SUMMARY1. The preparation of a hormone-binding protein fraction (neurophysin) from porcine neurohypophyses is described.2. It was shown by gel-filtration that the protein (which sedimented as a single component on analytical ultracentrifugation) forms complexes with oxytocin and lysine vasopressin. The maximum capacity of porcine neurophysin to bind oxytocin and lysine vasopressin was estimated from the results of dialysis experiments as 232 u. oxytocin and 48 u. lysine vasopressin/mg protein.3. Binding of oxytocin and lysine vasopressin by neurophysin was completely inhibited in the presence of calcium in concentrations greater than 106 M but is unaffected at less than 10-7 m-Ca. The concentration of calcium required to inhibit binding did not appear to be dependent on hormone or protein concentrations.4. No evidence was obtained that calcium was bound by neurophysin or by the peptide hormones either alone or in combination.5. These results are discussed in the light of the hypothesis that release of the hormone from the neurohypophysis is mediated by calcium.

BackgroundAcute intermittent porphyria is a rare autosomal dominant disorder caused by a deficiency of the enzyme, hydroxymethylbilane synthase. Recognition of acute neurovisceral attacks can be difficult due to the nonspecific nature of symptoms.Case presentationWe report a case of 33-year-old male patient who presented with recurrent episodes of severe abdominal pain, nausea, vomiting, constipation and numbness of bilateral lower limb extremities. These nonspecific neurovisceral attacks were subject to medical and surgical misdiagnoses of acute appendicitis, sinus tachycardia, renal calculi, drug-induced acute interstitial nephritis and two episodes of partial intestinal obstruction. The sixth acute attack raised the suspicion of an acute porphyria. Watson and Schwartz test was positive for porphobilinogen in urine. Mutation analysis by DNA sequencing of the extracted DNA of the proband revealed a previously reported missense mutation, c.517C>T encoding p.R173W in the HMBS gene, confirming the diagnosis of Acute Intermittent Porphyria. Four out of five family members who underwent targeted mutation analyses were mutation-positive.ConclusionThe most common clinical presentation of Acute Intermittent Porphyria is abdominal pain with neurovisceral manifestations which are common to several medical, psychiatric and surgical pathologies. This leads to underdiagnosis and misdiagnosis of this disorder, incorrect management, and severe complications. Therefore, a high index of suspicion and awareness of front line laboratory investigations are important for diagnosis. Definitive diagnosis enables implementation of strategies to prevent acute attacks, and also triggers genetic testing and genetic counseling of at-risk family members.

BackgroundUric acid is the metabolic end product of purine metabolism in humans. Altered serum and urine uric acid level (both above and below the reference ranges) is an indispensable marker in detecting rare inborn errors of metabolism. We describe different case scenarios of 4 Sri Lankan patients related to abnormal uric acid levels in blood and urine.Case 1A one-and-half-year-old boy was investigated for haematuria and a calculus in the bladder. Xanthine crystals were seen in microscopic examination of urine sediment. Low uric acid concentrations in serum and low urinary fractional excretion of uric acid associated with high urinary excretion of xanthine and hypoxanthine were compatible with xanthine oxidase deficiency.Case 2An 8-month-old boy presented with intractable seizures, feeding difficulties, screaming episodes, microcephaly, facial dysmorphism and severe neuro developmental delay. Low uric acid level in serum, low fractional excretion of uric acid and radiological findings were consistent with possible molybdenum cofactor deficiency. Diagnosis was confirmed by elevated levels of xanthine, hypoxanthine and sulfocysteine levels in urine.Case 3A 3-year-10-month-old boy presented with global developmental delay, failure to thrive, dystonia and self-destructive behaviour. High uric acid levels in serum, increased fractional excretion of uric acid and absent hypoxanthine–guanine phosphoribosyltransferase enzyme level confirmed the diagnosis of Lesch–Nyhan syndrome.Case 4A 9-year-old boy was investigated for lower abdominal pain, gross haematuria and right renal calculus. Low uric acid level in serum and increased fractional excretion of uric acid pointed towards hereditary renal hypouricaemia which was confirmed by genetic studies.ConclusionAbnormal uric acid level in blood and urine is a valuable tool in screening for clinical conditions related to derangement of the nucleic acid metabolic pathway.

1. Antiserum was raised in rabbits to neurophysin prepared from posterior pituitaries of pigs. The presence of antibody reacting with porcine neurophysin was demonstrated in precipitation, gel diffusion and immunoelectrophoretic tests. 2. The antibody was species specific and did not react with protein from rat, bovine or guinea‐pig neurohypophyses. 3. The occurrence of antigen reacting with anti‐neurophysin serum was demonstrated in acetic acid extracts of porcine kidney but there was no evidence for the presence of antigen in extracts of liver or spleen prepared in the same way. 4. Protein fractions (‘N‐fractions’) from various organs and tissues of pigs were obtained by the same methods used to prepare neurophysin from posterior pituitaries and were tested for antigenicity in reaction with neurophysin antibody. N‐fractions from kidney, uterus, mammary gland and serum contained antigen while fractions from liver, spleen, brain and skeletal muscle did not react with the anti‐neurophysin serum.

SUMMARY1. Protein fractions were prepared from serum and various organs of pigs following the methods used to extract and purify neurophysin from posterior pituitaries.2. Protein fractions extracted from porcine kidney, uterus, mammary gland or serum, which contain antigen reacting with anti-neurophysin serum, form non-dialysable complexes with oxytocin and/or lysine vasopressin.3. Protein from uterus or mammary gland bound oxytocin but not lysine vasopressin, while protein extracted from kidney bound lysine vasopressin but not oxytocin: protein from serum bound both hormones.4. Protein fractions prepared in the same way from porcine liver, spleen, skeletal muscle and brain, which do not contain antigen reacting with antineurophysin serum, did not form complexes with neurohypophysial hormone.5. The formation of complexes between the renal or uterine protein fractions and lysine vasopressin or oxytocin is inhibited by the addition of 1.0 x 10-6 M-CaCl2.6. I-Desamino 8-arginine vasopressin is not bound by neurophysin prepared from porcine posterior pituitaries or the protein from porcine kidneys, while 8-arginine vasopressin does form non-dialysable complexes with proteins from both sources. 7. A protein fraction extracted from guinea-pig kidney by similar preparative methods also bound lysine vasopressin and the binding was inhibited by addition of CaCl2.