
*** Reference 3 in the sixth paragraph of the editorial escaped renumbering. It applies to footnote 16.-ED. L.
CENTRAL-VENOUS-PRESSURE CANNULÆ SIR,-Iwas disturbed by Dr. Knight’s statement (Aug. 26, p. 433) that a " c.v.p. cannula should be used only for the relatively slow infusion of fluids " since in my
experience central venous pressure (c.v.p.) cannula: provide a convenient, efficient, and safe route of rapid fluid administration. A communication1 which will include detailed data substantiating this impression is in preparation, but meanwhile I should like to comment on several points. Dr. Knight is not right in claiming that an adequate flow-rate cannot be achieved. Dr. Blogg and Dr. Colvin (July 29, p. 232) demonstrated that fast infusion-rates are attainable using two recently developed cannula: available in this country, and if Dr. Knight and his fellow Australians are limited to ’ Intracaths ’ they will find that a large-size 8-inch-long (or even 12-inch rapidly shortened with sterile scissors) intracath inserted percutaneously into, e.g., the subclavian vein, via the supraclavicular 1.2 or infraclavicular3 approach, will give comparable results. A three-way tap, with side limb leading to a saline manometer set, is readily attached to such a catheter so that the c.V.P. can conveniently be read intermittently. 1. 2. 3.
Stephens, M. E. M., McMichael, H. B. Unpublished. Yoffa, D. Lancet, 1965, ii, 614. Parkinson, P. A Technique of Catheterization of the Subclavian Vein from beneath the Clavicle. London, 1972.
glucose which apparently influenced fluid balance and gross stool output. For example, it would be interesting to know whether solid bulk in the diets varied, whether calculated fluid input included water content of solid or semisolid foods, and whether other medications were given, including Individual weight changes of the intravenous fluids. patients, which seem to have been larger than the variations in difference between intake and output, would also be of interest. Lastly, simple measurement of stool or ileostomy fluid glucose content during glucose therapy would help to confirm that glucose truly increased gross output by osmotic action as Dr. Gerson suggests. Johns Hopkins CMRT, 550 No. Broadway, DAVID R. NALIN. Baltimore, Md. 21205.
E. COLI DIARRHÆA
aLl pointed out that a large percentage of of diarrhoea are due to various serotypes of Escherichia coli, especially 0148:H28. Both 0148:H28 and 06:H16 have been shown to produce an enterotoxin which causes a diarrhceal syndrome, in the rabbit-ileal-loop model and in volunteers, resembling that of cholera.2 The loss of water and electrolytes from the intestinal mucosa can be correlated with an increase in intestinal adenyl cyclase, stimulated by E. coli or Vibrio cholera enterotoxins.3 However, the events from augmented adenyl-cyclase activity to intestinal secretion are not a complete sequence, and have only been postulated as a related series of events. We have been studying the pathogenesis of E. coli diarrhoea in the rabbit-ileal-loop model using these serotypes and others. A 16-hour broth culture of E. coli, the E. coli-free culture media, or the E. coli-free culture media concentrated to 10% of its original volume was introduced into ileal loops of the adult rabbit and response was recorded as fluid production and electrolyte fluxes. Our data show that with most serotypes of E. coli only the concentrate elicits an " excessive " outpouring of fluid from the ileal mucosa. The E. coli concentrate induces elaboration of an isotonic fluid which contains small amounts of potassium and chloride but is especially rich in sodium and bicarbonate-i.e., it is essentially similar to the response of the intestinal mucosa to cholera enterotoxin in experimental cholera. Additional work has shown that other ligated intestinal loops in the rabbit several cm. removed from the E. coliconcentrate loop respond in a like manner. This feature suggests that: (1) the E. coli concentrate is absorbed and affects the entire intestine, perhaps via the systemic circulation; or (2) the E. coli concentrate initiates an intermediate messenger which influences the entire intestinal
SIR,-Rowe
et
cases
epithelium. The testing of multiple enterotoxins from several serotypes in a single rabbit intestine can no longer be relied upon, because of their additive and perhaps synergistic effects. As a consequence, evaluation of control intestinal loops must be carried out before exposure of the intestine to E. coli enterotoxins or in separate rabbits. Our investigations also revealed that in contrast to cholera enterotoxin, where the active portion of the enterotoxin is " tightly bound " to the ileal epithelium,4 several of the E. coli enterotoxins are easily washed free. Gentle washing of ileal mucosa that is actively producing effluent in re1. 2.
