492
Cyanate derived from
urea
in uraemia
SIR,-Dr Lee and colleagues (Dec 7, p 1438) propose that urea itself is the cause of tissue damage in chronic renal failure by perhaps acting to destabilise proteins, and they point out that methylamine derivatives can counteract this effect. They also suggest that methylamine derivatives may protect proteins against urea in renal failure patients, which is something they seem to do in cartilaginous fish. It may be worthwhile considering an addition to this fascinating hypothesis, and that is a possible role for cyanate. Urea under physiological conditions comes to equilibrium with cyanate’—or strictly speaking, isocyanate. Cyanate can react with amino and thiol groups of proteins to destabilise them.2,3 It inhibits several enzymes and interferes with membrane junctions.2,4 Cyanate may have a role in cataract formation. Renal failure and severe diarrhoea are risk factors for cataract, and these links may be partly through cyanate, although osmotic shock and urea may play their part.’ Lee and colleagues’ proposed protective effect of methylamine derivatives against urea would apply equally well against cyanate since the amines would merely react with cyanate to detoxify it. Thus the sharks that Lee et al discuss may have the amines to mop up the cyanate as well as to counteract the destabilising effect of urea. Nuffield Laboratory of University of Oxford, Oxford OX2 6AW, UK
Ophthalmology,
J. J. HARDING
1. Dimhuber P, Schütz F. The isomenc transformation of urea into ammonium sulphate m aqueous solutions. Biochem J 1948; 42: 628-32. 2. Harding JJ. Nonenzymic covalent post-translational modification of proteins in vivo. Adv Protein Chem 1985; 37: 247-334. 3. Beswick HT, Harding JJ. Conformational changes induced m bovine lens &agr;-crystallin by carbamylation: relevance to cataract. Biochem J 1984; 223: 221-27. 4. Croghan PC, Duncan G, Emptage NJ Aspirin prevents recovery of CO2-induced change of internal resistance in the isolated lens of the frog Rana pipiens J Physiol
1988; 396: 49P. 5. Harding JJ. Cataract: biochemistry, epidemiology and pharmacology. London Chapman and Hall, 1991.
Latex allergy in
Chylous output
in patient 1
(upper)
and
patient 2 (lower).
TPN =total parenteral nutrition
postoperative day, when he was orally fed, a milky lymphorrhagia (triglyceride concentration 110 mg/dl) appeared from the drain site (more than 5 1 daily) (figure, upper). Total parenteral nutrition (TPN) with complete bowel rest was initiated but lymph flow still fluctuated between 2000 ml and 3000 ml daily. Octreotide was subcutaneously injected (3x0-1mg per day) for 2 weeks, inducinga slight decrease of lymph output. Lymphorrhagia subsequently stopped abruptly while the patient was still on TPN. Patient 2-A 42-year-old woman had right lower lobectomy for lymphangiomatosis. During operation, lymph was drained, but lymphorrhagia persisted after surgery (figure, lower). Initiation of TPN combined with subcutaneous octreotide substantially reduced the lymph flow, although this did not stop it completely. 1 week later octreotide was replaced by intravenous somatostatin (2 x 3 mg daily) but the lymph output levelled off between 500 ml and 1000 ml daily. Discontinuation of somatostatin did not produce an increase in lymph output. Finally, lymphorrhagia decreased spontaneously on day 32 of TPN. In these two patients, complete bowel rest and TPN greatly reduced lymph flow but no complementary effect was seen when somatostatin or its analogue were administered. Departments of Gastroenterology and Thoracic Surgery, Hôpital Erasme, 1070 Brussels, Belgium 1. Milson
A. VAN GOSSUM C. STEFANIDIS Ph. DE FRANQUEN
J, et al. Chylothorax: an assessment of current surgical management. Thorac Cardiovasc Surg 1985; 89: 221-27. 2. Ulibarri J, Sanz Y, Fuentes C, Mancha A, Aramendia M, Sánchez S. Reduction of lymphorrhagia from ruptured thoracic duct by somatostatin. Lancet 1990; 336: 258. 3. Di Constanzo J, Cano N, Martin J. Somatostatin in persistent gastrointestinal fistula treated by TPN. Lancet 1982; ii: 338-39.
