Urinary pyridinoline and deoxypyridinoline excretion in children

OBJECTIVE

There are few data on urinary markers of collagen breakdown in children. We have determined a normal range for urinary pyridinoline and deoxypyridinoline in children, assessed the variability in excretion in individual children and examined the effect of GH treatment on the excretion of these collagen cross-links.

DESIGN

A cross-sectional study of a group of healthy children and sequential samples from children receiving GH treatment.

PATIENTS

One hundred and nine healthy children aged 2-15 years, 8 healthy children aged 4-11 years and 4 children receiving GH treatment.

MEASUREMENTS

Total pyridinoline and deoxypyridinoline excretion were measured by high performance liquid chromatography after initial acid hydrolysis and cellulose extraction steps. Serum parathyroid hormone was measured using a two-site immunoradiometric assay and urinary hydroxyproline by Ehrlich's reaction using a colorimetric assay. Pyridinoline and deoxypyridinoline excretion were expressed as a ratio against urine creatinine.

RESULTS

High excretion of pyridinoline (Pyr) and deoxypyridinoline (DPyr) was seen at all ages with no apparent relation to age (mean Pyr/Cr 115 nmol/mmol and DPyr/Cr 31 nmol/mmol). No correlation was found with serum parathyroid hormone or urinary hydroxyproline excretion. Marked day to day variation was seen in individual children. A progressive rise in excretion was seen in children receiving GH treatment with no significant correlation to height velocity.

CONCLUSIONS

There is a high excretion of the pyridinium cross-linking amino acids in children of all ages compared to adults. However, a high variability exists in single morning urine samples which will limit the usefulness of these markers in growing children.

Accident and emergency monitor

This paper describes the development of a set of practical quality audit criteria relevant to the examination of nursing care delivered to patients and relatives in hospital Accident and Emergency (A & E) departments. The project was initiated by senior nurse managers at the North Staffordshire Royal Infirmary, UK, conducted in partnership with Leeds Polytechnic (now the Leeds Metropolitan University), UK, and received further sponsorship from the Royal College of Nursing Accident and Emergency Association.

Effects of aging on AV nodal and ventricular beta-adrenergic receptors in the Fischer 344 rat

The effects of aging on atrioventricular (AV) nodal and right and left ventricular beta-adrenergic receptor (beta-AR) characteristics were studied in Fischer 344 rat hearts using quantitative autoradiography. Twenty-micrometer-thick cardiac sections containing the compact AV node from 16 mature (4-6 mo old) rats, 6 middle-aged (12 mo old) rats, and 16 old (24 mo old) rats were incubated with [125I]iodocyanopindolol, [125I]iodocyanopindolol plus atenolol, or ICI 118551. Saturation experiments revealed a significant age-related decrease in AV nodal beta-AR density (mature: 190 +/- 46, middle-aged: 165 +/- 27, old: 133 +/- 34 amol/mm2; P < 0.01), with no change in affinity (mature: 106 +/- 62, middle-aged: 132 +/- 46, old: 128 +/- 66 pM). No age-related changes in AV nodal beta-AR subtype ratio (55% beta 1, 45% beta 2) or estimated compact AV node volume were detected (mature: 66 +/- 17, old: 65 +/- 23 microns 3). No difference in beta-AR density or affinity was detected between mature and old rats in either left (LV) or right (RV) ventricular tissue (LV, mature: 60 +/- 11, middle-aged: 59 +/- 11, old: 62 +/- 11 amol/mm2; RV, mature: 65 +/- 9, middle-aged: 65 +/- 11, old: 58 +/- 10 amol/mm2). beta-AR subtype ratios for the left ventricle (64% beta 1, 36% beta 2) and right ventricle (63% beta 1, 37% beta 2) did not significantly differ between mature and old rats. To summarize, aging from 4 to 24 mo in the Fischer 344 rat is associated with 1) a decrease in AV nodal beta-AR density with no change in affinity; 2) no change in volume of the compact region of the AV node; 3) no change in beta-AR subtype ratio in the AV node, left ventricle, or right ventricle; and 4) no change in either RV or LV beta-AR density.

