Separation of three isoenzymes of N-acetyl-beta-D-hexosaminidase from human tissues by cellulose acetate membrane electrophoresis.

The separation of N-acetyl-beta-D-hexosaminidase isoenzymes from human tissues is used in the diagnosis and differential diagnosis of GM(2) gangliosidosis, since in type 1 the A isoenzyme is deficient and in type 2 both the A and B isoenzymes are deficient. Peripheral blood leucocytes are commonly used for these investigations, and the present study demonstrates that, in addition to these two isoenzymes, a third isoenzyme can be separated from leucocytes by cellulose acetate membrane electrophoresis. This isoenzyme is more anodic than the A and B isoenzymes and is similar to the hexosaminidase C isoenzyme recently reported in embryonic tissue extracts. The isoenzyme was also clearly demonstrable in human liver and kidney but was present in much lower concentrations in cultured cells. It could be demonstrated in leucocytes even after prolonged storage at -20 degrees , and, like the A isoenzyme, is partially inactivated by a short exposure to heat.

The significance of variation in the selectivity of proteinuria.

The selectivity of proteinuria has been determined immunochemically at least 4 times over periods of 3 years or more in 27 children and adolescents who had been investigated by renal biopsy. Variations of the selectivity outside the limits of experimental error were observed in 14 patients, in 8 of whom there was a progressive decline. Six of these 8 had focal and segmental glomerular lesions, including one case of Alport's syndrome, and 2 had proliferative glomerulonephritis. Two different anomalies of relative IgG clearance were noted: in proliferative glomerulonephritis there was a constantly low clearance, and in focal glomerulosclerosis an elevated clearance increasing with time. Indirect evidence suggests that the latter may be due to the presence of low molecular weight IgG fragments in serum and urine.

Immunoelectrophoretic study of proteins in middle ear effusion. A study of secretory otitis media in children.

An immunoelectrophoretic study of the proteins of middle ear effusions in children with secretory otitis media is described. The findings support the view that the effusion is an exudate as a result of mucosal reaction. The protein content of the fluid appears to decrease as the condition becomes more chronic, and this seems to be enhanced by antibiotic treatment. In cases of bilateral disease, the ears may be in a quite different pathological phase, thus each ear should be treated independently.

Heterozygote detection in phenylketonuria. Measurement of discriminatory ability and interpretation of the phenylalanine loading test by determination of the heterozygote likelihood ratio.

Two tests of heterozygosity for phenylketonuria, the phenylalanine/tyrosine ratio in the plasma after a fast and the response to an oral load of phenylalanine, have been compared in obligate heterozygotes for phenylketonuria and apparent normal homozygotes. The discriminatory ability of the tests is measured using both parametric and non-parametric methods, the correlation between them is determined, and the reproducibility of the loading test is examined. Because complete separation between the genotypes cannot be achieved by these tests, a method of interpretation which avoids possibly erroneous categoric statements and which enables the family history of a subject and his test result to be combined in a quantitative and meaningful way is described.

Chemical studies on postmortem tissues from an infant with a sphingomyelin storage disorder.

Investigations of formalin-stored tissues from a female child 3 weeks old showed that the concentrations of sphingomyelin, cholesterol and other lipids were increased in spleen and other tissues. Although the disorder could not be confirmed enzymatically, the findings are most consistent with the patient having a sphingomyelin storage disorder. Tissue lipid data for a series of subjects without storage disorders are presented and may provide useful information for interpretation of results from autopsy samples.

Neonatal screening for sickle haemoglobinopathies in Birmingham.

During 1978-81 there were about 43,500 births in Birmingham, of which 10.3% were to Negroes and 22.6% to Asians. Cellulose acetate electrophoresis of red cell haemolysates from capillary specimens collected for phenylketonuria screening was performed for these babies to assess the feasibility, cost, and benefits of detecting sickle haemoglobinopathies early. Eight babies had important haemoglobinopathies; four were homozygotes for haemoglobin S (HbS), three were mixed heterozygotes for HbS and haemoglobin C (HbC), and one had haemoglobin E (HbE) and beta-thalassemia. Also, 534 (1.19%) were heterozygotes for HbS or haemoglobin D (HbD) and 205 (0.46%) for HbC or HbE, 453 (1.01%) were heterozygotes with a fast-moving band, one was a heterozygote for haemoglobin Norfolk, and one a heterozygote for both HbS and haemoglobin G Philadelphia. The cost of neonatal screening for haemoglobinopathies was 12.5 p per baby (705 pounds for each serious abnormality).

