Contrasted pollen capture mechanisms in Phyllocladaceae and certain Podocarpaceae (Coniferales).

Comparative study shows that Phyllocladus and representative Podocarpaceae differ in the mechanism by which pollen is introduced into the pollen chamber and onto the apex of the nucellus ("pollen capture"). Both types involve a pollination drop, but only in Podocarpaceae is it consistently inverted and in contact with adjacent surfaces. Phyllocladus has functionally nonsaccate pollen (although a vestigial saccus has been claimed); its pollen is wettable and sinks in water. Podocarpaceae (except Saxegorhaea) have saccate pollen, which is nonwettable and floats on water. In Phyllocladus the pollination drop receives the pollen directly and presence of pollen stimulates complete drop withdrawal, which may be a metabolic process. Once pollinated, an ovule does not resecrete a pollination drop. In Podocarpaceae the drop usually receives the pollen indirectly via pollen scavenging and saccate pollen is preferentially captured. The retraction of the drop appears to be the result of evaporation and is presumably nonmetabolic. Drop secretion can be repeated in the presence of pollen. A major consequence of these contrasted mechanisms is that in Phyllocladus the entire contents of the pollination drop are ingested, whereas in Podocarpaceae only that part of the drop that includes saccate pollen is ingested. Because of differences in repeatability of the secretion process, Podocarpaceae are likely to capture more pollen. In neither mechanism does the process favor 'own" pollen. but in Podocarpaceae all but saccate pollen is excluded. We thus have further evidence for differences in pollen capture mechanisms in conifers with a pollination drop, and differences in the behavior of the pollination drop itself.

Serum glutathione S-transferase B1 activity as an index of liver function in cystic fibrosis.

AIMS: To evaluate serum glutathione S-transferase B1 (GST B1), a highly sensitive test of hepatocellular function, as a means of identifying liver disease in patients with cystic fibrosis (CF). METHODS: The presence of liver disease was sought over a three year period in 60 children with CF, using a combination of clinical assessment, ultrasound examination, conventional biochemical tests of liver function (LFTs), and measurement of GST B1. RESULTS: Reference ranges for serum GST B1 were established in a paediatric control population. The 95% value (4.55 micrograms/l) was similar to the upper limit of normal previously derived in adults. Mean (SE) serum GST B1 activities were higher in the CF population (9.0 (1.14) micrograms/l) than in age matched controls (2.4 (0.15) micrograms/l). Ten patients with CF showed clinical signs of liver dysfunction. All but one had a serum GST B1 > 4.55 micrograms/l. Twelve other patients had elevated LFTs without clinically evident liver dysfunction, six had abnormal ultrasound scans and two showed both of these anomalies. Thirty patients with CF had neither biochemical, ultrasonographic nor clinical signs of liver disease. On review three years later, clinically important liver disease was reaffirmed in eight of the 10 index cases and had become apparent in a further eight, all of whom had elevated GST B1 activities. Five (36%) of the patients with elevated LFTs and two (33%) with isolated ultrasound changes continued to show these abnormalities. CONCLUSIONS: The limitations of conventional LFTs and ultrasound scans were evident from this study. The results suggest that elevated GST B1 activities may be a better predictor of hepatic dysfunction in CF than conventional LFTs.

Familial hypercholesterolaemia: pilot study to identify children at risk.

AIMS: To evaluate a more effective method of identifying children with familial hypercholesterolaemia by screening a population at high risk. METHODS: Domiciliary measurement of random cholesterol concentration was made in 200 children who were first or second degree relatives of subjects with premature onset coronary artery disease. Measurements were taken by a health visitor using a portable analyser. RESULTS: Twelve new cases of familial hypercholesterolaemia were identified during the first nine months of the study. Random cholesterol concentrations were within the normal range (< 5.2 mmol/l) in 70.5% of samples tested. Forty two (21%) of patients tested had a borderline cholesterol (5.2-5.9 mmol/l) but 50% of these fell within the normal range when fasting capillary samples were analysed. Children with significant hypercholesterolaemia on random testing (concentrations of > 5.9 mmol/l) (8.5%) also had fasting venous blood assayed for high density lipoprotein (HDL) cholesterol and tri-glyceride in the laboratory. Results indicated that 6.5% of patients screened were at high risk of cardiovascular disease (ratio of total: HDL cholesterol of > 4.5), and 1% had a moderately increased risk (ratio 3.5-4.5). CONCLUSIONS: Children with familial hypercholesterolaemia can be identified from a selected "high risk" population by measuring random capillary cholesterol concentration.