Oxygen and 99mTc-MAA shunt estimations in patients with pulmonary arteriovenous malformations: effects of changes in posture and lung volume

BACKGROUND

Patients with arteriovenous malformations are routinely monitored with arterial oxygen saturation (SaO2) estimations (breathing air) from which an oxygen shunt fraction can be calculated. This simple estimation has been compared with an anatomically defined estimate of the right to left shunt using a radioisotopic method. The fall in SaO2 which occurs in patients with pulmonary arteriovenous malformations in the erect posture and at high lung volumes was used to test the ability of SaO2 alone to follow changes in right to left shunt.

METHODS

Radiolabelled albumin macroaggregates (99mTc-MAA) or microspheres (MS) were injected intravenously and kidneys and lungs were imaged. The shunt fraction (QS/QTTc) in the supine position at functional residual capacity (baseline) was obtained by quantifying right kidney radioactivity. On standing or while breath holding at total lung capacity, shunt fraction was calculated from baseline QS/QTTc and from lung counts and the injected dose. Arterial oxygen saturation (SaO2) was recorded by a pulse oximeter for calculation of the oxygen shunt (QS/QTO2) (breathing air).

RESULTS

In the postural study (n = 8) SaO2 decreased from a mean (SD) value of 89 (5)% supine to 80 (6)% erect, corresponding to QS/QTO2 28 (8)% and 44 (8)% respectively. QS/QTTc increased from 28.7 (10.3)% to 39 (14.3)%. In the lung volume study (n = 8) QS/QTTc increased from 16.6 (11.5)% at functional residual capacity to 23.3 (11.9)% at total lung capacity while QS/QTO2 increased from 19.5 (7.5)% to 25.9 (10.6)% respectively. When all measurements were compared for QS/QTTc% and QS/QTO2% (n = 32) the difference in the mean values was 2.5% (absolute) and the limits of agreement between the two methods were +38% to -18% (relative). In neither the postural nor the volume study did delta (QS/QTO2) reliably predict delta (QS/QTTc)%.

CONCLUSIONS

In pulmonary arteriovenous malformations the simple physiological shunt calculated from SaO2 breathing air agreed well with the anatomical right to left shunt measured with 99mTc-MAA, but predicted poorly the changes in anatomical shunt induced by postural or lung volume changes.

Routine outpatient L-dopa monitoring in elderly patients with Parkinson's disease

In an attempt to improve the therapeutic drug management of patients with Parkinson's disease, plasma L-dopa concentrations were measured by high-performance liquid chromatography and related to the post-dose time with reference to an established therapeutic range of 0.3-1.6 mg/l. The response to treatment was also assessed. One hundred and three samples were obtained at morning clinics from 53 elderly patients (mean age 72.5 years) taking an L-dopa/decarboxylase inhibitor combination. L-Dopa concentrations ranged from 0.01 to 3.6 mg/l. Fifty-nine values were within, 39 values were below and five values were above the therapeutic range. Three values were at or below the lower limit of the assay and probably indicated poor compliance. L-Dopa concentration was significantly negatively correlated with post-dose time for the dosage groups of 50 mg (p = 0.04), 100 mg (p = 0.0013), 200-250 mg (p = 0.055) and for the combined data (p = 0.005). Post-dose times were from 35 to 400 min, with the majority greater than 90 min, and it is likely that most of these corresponded to the post-peak phase of L-dopa absorption. There was a tendency for a good response to treatment to occur with values within and above the therapeutic range and for dyskinesia to be more common above the therapeutic range. It was concluded that plasma L-dopa measurement at known post-dose time, 90-360 minutes after the morning dose, can identify non-compliance, patients at risk of dose related side-effects and give useful information about the suitability of the L-dopa dose.

Evaluation of edrophonium as a provocative agent for vasovagal syncope during head-up tilt-table testing

