Enzyme activities in the blood of infants and adults

Prolonged Apnoea Following E.C.T. Modified by Suxethonium (Brevidil “E”)

There have been numerous reports in recent years of prolonged apnoea resulting from the use of suxamethonium (succinylcholine, “Scoline”) in general anaesthesia and for electroplexy. For example, Grant (16) described a case of respiratory paralysis lasting 2 to 3 post-operative days following an intravenous dose of 80 mg. of suxamethonium, and Cowan (7) reported a patient who underwent a partial gastrectomy and exhibited complete apnoea for 9 hours duration after only 25 mg. of suxamethonium had been given, and who subsequently died. Hurley and Monro (22) reported apnoea lasting for 10 minutes following 20 mg. of suxamethonium used as a relaxant for electroplexy, and for 20 minutes after decamethonium iodide.

Muscarinic cholinergic receptors and acetylcholinesterase activity in umbilical artery and vein in pregnancy-induced hypertension (pre-eclampsia)

The influence of pregnancy-induced hypertension (pre-eclampsia) on muscarinic cholinergic receptors and on acetylcholinesterase (AChE) activity was investigated using frozen sections of the umbilical artery and vein. Pre-eclamptic patients undergoing Caesarean delivery and normotensive pregnant control woman undergoing Caesarean delivery with similar parity, gestation length and age were examined. Muscarinic cholinergic receptors were assayed in frozen sections of the umbilical artery and vein by a radioligand binding assay technique, using [3H]-N-methyl scopolamine (NMS) as a ligand. AChE was demonstrated with a histochemical technique associated with microdensitometry. [3H]-NMS was specifically bound to sections of both umbilical artery and vein in a manner consistent with the labelling of muscarinic cholinergic receptors. The affinity of the radioligand was similar in the two vessels, whereas the maximum density of binding sites (Bmax) was higher in the umbilical vein than in the artery. A faint AChE reactivity was observed in the tunica media of both umbilical artery and vein. In pre-eclampsia, a loss of [3H]-NMS binding sites not accompanied by changes in the affinity of radioligand was found. The decrease of muscarinic cholinergic receptors involved to a greater extent the umbilical artery than the vein. No differences in AChE activity were found at the level of umbilical artery and vein between control and pre-eclamptic subjects. These findings suggest that pre-eclampsia is characterized by a loss of muscarinic cholinergic receptors in the umbilical circulation not accompanied by changes of the acetylcholine catabolizing enzyme AChE. It is possible that the decreased density of vascular muscarinic cholinergic receptors in pregnancy-induced hypertension contribute to the increased resistance of the umbilical circulation occurring in pre-eclampsia.

The Bessis reticular cell, the hemoglobin 'switch' and the role of fetal hemoglobin: a hypothesis

With the help of diverse factors, definitive erythropoiesis is induced by the junction of a pluripotential stem-cell with a specialized macrophage. In the normal adult marrow the latter becomes the reticular cell forming the core of an 'erythroblastic island'. It stays in close contact with all the erythroid cells descending from the stem-cell until their full maturation. While this contact lasts, only alpha and beta (delta) globin chains are produced. The production of gamma chains is inhibited. Stress forces the reticular cell to let the erythroid cells go. The stronger the stress, the earlier the separation. When free from the reticular cell, the erythroid cells stop producing beta chains and switch to form gamma ones. Increase in the volume of blood circulation is a potent stress. Since it is relatively enormous in the embryo and the fetus, most hemoglobin produced at these periods will be fatal. The important quality of fetal hemoglobin is its high oxidizability. It permits the senescent fetal red cell to be hemolysed intravascularly before any membrane alterations appear. The heme is dealt with by the placenta. Since no erythrophagocytosis has occurred, no bilirubin is formed. This process prevents bilirubin, which is toxic to the fetal liver, to reach it.

