A single ancient origin of brood parasitism in African finches: implications for host-parasite coevolution.

Robust phylogenies for brood-parasitic birds, their hosts, and nearest nesting relatives provide the framework to address historical questions about host-parasite coevolution and the origins of parasitic behavior. We tested phylogenetic hypotheses for the two genera of African brood-parasitic finches, Anomalospiza and Vidua, using mitochondrial DNA sequence data from 43 passeriform species. Our analyses strongly support a sister relationship between Vidua and Anomalospiza, leading to the conclusion that obligate brood parasitism evolved only once in African finches rather than twice, as has been the conventional view. In addition, the parasitic finches (Viduidae) are not recently derived from either weavers (Ploceidae) or grassfinches (Estrildidae), but represent a third distinct lineage. Among these three groups, the parasitic finches and estrildids, which includes the hosts of all 19 Vidua species, are sister taxa in all analyses of our full dataset. Many characters shared by Vidua and estrildids, including elaborate mouth markings in nestlings, unusual begging behavior, and immaculate white eggs, can therefore be attributed to common ancestry rather than convergent evolution. The host-specificity of mouth mimicry in Vidua species, however, is clearly the product of subsequent host-parasite coevolution. The lineage leading to Anomalospiza switched to parasitizing more distantly related Old World warblers (Sylviidae) and subsequently lost these characteristics. Substantial sequence divergence between Vidua and Anomalospiza indicates that the origin of parasitic behavior in this clade is ancient (approximately 20 million years ago), a striking contrast to the recent radiation of extant Vidua. We suggest that the parasitic finch lineage has experienced repeated cycles of host colonization, speciation, and extinction through their long history as brood parasites and that extant Vidua species represent only the latest iterations of this process. This dynamic process may account for a significantly faster rate of DNA sequence evolution in parasitic finches as compared to estrildids and other passerines. Our study reduces by one the tally of avian lineages in which obligate brood parasitism has evolved and suggests an origin of parasitism that involved relatively closely related species likely to accept and provide appropriate care to parasitic young. Given the ancient origin of parasitism in African finches, ancestral estrildids must have been parasitized well before the diversification of extant Vidua, suggesting a long history of coevolution between these lineages preceding more recent interactions between specific hosts and parasites.

Low plasma haptoglobin in march haemoglobinuria.

A student had haemoglobin in the urine after running but not after cycling. The haemoglobinuria was related to the hardness of the surface on which he ran and to his running style. The concentration of haptoglobin in his plasma was less than normal. This was most pronounced after he had been running, when haptoglobin had combined with free haemoglobin, but the concentration was also low when there had been no haemolysis for six weeks. Thus two factors combined to give him haemoglobinuria: lysis of red cells by mechanical damage and lack of haptoglobin to combine with liberated haemoglobin.

Adjusted calcium conflict resolved? Differing effects on plasma total calcium of changes in plasma albumin after venous stasis or myocardial infarction.

Others have challenged the concept of adjusting total plasma calcium for albumin concentration on the grounds that after the application of a tourniquet the increase in calcium for a given increase in albumin differs significantly between normal individuals. We have confirmed this finding. In contrast, we have found that after myocardial infarction the fall in calcium for a given fall in albumin does not differ significantly between patients. Thus the adjustment of calcium for albumin using a single equation remains valid in patients with changes in albumin due to disease. We recommend that for consistent results blood should be taken with the minimum of venous stasis even though the patient's calcium is to be adjusted for albumin.

A method for deriving normal ranges from laboratory specimens applied to uric acid in males.

Plasma specimens from male blood donors gave a normal range for uric acid concentration of 3.3 to 7.5 mg/100 ml. Specimens from male outpatients, which were received in the laboratory for the analysis of urea but not of uric acid and proved to have normal concentrations of urea, showed a positively skewed distribution of values for uric acid from which a ;normal range' of 3.2 to 7.6 mg/100 ml was derived. We suggest that specimens from outpatients selected in the way described here may prove to be a convenient source of data for determining the normal range of other substances.

Interpretation of serum total calcium: effects of adjustment for albumin concentration on frequency of abnormal values and on detection of change in the individual.