patient with allergy to fruit
SiR,—Hypersensidvity reactions to latex are well recognised and the risk of anaphylaxis during delivery, surgery, or medical examinations makes essential the identification of latex-allergic patients. Allergy to latex proteins has been demonstrated by immunological techniques, such as immunoblotting, and Turjanma et all isolated two major antigenic constituents, with molecular weights around 10 kDa. Occasionally, this allergy is associated with allergy to fruit/.3 and it predominates in atopic individuals.4,s3 Crossreactivity between banana and latex has been demonstrated, and a common epitope is suspected. We report here a case of recurrent anaphylactic reactions during cystoscopy, all related to latex, in a patient with a pre-existing allergy to banana and avocado. A 67-year-old man had surgical resection for bladder carcinoma in 1987. Subsequently, cystoscopy under general anaesthesia was done without any trouble. He reported chronic sinusitis but had no history of allergy. Nevertheless, there was a history of atopy in his family. In 1988 he started to have allergy to bananas, with collapse and urticaria 10 minutes after eating this fruit; he recovered quickly when adrenaline and steroids were injected. Three less severe collapses were observed in the ensuing months, all related to banana. After that he avoided this fruit. In November, 1989, he collapsed with bronchospasm after a soup containing carrots, potatoes, parsley, and avocado. Skin prick-tests were positive to banana (+ +) and avocado (+ +) and negative for the other nutriments. A radioallergosorbent test (RAST) was also positive to banana and to avocado. Avoidance of the incriminated vegetables and the use of antihistamines was recommended. 3 hours after cystoscopy in March, 1990, he progressively collapsed (blood pressure 60/40 mm Hg), with asthenia, general malaise, and nausea but no skin reaction. The symptoms were rapidly relieved with a corticosteroid and an adrenaline infusion. At a check-up 3 weeks later a positive skin prick-test with latex (+ + +) was noted and an RAST to this allergen was positive. The test remained negative for muscle relaxants, gelatin, hypnotics, and benzodiazepines. Latex surgical gloves were suspected but a subsequent cystoscopy with latex-free gloves but a latex catheter
Cyanate derived from
urea
in uraemia
SIR,-Dr Lee and colleagues (Dec 7, p 1438) propose that urea itself is the cause of tissue damage in chronic renal failure by perhaps acting to destabilise proteins, and they point out that methylamine derivatives can counteract this effect. They also suggest that methylamine derivatives may protect proteins against urea in renal failure patients, which is something they seem to do in cartilaginous fish. It may be worthwhile considering an addition to this fascinating hypothesis, and that is a possible role for cyanate. Urea under physiological conditions comes to equilibrium with cyanate’—or strictly speaking, isocyanate. Cyanate can react with amino and thiol groups of proteins to destabilise them.2,3 It inhibits several enzymes and interferes with membrane junctions.2,4 Cyanate may have a role in cataract formation. Renal failure and severe diarrhoea are risk factors for cataract, and these links may be partly through cyanate, although osmotic shock and urea may play their part.’ Lee and colleagues’ proposed protective effect of methylamine derivatives against urea would apply equally well against cyanate since the amines would merely react with cyanate to detoxify it. Thus the sharks that Lee et al discuss may have the amines to mop up the cyanate as well as to counteract the destabilising effect of urea. Nuffield Laboratory of University of Oxford, Oxford OX2 6AW, UK
Ophthalmology,
J. J. HARDING
1. Dimhuber P, Schütz F. The isomenc transformation of urea into ammonium sulphate m aqueous solutions. Biochem J 1948; 42: 628-32. 2. Harding JJ. Nonenzymic covalent post-translational modification of proteins in vivo. Adv Protein Chem 1985; 37: 247-334. 3. Beswick HT, Harding JJ. Conformational changes induced m bovine lens &agr;-crystallin by carbamylation: relevance to cataract. Biochem J 1984; 223: 221-27. 4. Croghan PC, Duncan G, Emptage NJ Aspirin prevents recovery of CO2-induced change of internal resistance in the isolated lens of the frog Rana pipiens J Physiol
1988; 396: 49P. 5. Harding JJ. Cataract: biochemistry, epidemiology and pharmacology. London Chapman and Hall, 1991.