Rowe, B., Taylor, J., Bettelheim, K. A. Lancet, 1970, i, 1. DuPont, H. L., Formal, S. B., Hornick, R. B., Snyder, M. J., Libonati, J. P., Sheahan, D. G., LaBrec, E. H., Kalas, J. P. New Engl. J. Med. 1971, 285, 1. 3. Evans, D. J., Jr., Chen, L. C., Curlin, G. T., Evans, D. G. Nature New Biol. 1972, 236, 137. 4. Norris, H. T., Curran, P. F., Schultz, S. G. J. infect. Dis. 1969, 119, 117.
sponse to E. coli enterotoxins
secretory
causes an
abrupt cessation of
activity.
Departments of Pathology, University of Washington School of Medicine and Veterans Administration Hospital,
Seattle, Washington, U.S.A.
T. E. STALEY H. THOMAS NORRIS J. A. S. STALEY.
OCCUPATIONAL LEAD ABSORPTION SiR,-Your comments on the report of the Windeyer Committee (Sept. 2, p. 470) are capable of misinterpretation with respect to the significance of blood-lead data and their correct use in environmental health control programmes. As far as industrial exposure to lead is concerned, the primary function of monitoring systems is to assess the efficacy of the measures to control exposure and absorption at levels which preclude the risk of damage to health. The difficulty of deciding " when absorption ends and poisoning begins " is not relevant in that context. The conclusions to be drawn from blood-lead levels in excess of 80 g. per 100 ml. are that exposure, the consequential absorption, and the related risk to health are all above the current limit of acceptability, and the fact that some lead workers are able to tolerate blood-lead levels above the threshold of 80 g. per 100 ml. without signs of ill effect should therefore be disregarded. Long experience of the blood-lead test, more particularly in the United States, attests to the reliability of accurate blood-lead data in providing essential, unequivocal information about both aspects of environmental health control
-i.e., about the conditions of exposure, and the absorption which results from them. Whatever medical action may be taken with respect to workers with excessive absorptionabove 80 µg. per 100 ml.-there is a clear need to improve the engineering control over exposure. Foresters, Colgate, Horsham, Sussex.
MORGAN H. DAVIES.
*** Reference 3 in the sixth paragraph of the editorial escaped renumbering. It applies to footnote 16.-ED. L.
CENTRAL-VENOUS-PRESSURE CANNULÆ SIR,-Iwas disturbed by Dr. Knight’s statement (Aug. 26, p. 433) that a " c.v.p. cannula should be used only for the relatively slow infusion of fluids " since in my
experience central venous pressure (c.v.p.) cannula: provide a convenient, efficient, and safe route of rapid fluid administration. A communication1 which will include detailed data substantiating this impression is in preparation, but meanwhile I should like to comment on several points. Dr. Knight is not right in claiming that an adequate flow-rate cannot be achieved. Dr. Blogg and Dr. Colvin (July 29, p. 232) demonstrated that fast infusion-rates are attainable using two recently developed cannula: available in this country, and if Dr. Knight and his fellow Australians are limited to ’ Intracaths ’ they will find that a large-size 8-inch-long (or even 12-inch rapidly shortened with sterile scissors) intracath inserted percutaneously into, e.g., the subclavian vein, via the supraclavicular 1.2 or infraclavicular3 approach, will give comparable results. A three-way tap, with side limb leading to a saline manometer set, is readily attached to such a catheter so that the c.V.P. can conveniently be read intermittently. 1. 2. 3.
Stephens, M. E. M., McMichael, H. B. Unpublished. Yoffa, D. Lancet, 1965, ii, 614. Parkinson, P. A Technique of Catheterization of the Subclavian Vein from beneath the Clavicle. London, 1972.