Serum total calcium was measured in 1693 patients during a four-month period. We examined the effects of adjustment for albumin concentration on the interpretation of single measurements of serum total calcium and on the variation of series of measurements in individual patients. Markedly abnormal total calcium concentrations--2.75 mmol/l (11.0 mg/100 ml) or more, or 2.00 mmol/l (8.0 mg/100 ml) or less--were found in 115 patients, but only 24 (21%) remained markedly abnormal after adjustment for albumin. Three patients, two with malignant disease and one with primary hyperparathyroidism, had significant hypercalcaemia which was masked by hypoalbuminaemia. The serum total calcium measured on a subsequent occasion had changed 0.15 mmol/l (0.6 mg/100 ml) or more in 60 patients, but after adjustment for albumin this number was reduced to 27 (45%). The within-person standard deviation for serum total calcium was calculated in 26 patients with normal mean adjusted calcium concentrations who had had six or more sequential measurements. The mean standard deviation was 0.148 mmol/1 (0.59 mg/100 ml) and, after adjustment for albumin, this was reduced to 0.100 mmol/1 (0.40 mg/100 ml). We conclude that adjustment of serum total calcium concentration for albumin is essential to detect abnormal values and to assess changes in a value.

Mnemonic coding system for clinical data entry into laboratory computers: its effect on quality and efficiency.

A simplified coding method for entering the clinical details found on pathology request cards was developed. The method uses a basic four letter code, derived from the initial character of the first four words in a clinical detail, being expanded to four characters with letters from the final word if the number of words is less than four. Rules were devised to cope with common medical terminology. In excess of 90% of clinical details on request cards are readily input by clerical staff using our coding system, and 8% of clinical details are used intelligently by the computer in scheduling further tests or automatically commenting on results. A carefully designed coding system such as the one outlined above could greatly facilitate input of clinical detail without the penalty of reduced throughput.

The Leeds regional quality control scheme for clinical biochemistry: a progress report.

The results from a regional quality control scheme for clinical biochemistry are analysed. Comparison with results from an earlier period shows that the quality of several of the 15 routine analyses has improved. The methods by which the sera are produced and distributed, and the weekly results are analysed, are described. Each of the 25 laboratories receives an individual weekly computer printout within 24 hours of the deadline for the receipt of results. At the end of each six-month period a printout is produced ranking each laboratory for ;accuracy' and ;precision' for each test.

Comparison of an all-aqueous automated urine pregnancy oestrogen method with one using organic solvent extraction.

A comparative study between an all-aqueous automated urine pregnancy oestrogen method and a well established one requiring organic solvent extraction showed good agreement (r = 0.992). Advantages offered by the all-aqueous method include a faster rate of sample analysis and elimination of the difficulties of phase separation. The storage of urine for 5 days did not affect the oestrogen concentration measured by the all-aqueous method. Glucose, which reduced the apparent oestrogen concentration, was readily removed by treatment of the urine with borohydride, and treated urines showed good recoveries. The recovery of oestrogen was inadequate when glucose was removed from urine by incubation with yeast, possibly due to the formation of acetaldehyde.

Interpretation of urinary oestrogen:creatinine ratio for monitoring fetoplacental function in late pregnancy.

In pregnancies with a normal outcome the oestrogen:creatinine ratio in early morning samples of urine showed a smaller day-to-day variation than the ratio in 24-h urine or the 24-h total oestrogen excretion, and a significant fall could be detected more easily. Patients admitted to hospital who eventually delivered a healthy baby provided a reference range which, after logarithmic transformation, increased linearly with period of gestation. A fall in log10 oestrogen:creatinine ratio exceeding 40% of this range is unusual in pregnancies with a healthy outcome, and suggest impaired fetoplacental function.

An isotonic potassium chloride liquid junction minimises the effects of ionic strength, protein and haematocrit on ionised calcium measurement.

When the reference electrode liquid junction of a Nova 2 analyser was changed to isotonic potassium chloride, increasing the ionic strength of aqueous solutions containing a constant total calcium concentration had a negligible effect on measured ionised calcium. In contrast, measurements using hypertonic potassium chloride, hypertonic sodium formate and isotonic sodium chloride liquid junctions showed significant sample ionic strength effects. Interferences by sample protein concentration and haematocrit were marked with hypertonic, but negligible with isotonic junctions. Ionised calcium values in samples containing 25 mmol/L acetate, bicarbonate, beta-hydroxybutyrate, lactate or pyruvate were all lower by 6-7% with an isotonic than a hypertonic potassium chloride junction. Thus, anions that replace bicarbonate during metabolic acidosis have a similar effect on residual liquid junction potential. The clinical usefulness of an isotonic potassium chloride liquid junction needs to be evaluated.