Homozygous acute intermittent porphyria: compound heterozygosity for adjacent base transitions in the same codon of the porphobilinogen deaminase gene.

A sister and brother with severe porphobilinogen (PBG) deaminase deficiency are described. Each of their parents carries a different mutation for acute intermittent porphyria and the children are homozygous for the PBG-deaminase deficiency that causes this disorder. Both are compound heterozygotes for adjacent base transitions in the same codon in exon 10 of the PBG deaminase gene.

The ratio of plasma phenylalanine to other large neutral amino acids is not a risk factor for tardive dyskinesia.

The ratio of the plasma concentration of phenylalanine (PA) to the sum of the plasma concentrations of other large neutral amino acids (LNAA) was calculated in 26 chronic, in-patient schizophrenics who met diagnostic criteria for tardive dyskinesia and 22 patients who did not. No difference in the PA/LNAA ratio was found between the two groups. Small positive correlations were found between age and both PA/LNAA ratio and tardive dyskinesia. Neuroleptic dose correlated negatively with both age and plasma PA/LNAA ratio. No support was found for previous reports of increased plasma PA/LNAA ratio in schizophrenic patients with tardive dyskinesia.

D(+)-glyceric aciduria: etiology and clinical consequences.

A family comprising mother, father, and five children is described. Four of the children were found to excrete massive amounts of D(+)-glyceric acid in their urine. This was verified by gas chromatography-mass spectrometry and the configuration determined by capillary gas chromatography of O-acetylated menthyl esters. The excretion ranged from 10.8 to 19.9 mmol/24 h. The remaining child and the parents showed no evidence of this unusual metabolite. The virtual absence of clinical manifestations in this family was particularly interesting. Only two of the children showed any clinical abnormality and this was limited to mild microcephaly and speech delay; the other two children found to excrete large amounts of D(+)-glycerate were healthy and developmentally normal at 7 y and 9 y of age. There was a marked increase in the excretion rate of D(+)-glycerate in response to both oral fructose and serine loading. These results are consistent with a deficiency of D(+)-glycerate kinase and indicate the potentially benign nature of this disorder.

Establishment of an external quality-assessment scheme for amino acid analyses: results from assays of samples distributed during two years.

Ten different samples of lyophilized plasma and two of liquid urine were distributed during two years to 26 laboratories performing quantitative amino acid analyses in a scheme designed to provide external quality assessment. After each distribution, statistical summaries and performance scores based on delta standard deviations and percentage biases from the all-laboratory trimmed means were returned to participants, who also received annual performance summaries based on their accumulated results. Coefficients of variation calculated from returns across all the samples ranged from 13% for glycine to 65% for methionine. Automated ion-exchange amino acid analyzers with ninhydrin detection appeared to perform better than other methods, although there was no clearly superior method and no model of analyzer clearly outperformed the others. These exercises demonstrate that there is room for improvement in the performance of quantitative amino acid analyses and that individual expertise may be more important in maintaining good performance than the choice of method or analyzer.

Isolated fructose malabsorption.

A patient with isolated fructose malabsorption presented with diarrhoea and colic during the first year of life and subsequently responded to a fructose free diet. Fructose malabsorption has been implicated in some cases of irritable bowel syndrome in adults and may also be an infrequently recognised cause of gastrointestinal symptoms in children.

Dried blood spot glucose measurement in hyperinsulinaemic hypoglycaemia.

A retrospective analysis of dried blood spot glucose profiles found them to provide useful information about the progress of a child with hyperinsulinism due to nesidiodysplasia. The potential for their use in the management of such cases is discussed.