Latex allergy in
Chylous output
in patient 1
(upper)
and
patient 2 (lower).
TPN =total parenteral nutrition
postoperative day, when he was orally fed, a milky lymphorrhagia (triglyceride concentration 110 mg/dl) appeared from the drain site (more than 5 1 daily) (figure, upper). Total parenteral nutrition (TPN) with complete bowel rest was initiated but lymph flow still fluctuated between 2000 ml and 3000 ml daily. Octreotide was subcutaneously injected (3x0-1mg per day) for 2 weeks, inducinga slight decrease of lymph output. Lymphorrhagia subsequently stopped abruptly while the patient was still on TPN. Patient 2-A 42-year-old woman had right lower lobectomy for lymphangiomatosis. During operation, lymph was drained, but lymphorrhagia persisted after surgery (figure, lower). Initiation of TPN combined with subcutaneous octreotide substantially reduced the lymph flow, although this did not stop it completely. 1 week later octreotide was replaced by intravenous somatostatin (2 x 3 mg daily) but the lymph output levelled off between 500 ml and 1000 ml daily. Discontinuation of somatostatin did not produce an increase in lymph output. Finally, lymphorrhagia decreased spontaneously on day 32 of TPN. In these two patients, complete bowel rest and TPN greatly reduced lymph flow but no complementary effect was seen when somatostatin or its analogue were administered. Departments of Gastroenterology and Thoracic Surgery, Hôpital Erasme, 1070 Brussels, Belgium 1. Milson
A. VAN GOSSUM C. STEFANIDIS Ph. DE FRANQUEN
J, et al. Chylothorax: an assessment of current surgical management. Thorac Cardiovasc Surg 1985; 89: 221-27. 2. Ulibarri J, Sanz Y, Fuentes C, Mancha A, Aramendia M, Sánchez S. Reduction of lymphorrhagia from ruptured thoracic duct by somatostatin. Lancet 1990; 336: 258. 3. Di Constanzo J, Cano N, Martin J. Somatostatin in persistent gastrointestinal fistula treated by TPN. Lancet 1982; ii: 338-39.
patient with allergy to fruit
SiR,—Hypersensidvity reactions to latex are well recognised and the risk of anaphylaxis during delivery, surgery, or medical examinations makes essential the identification of latex-allergic patients. Allergy to latex proteins has been demonstrated by immunological techniques, such as immunoblotting, and Turjanma et all isolated two major antigenic constituents, with molecular weights around 10 kDa. Occasionally, this allergy is associated with allergy to fruit/.3 and it predominates in atopic individuals.4,s3 Crossreactivity between banana and latex has been demonstrated, and a common epitope is suspected. We report here a case of recurrent anaphylactic reactions during cystoscopy, all related to latex, in a patient with a pre-existing allergy to banana and avocado. A 67-year-old man had surgical resection for bladder carcinoma in 1987. Subsequently, cystoscopy under general anaesthesia was done without any trouble. He reported chronic sinusitis but had no history of allergy. Nevertheless, there was a history of atopy in his family. In 1988 he started to have allergy to bananas, with collapse and urticaria 10 minutes after eating this fruit; he recovered quickly when adrenaline and steroids were injected. Three less severe collapses were observed in the ensuing months, all related to banana. After that he avoided this fruit. In November, 1989, he collapsed with bronchospasm after a soup containing carrots, potatoes, parsley, and avocado. Skin prick-tests were positive to banana (+ +) and avocado (+ +) and negative for the other nutriments. A radioallergosorbent test (RAST) was also positive to banana and to avocado. Avoidance of the incriminated vegetables and the use of antihistamines was recommended. 3 hours after cystoscopy in March, 1990, he progressively collapsed (blood pressure 60/40 mm Hg), with asthenia, general malaise, and nausea but no skin reaction. The symptoms were rapidly relieved with a corticosteroid and an adrenaline infusion. At a check-up 3 weeks later a positive skin prick-test with latex (+ + +) was noted and an RAST to this allergen was positive. The test remained negative for muscle relaxants, gelatin, hypnotics, and benzodiazepines. Latex surgical gloves were suspected but a subsequent cystoscopy with latex-free gloves but a latex catheter