Effects of ionic strength on ionized calcium measured using reference electrode liquid junctions of varying design and composition.

Five commercial analysers were used to measure ionized calcium in aqueous and protein solutions which contained the same amount of calcium but had sodium chloride concentrations ranging from 100 to 150 mmol/L. In aqueous solutions measured activity fell significantly with increasing ionic strength while in protein solutions it increased. When isotonic sodium chloride was substituted for the hypertonic potassium chloride reference electrode liquid junction of an analyser with an open junction, there was a marked positive change in the effect of ionic strength in both aqueous and protein solutions. In contrast, when either isotonic sodium chloride or potassium chloride was substituted for the hypertonic potassium chloride of an instrument with a membrane-restricted junction, there was no effect on the change of measured values with ionic strength. Increasing the protein concentration by ultrafiltration did not change ionized calcium values when isotonic reference solutions were used with either open or membrane-restricted junctions. Because membrane-restricted isotonic junctions respond like hypertonic junctions to changes in sample ionic strength but do not exhibit protein interference, they may prove to have advantages over both open isotonic junctions and all configurations of hypertonic junction for measurements in patients.

Clinically significant effect of protein concentration on ion-selective electrode measurements of ionised calcium.

Others, using an Orion SS-20 ionised calcium analyser, noted that the ionised calcium concentration of a native serum sample was 8% greater than that of its ultrafiltrate. The experiments described here, using a Nova 2 ionised calcium analyser, confirmed a positive protein interference which was greater for human albumin than for IgG. Uncharged dextran showed no positive interference but dextran sulphate, which is highly charged and binds calcium, showed a large effect. Thus the interference is related to macromolecular charge. Dialysis experiments with normal and pathological human serum samples indicated that the ionised calcium of diffusible plasma water was overestimated by an average of 9.6% at an albumin concentration of 40 g/l and by 4.8% at 20 g/l. It is concluded that the measurement of ionised calcium with existing analysers can be clinically misleading in patients with abnormal plasma proteins. Hypocalcaemia is likely to be overdiagnosed and hypercalcaemia underdiagnosed in the presence of hypoalbuminaemia.

Re-examination of effect of paracetamol on serum uric acid measured by phosphotungstic acid reduction.

The drug paracetamol (N-acetyl-p-aminophenol; acetaminophen) caused a spurious increase in serum uric acid measured by phosphotungstic acid reduction methods. However, the increase was less than 0.12 mmol/1 at plasma levels of paracetamol found in overdosage (40 mg/100 ml) and was small at therapeutic concentrations (less than 4 mg/100 ml). It is concluded that few patients with joint pain who have taken paracetamol paracetamol as an analgesic will have clinically misleading values for serum uric acid.

Serum albumin by dye-binding: bromocresol green or bromocresol purple? The case for conservatism.

Pooled patient's serum selected to have a wide range of albumin concentrations was analysed for albumin by bromocresol green with both long and short incubation times and also by bromocresol purple. Total protein, colloid osmotic pressure, calcium and magnesium were also measured. There were strong linear correlations between albumin measured by the three methods. Albumin values by bromocresol green with a short incubation time (1.5 min) averaged 5 g/L higher than those by bromocresol purple at all albumin concentrations. Colloid osmotic pressure correlated less strongly with total protein and with albumin by bromocresol purple than with albumin by the two bromocresol green methods. There were no significant differences between the correlation coefficients of calcium or magnesium with total protein and with albumin measured by the three methods. Bromocresol purple has no advantage over bromocresol green with a short incubation time for the clinical purposes for which albumin is measured: to detect abnormality, monitor change, predict colloid osmotic pressure and adjust calcium and magnesium for abnormal protein concentrations.

Protein interferes with ionised calcium measurement at the reference electrode liquid junction.