Urinary excretion of 3-methylhistidine, creatinine and total nitrogen by Kenyan children during acute measles and after recovery.

The urinary excretion of 3-methylhistidine (3MH), creatinine and total nitrogen was measured during the course of energy balance studies on 20 black Kenyan children. Studies were carried out over 24 h during an acute attack of measles with a second (control) study after recovery, and complete urinary collections were obtained on 14 ill and 18 recovered children. The nutritional status was assessed by anthropometry, and energy intake was determined by duplicate diet analysis. Twelve out of 13 acutely ill and 6 out of 17 recovered children were in negative energy balance. No effect on the rate of excretion of 3MH or of creatinine attributable to differences in nutritional status, of energy intake or to infection was observed. The linear relationship between the excretion rate of all three metabolites and body weight which was observed in recovered children was absent during acute infection. Nitrogen excretion was correlated (P less than 0.05) with the level of energy intake. The linear relationship between the rate of excretion of 3MH and creatinine and of 3MH and nitrogen was significantly closer in recovered than in ill children. The simultaneous effects of infection, underfeeding (and oliguria) on the rate of excretion of protein metabolites may be complex and contradictory. Our results suggest that the excretion of 3MH, creatinine and nitrogen is sustained during infection accompanied by negative energy balance. Disruption during infection of the relationship between the excretion of all three metabolites and body weight, and between 3MH and the other two metabolites suggests perturbation in protein metabolism at this time.

Identification of the cause of separation (creaming) of lipid emulsions in intravenous infusion.

Over a 2-month period, white deposits were found in infusion sets delivering parenteral nutrition mixtures that included a lipid emulsion. When components of the infusion were mixed in the laboratory, separation (creaming) of the emulsion could be demonstrated, and this enabled us to predict the concentrations of the prescribed infusates that were likely to cream. Further investigations showed that creaming occurred when the lipid emulsion was mixed with heparin and calcium ions at concentrations above 1 U/ml and 1 mumol/ml, respectively.

Acceptance of domiciliary theophylline monitoring using dried blood spots.

Filter paper cards incorporating dried blood spots for the measurement of theophylline concentrations were returned by 62 out of 100 asthmatic children sent kits with instructions for their collection. Analysis of the blood spots showed that 37 (61%) of the children who returned them had less than therapeutic blood theophylline concentrations, in 21 (34%) they were therapeutic, and in three (5%) they were potentially toxic. The results indicate that most asthmatic children would comply with requests for home monitoring of theophylline concentrations, and that only one third of children receiving theophylline achieved blood concentrations and that only one third of children receiving theophylline achieved blood concentrations within the therapeutic range.

Transient neonatal galactosaemia.

A 4 week old infant who failed to thrive was found to have galactose in his urine. Plasma galactose concentration was grossly raised (4.48 mmol/l; reference range less than 0.24 mmol/l) but red cell transferase and epimerase activities were normal. He improved when dietary lactose was excluded. Clinical and biochemical tolerance to galactose was evident by 7 months of age.

Measurement of theophylline in dried blood spots by spectrophotometric enzyme immunoassay.

A widely-used enzyme immunoassay for the measurement of theophylline in plasma (EMIT) has been adapted for use with dried blood spots. Potential interference from haemoglobin in eluates of the spots was avoided by autoclaving them prior to analysis. The method was investigated in terms of the recovery of theophylline added to samples, precision, and the correlation of results in DBS with those in plasma samples. The recoveries of some other drugs from eluates of autoclaved DBS were also investigated.

Screening tests for glycosaminoglycans in urine: experience from regional interlaboratory surveys.

Three urine samples were distributed to laboratories in the Trent and Yorkshire regions to assess their ability to detect glycosaminoglycans. Satisfactory results were obtained for samples from patients with Hunter's and Morquio's diseases but six of 14 laboratories reporting a result for a Sanfilippo sample missed the abnormality. Replies to a subsequent questionnaire showed that unsuccessful laboratories were not using recommended screening methods, that they lacked experience in testing for these diseases, and that rationalisation of such screening services may be indicated.