The porphyrias are disorders of haem biosynthesis which present with acute neurovisceral attacks or disorders of sun-exposed skin. Acute attacks occur mainly in adults and comprise severe abdominal pain, nausea, vomiting, autonomic disturbance, central nervous system involvement and peripheral motor neuropathy. Cutaneous porphyrias can be acute or chronic presenting at various ages. Timely diagnosis depends on clinical suspicion leading to referral of appropriate samples for screening by reliable biochemical methods. All samples should be protected from light. Investigation for an acute attack: • Porphobilinogen (PBG) quantitation in a random urine sample collected during symptoms. Urine concentration must be assessed by measuring creatinine, and a repeat requested if urine creatinine <2 mmol/L. • Urgent porphobilinogen testing should be available within 24 h of sample receipt at the local laboratory. Urine porphyrin excretion (TUP) should subsequently be measured on this urine. • Urine porphobilinogen should be measured using a validated quantitative ion-exchange resin-based method or LC-MS. • Increased urine porphobilinogen excretion requires confirmatory testing and clinical advice from the National Acute Porphyria Service. • Identification of individual acute porphyrias requires analysis of urine, plasma and faecal porphyrins. Investigation for cutaneous porphyria: • An EDTA blood sample for plasma porphyrin fluorescence emission spectroscopy and random urine sample for TUP. • Whole blood for porphyrin analysis is essential to identify protoporphyria. • Faeces need only be collected, if first-line tests are positive or if clinical symptoms persist. Investigation for latent porphyria or family history: • Contact a specialist porphyria laboratory for advice. Clinical, family details are usually required.

at higher angles indicate about 10% expansion of the calculated values compared with the observed one. Further, about 4% expansion may be expected 13 from the orbital moment since ^ = 2.30. We believe the above-mentioned expansion of the calculated form factor would be attributed to the approximate nature of the Hartree-Fock atomic wave functions. It should be noted that even in an ionic crystal such as K 2 CuF 4 , covalency effect on the form factor is quite large and one tends to overlook such an effect with the use of conventional Bragg scattering technique.The phase-separation phenomenon in the Ising model of ferromagnetism with dimensionality d = 2, 3 has recently been investigated. It has been shown 102 that symmetry-breaking boundary conditions can induce phase separation with an associated surface tension.Gallavotti 3 then demonstrated that the interface for d = 2 is very diffuse, unlike the situation for d = 3, where the interface was shown by Dobrushin 4 to be localized. These results were obtained for 0« T

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Circulating NE is higher in painful than painless diabetic neuropathy. We suggest that painful neuropathy is associated with a relatively higher number of functioning sympathetic fibers that may contribute to pain.