The ionised calcium concentration of sequential retentates prepared by ultrafiltration of a human control serum increased with increasing protein concentration when measured with both a Nova 2 and a Radiometer ICA1 analyser using their standard reference electrodes. In contrast, the ionised calcium in the same retentates fell slightly with increasing protein when the reference electrode liquid junctions of the instruments were changed from hypertonic to isotonic solutions, the values then paralleling those in the filtrates. Thus, the clinically significant positive relationship between ionised calcium and protein that has been reported with the Nova 2 and ICA1 analysers is almost certainly an effect of protein on the reference electrode liquid junction potential rather than a consequence of a Donnan effect on true ionised calcium distribution.

Adjustment of serum total calcium for albumin concentration: values change with age in women but not in men.

A total of 669 women and 609 men were selected from a laboratory computer data base in such a way that they would be expected to have a low prevalence of disturbances of calcium homeostasis but a wide range of serum albumin concentrations. The least squares regression coefficients of total calcium on albumin did not differ between men and women, nor did they differ at different ages. Mean serum albumin-adjusted calcium concentrations did not change with age in men from 1 to 90 years, and values were similar in women aged 1-20 years. However, adjusted calcium concentrations were significantly lower in women aged 21-50 and higher in women aged 61-90 than in younger women and all men. The differences were small and are unlikely to affect clinical interpretation.

An evaluation of the first production model of the Rank Hilger Chemispek multichannel electrolyte analyser.

The first production model of the Rank Hilger Chemispek multichannel analyser was evaluated. It is a six-channel machine for the analysis of sodium, potassium, chloride, bicarbonate, urea, and creatinine. We chose to run it at 120 samples per hour. The machine was shown to be economical in the volumes of both samples (200 microliters) and regents, flexible, accurate, and precise. It performance was better than that of other machines with a similar capacity and it is considerably cheaper.

Effects of workload and analysis time on the cost of out-of-hours investigations.

In the UK, under present Whitley Council Regulations for payment for out-of-hours pathology services, there is a complex relationship between the number of requests received, the time taken to analyse each request, and the number of calls for which payment may be claimed for work done. At a fixed average analysis time, the rate of increase of remuneration slows down as workload increases until at higher workloads remuneration falls. The introduction of methods with a shorter average analysis time to improve the clinical service increases remuneration disproportionately. We suggest that a fixed sessional payment would be a better way of funding the service.

Protein interference with ion-selective electrode measurement depends on reference electrode composition and design.

There is controversy about whether protein interferes with ion measurements using ion-selective electrodes. We have investigated the effects of changes in the salt-bridge composition of five commercially available analysers with open, membrane-restricted or porous frit-restricted reference electrode junctions on measurements of an albumin solution prepared by gel filtration. When the manufacturers' salt bridges were used, instruments with open or membrane-restricted junctions showed apparent increases in the activity of ionized calcium, sodium and potassium in the presence of protein. When the hypertonic bridge solutions were replaced with 150 mmol/L potassium chloride this increase disappeared. The instrument with a porous frit-restricted junction showed no protein effect, but its response to changes in sample sodium chloride concentration in protein-free solution suggested that its junction was functionally equivalent to that formed with an isotonic sodium chloride bridge. Our results emphasize that liquid junction design and composition affect ion measurements in protein-containing solutions and suggest that the use of hypertonic bridge solutions for biological samples needs to be re-examined.

Adjustment of serum total calcium for albumin concentration: effects of non-linearity and of regression differences between laboratories.

It has been reported that the relationship between serum total calcium and albumin concentrations in hospital patients deviates from linearity at low albumin concentrations. We searched a large laboratory computer data base for adult patients with discretionary requests for serum calcium analysis but with no other data suggestive of disturbances of calcium homeostasis, and collected a minimum of 100 calcium values at each of a wide range of albumin concentrations. We confirmed the earlier observation, but found that the use of a single regression to derive an adjustment of total calcium for albumin gave only small differences of no clinical significance. To investigate whether equations to adjust total calcium for albumin can be transferred between laboratories, three laboratory computers were searched for calcium requests from patients likely to have a low prevalence of calcium disturbances. The regressions of total calcium on albumin differed significantly between laboratories, but within each laboratory gave adjusted calcium values identical with those in health. Although the errors resulting from applying an equation from one laboratory to another were small and unlikely to be of major clinical significance, we recommend that where possible laboratories should derive adjustment equations from their own data.