Real time kinetics of insulin-like growth factor II (IGF-II) interaction with the IGF-II/mannose 6-phosphate receptor: the effects of domain 13 and pH

The interaction of soluble forms of the human cation-independent insulin-like growth factor-II/mannose 6-phosphate receptor (IGF-IIR) with IGFs and mannosylated ligands was analyzed in real time. IGF-IIR proteins containing domains 1-15, 10-13, 11-13, or 11-12 were combined with rat CD4 domains 3 and 4. Following transient expression in 293T cells, secreted protein was immobilized onto biosensor chips. beta-Glucuronidase and latent transforming growth factor-beta1 bound only to domains 1-15. IGF-II bound to all constructs except a control, which contained a point mutation in domain 11. The affinity of domains 1-15, 10-13, 11-13, and 11-12 to IGF-II were 14, 120, 100, and 450 nm, respectively. Our data suggest that domain 13 acts as an enhancer of IGF-II affinity by slowing the rate of dissociation, but additional enhancement by domains other than 10-13 also occurs. As the receptor functions to transport ligands from either the trans-Golgi network or extracellular space to the endosomes, the interaction of IGF-IIR extracellular domains with IGF-II was analyzed over a pH range of 5.0-7.4. The constructs behaved differently in response to pH and in recovery after low pH exposure, suggesting that pH stability of the extracellular domains depends on domains other than 10-13.

Ileal-lymphoid-nodular hyperplasia, non-specific colitis, and pervasive developmental disorder in children

BACKGROUND

We investigated a consecutive series of children with chronic enterocolitis and regressive developmental disorder.

METHODS

12 children (mean age 6 years [range 3-10], 11 boys) were referred to a paediatric gastroenterology unit with a history of normal development followed by loss of acquired skills, including language, together with diarrhoea and abdominal pain. Children underwent gastroenterological, neurological, and developmental assessment and review of developmental records. Ileocolonoscopy and biopsy sampling, magnetic-resonance imaging (MRI), electroencephalography (EEG), and lumbar puncture were done under sedation. Barium follow-through radiography was done where possible. Biochemical, haematological, and immunological profiles were examined.

FINDINGS

Onset of behavioural symptoms was associated, by the parents, with measles, mumps, and rubella vaccination in eight of the 12 children, with measles infection in one child, and otitis media in another. All 12 children had intestinal abnormalities, ranging from lymphoid nodular hyperplasia to aphthoid ulceration. Histology showed patchy chronic inflammation in the colon in 11 children and reactive ileal lymphoid hyperplasia in seven, but no granulomas. Behavioural disorders included autism (nine), disintegrative psychosis (one), and possible postviral or vaccinal encephalitis (two). There were no focal neurological abnormalities and MRI and EEG tests were normal. Abnormal laboratory results were significantly raised urinary methylmalonic acid compared with age-matched controls (p=0.003), low haemoglobin in four children, and a low serum IgA in four children.

INTERPRETATION

We identified associated gastrointestinal disease and developmental regression in a group of previously normal children, which was generally associated in time with possible environmental triggers.

Subacute combined degeneration with high serum vitamin B12 level and abnormal vitamin B12 binding protein. New cause of an old syndrome

Subacute combined degeneration of the spinal cord due to vitamin B12 deficiency invariably has been associated with a low serum vitamin B12 level. We describe a young man who presented with a unique syndrome of subacute combined degeneration associated with high serum vitamin B12 level, low red blood cell vitamin B12 level, and an abnormal plasma vitamin B12-binding protein. Uptake of cobalamin by his leukocytes in vitro was inhibited by his own but not by normal control plasma. Intensive hydroxocobalamin (vitamin B12) treatment was associated with clinical and electrophysiologic recovery accompanied by normalization of mean corpuscular volume, red blood cell vitamin B12 level, plasma homocysteine, and urinary methylmalonic acid. The subacute combined degeneration was probably precipitated by treatment with folic acid as the significance of his high serum vitamin B12 level was not apparent when he first presented with megaloblastic anemia 3 years earlier. To our knowledge, this is the first example of neurologic disease associated with high serum vitamin B12 level and provides further evidence that sometimes a serum vitamin B12 level may not be a reliable guide to vitamin B12 deficiency.

The assessment of -adrenoceptor blocking potency and cardioselectivity in vitro and in vivo

The β-adrenoceptor blocking potencies and cardioselectivities (versus tracheal smooth muscle) of propranolol, practolol and M & B 17803A have been assessed on in vitro and in vivo guinea-pig preparations. Propranolol was found to be potent but non-selective, practolol to be less potent but cardioselective. M & B 17803A resembled practolol in potency but had a more modest degree of cardioselectivity in vivo. These observations suggest that the procedures used form a simple scheme which permits a probably relevant assessment of β-adrenoceptor blocking potency and cardioselectivity.