Lead intoxication in children in Birmingham.

Of 38 children investigated between 1966 and 1971 who had a blood lead concentration greater than 37 mug/100 ml eight had encephalopathy and one died; all these eight had a blood lead concentration of 99 mug/100 ml or above. Blood lead levels are related to haemoglobin concentrations and anaemia is common in children with blood lead concentrations of 37-60 mug/100 ml, levels previously accepted as harmless.Children with blood lead concentrations greater than 60 mug/100 ml show radiological evidence of lead intoxication, and treatment for this should be considered when blood lead concentration exceeds 37 mug/100 ml. Children presenting with unexplained encephalopathy should be radiographed for evidence of lead intoxication.

Screening for abnormal haemoglobins: a pilot study.

A pilot study has been made of the implication of screening for abnormal haemoglobins in immigrant schoolchildren. An abnormality was detected by capillary blood haemoglobin electrophoresis in 8.4% of 6,835 children and a haemoglobinopathy outpatient clinic had to be established to deal with the heavy work load which resulted. The clinic was also used to determine the value of investigating the remaining members of the family once an abnormality had been detected in one child.Healthy siblings with normal haemoglobin electrophoretic patterns and normal iron and folate levels were studied to determine a normal range for haemoglobin in relation to age for adequately nourished immigrant children. The lower limit of the normal range was close to the mean value minus 1(1/2) S.D.; by using this definition 10.3% of 280 children were subsequently found to be anaemic.Population screening of this type is desirable, but further pilot studies of patient education, genetic counselling, organization of specimen collection, data processing, and follow-up health care facilities are required before screening is extended more widely in the United Kingdom.

Screening for inherited metabolic disease by plasma chromatography (Scriver) in a large city.

Before introducing a more comprehensive screen such as plasma chromatography, with its potential to detect 20 amino-acid disorders-an advantage over screening methods which detect only phenylketonuria-the greatly increased problems of organization and the effect on the community, midwives, paediatric services, and laboratory should be considered. The three years' experience in Birmingham showed a three-fold increase in cases detected and suggests criteria for further investigation and treatment.

Biopterin derivatives in normal and phenylketonuric patients after oral loads of L-phenylalanine, L-tyrosine, and L-tryptophan.

Plasma biopterin derivatives studied in 10 normal and 21 phenylketonuric children showed a significantly high concentration in the latter group. Biopterin derivatives correlated with plasma phenylalanine concentration, but in normal adults given an oral phenylalanine load the rate of increase with phenylalanine differed from that in phenylketonuric patients. A patient with hyperphenylalaninaemia, not due to phenylketonuria, had an abnormal biopterin derivatives response to phenylalanine distinct from that of patients with classical phenylketonuria. This may be a useful investigation to differentiate some variants of phenylketonuria.

Faecal composition after surgery for Hirschsprung's disease.

Diarrhoea and perianal excoriation occur frequently after the endorectal pull-through operation for Hirschsprung's disease. A new method of faecal analysis was performed on 3-day stool collections in 17 postoperative Hirschsprung patients and in 14 normal children, in order to define the faecal abnormality and to establish the cause of perianal excoriation in these patients. Loose stools in postoperative patients were deficient in dry solid content and contained an excess of extractable faecal water. This also had a raised electrolyte concentration, particularly with respect to sodium. Total daily output of faecal water was normal. Formed stools from postoperative patients were also deficient in drysolids but had a normal extractable water content. Excess extractable faecal water, the main abnormality of loose stools in these patients, is the result of abnormal water absorption from the distal colon. Perianal excoriation in these patients is most closely associated with the concentration of sodium in faecal water.