Acetylcholine output and foetal vascular resistance of human perfused placental cotyleda

The foetal villous vessels of single cotyleda of human placentae have been perfused with a constant flow of Krebs solution, recording inflow pressure and passing the venous perfusate in cascade over guinea-pig ileum and rat stomach strip preparations in vitro. Each cotyledon released for at least 4 h a substance that was probably acetylcholine. The perfusate caused contractions of both preparations which were inhibited by atropine or hyoscine and potentiated by physostigmine. Contractile activity was destroyed after incubation at 37 degrees C of perfusate with acetylcholinesterase but not with acetylcholinesterase plus physostigmine. When the perfusion temperature was lowered to 34 degrees C or below, acetylcholine output was reduced, the extent depending on the fall in temperature. No change in resistance of the villous vessels occurred during the changes in temperature or in the presence at 37 degrees C of atropine, hyoscine, hexamethonium, (+)-tubocurarine, hemicholinium-3 or bretylium. Submaximal vasoconstrictor responses of the villous vessels to the thromboxane A2-mimetic U46619 were not affected by reduction of the perfusion temperature to 30 degrees C, which lowered acetylcholine-like output by approximately 70%. Responses to U46619, at 37 degrees C, were unchanged during the presence of atropine or hyoscine. Acetylcholine is released into the foetal circulation of the human placenta but no evidence could be obtained that it affects villous vascular smooth muscle tone or vasoconstrictor responses.

Reference values for erythrocyte acetylcholinesterase and plasma cholinesterase activities in children, implications for organophosphate intoxication

Acetylcholinesterase and cholinesterase activity was measured in the blood of both healthy children 0-12 years of age and adults by a recently developed radiochemical method. Children less than 4 months of age were found to have lower levels for these enzymes than adults. Above this age, however, similar values were obtained for children and adults. A case report of an organophosphate intoxication is presented and is discussed in the light of our results.

5-oxoprolinuria: biochemical observations and case report

We have studied a patient with 5-oxoprolinuria who presented with hemolysis and metabolic acidosis as a neonate; he has had normal growth and development to one year of age. Compensated hemolytic anemia persists, and he requires alkalinizing agents for correction of acidosis. Biochemical studies have confirmed that a deficiency of glutathione synthetase is responsible for the 5-oxoprolinuria. Genetic heterogeneity was apparent on comparative study of glutathione synthetase kinetics in cells from two patients with this disorder. The consequences of the deficiency of glutathione synthetase, decreased intracellular glutathione, and overproduction of 5-oxoproline are discussed with reference to the possible cellular roles of these compounds.

Developmental changes in purine phosphoribosyltransferases in human and rat tissues

1. The hypoxanthine/guanine and adenine phosphoribosyltransferase activities in a wide variety of human tissues were studied during their growth and development from foetal life onward. A wide range of activities develop after birth, with especially high values in the central nervous system and testes. 2. Postnatal development of hypoxanthine/guanine phosphoribosyltransferase was also defined in the rat. Although there were increases in the central nervous system and testes, there was also a rise in activity in the liver, which was less marked in man. 3. A sensitive radiochemical assay method, using dTTP to inhibit 5'-nucleotidase activity, suitable for tissue extracts, was developed. 4. No definite evidence of the existence of tissue-specific isoenzymes of hypoxanthine/guanine or adenine phosphoribosyltransferase was found. Hypoxanthine/guanine phosphoribosyltransferase in testes, however, had a significantly different thermal-denaturation rate constant. 5. The findings are discussed in an attempt to relate activity of hypoxanthine/guanine phosphoribosyltransferase to biological function. Growth as well as some developmental changes appear to be related to increase in the activity of this enzyme.

Disorders of the red cell membrane: a review of biochemical and physiologic alterations of erythrocyte membranes which may lead to morphologic changes and shortened cell survival

Morphologically similar cells can be seen in such varied conditions as liver disease, renal disease, a-betalipoproteinemia, malab sorption states, congenital nonspherocytic anemias, thalassemia, iron deficiency, pykno cytosis, hemolytic-uremic syndrome, erythro cyte enzyme deficiencies, etc.

The common denominator in these condi tions may be an increase in membrane rigid ity, resulting from a diversity of causes. These would include altered protein-lipid- carbohydrate composition, abnormally struc tured hemoglobins, the presence of Heinz bodies due to altered glycolysis or unstable hemoglobins. The end result of such altered membrane elasticity, regardless of cause, would be fragmentation and destruction of the red cells during passage through small vascular channels, particularly in the spleen. Changes in erythrocyte stromal composi tion often seem to reflect more generalized systemic metabolic disorders. Whether any of the alterations of membrane composition are causally related to either the morpho logic changes or the shortened cell survival still remains to be proven.

Haemoglobin and red cell enzyme changes in juvenile myeloid leukaemia

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Foetal physiology and child health

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