Vasovagal syncope after head-up tilting is thought to be secondary to a complex, neurally-mediated reflex with both vasodepressor and cardioinhibitory efferent components. The efficacy of edrophonium, an acetylcholinesterase inhibitor, as a provocative agent for triggering syncope during head-up tilt testing was evaluated. Forty-five consecutive patients (22 female and 23 male) with history of recurrent unexplained syncope received edrophonium (10 mg intravenous) after 30 minutes of 60 degrees head-up tilting alone. Twenty normal control subjects (9 female and 11 male) were tested with head-up tilt testing and edrophonium. Syncope was induced in 19 of 45 patients with the diagnosis of unexplained syncope. In 9 patients who developed syncope with head-up tilting alone, the predominant hemodynamic finding was marked vasodepression. In contrast, in 10 patients who developed syncope only after head-up tilting and edrophonium, the predominant hemodynamic findings were marked vasodepression and bradycardia. Syncope was induced in 1 of 20 normal subjects after head-up tilting and edrophonium. There was no long-term complication from using edrophonium. It is concluded that head-up tilt testing with edrophonium: (1) significantly increases the identification of patients with vasovagal syncope, (2) may be particularly useful when provocation with isoproterenol is undesirable, and (3) may be an effective method to help differentiate patients with a significant reflex cardioinhibitory component from those with a predominantly reflex vasodepressor component.

A five-compartment model of body composition of healthy subjects assessed using in vivo neutron activation analysis

A body composition study of 31 healthy subjects covering a wide range of age (23.5-72.0 years) and weight (44.5-104.2 kg) has been undertaken. Subjects were assessed by in vivo neutron activation and tritiated water analysis and values of total body nitrogen, hydrogen and fat obtained by utilization of a five-compartment model of body composition comprising protein, water, fat, minerals and glycogen. The protein (as 6.25 x nitrogen) and water compartments were measured but the smaller compartments of minerals and glycogen were calculated as fixed fractions of the fat-free mass estimated from the water space. Fat was calculated as the body mass less the sum of the four other compartments. Mean values (+/- SEM), expressed as a percentage of body mass, for nitrogen, hydrogen and fat were 2.56 (+/- 0.07)%, 10.07 (+/- 0.04)%, and 21.9 (+/- 1.7)% respectively for men and 2.14 (+/- 0.07)%, 10.40 (+/- 0.04)%, and 35.5 (+/- 1.7)% respectively for women. The accuracy of the nitrogen measurements was evaluated by comparison with calculated values from two prediction equations; correlation coefficients, the mean bias (estimated from the mean differences between the measured and predicted nitrogen), the confidence interval for the bias, and limits of agreement were calculated. The correlation coefficients were high (r > 0.93) and the mean bias indicative of agreement. The ratio of nitrogen to the fat-free mass (derived from the body composition model) was also calculated and mean values (+/- SEM) of 32.7 (+/- 0.4) and 33.1 (+/- 0.4) g/kg for men and women, respectively were obtained. The hydration of the fat-free mass was determined to be 0.725 (+/- 0.002) and 0.722 (+/- 0.002) kg/kg for men and women respectively. The accuracy of the body fat estimate was evaluated by comparison with skinfold-thickness-derived values and computation from tritiated water space. The ratio of the body composition model to skinfold-thickness-derived fat was significantly (P < 0.005) greater than unity. The mean bias between the body composition model and tritiated-water-derived fat was -0.6 percentage points of fat (95% confidence interval from -0.3 to -0.9 percentage points of fat). Finally a prediction equation (r2 = 0.908, SEE = 108 g) for body nitrogen in healthy subjects based on weight, age and sex was calculated.

The measurement of silicon in a lung phantom--a comparison of two nuclear reactions for in vivo activation analysis

The amount of silica in the human lung may be estimated by measurement of silicon using in vivo neutron activation analysis. A pulsed, fast neutron beam, produced with a 2 MV Van de Graaff generator using the 2H + 2H reaction, was used to irradiate a Si-doped chest phantom in order to determine minimum detection limits (MDL). Two 'in-beam' nuclear reactions on Si were studied; prompt fast neutron inelastic scatter 28Si (n,n' gamma)28Si reaction was measured during the beam burst and the slow neutron prompt capture reaction was measured between the fast neutron bursts. Although the latter reaction appeared less favourable due to neutron cross section and measurement efficiency considerations, it yielded an MDL of 1.8 g compared with 2.3 g for the 28Si(n,n' gamma)28Si reaction. A comparison was made with a 252Cf neutron irradiation system where a Si MDL of 6.3 g was obtained using the slow neutron capture reaction. The Van de Graaff system permits 'exposed' Si lung burdens to be measured but not normal levels. Improved measurement sensitivity may be achieved by reduction of high counting-rate losses and high background radiation.

Characterization of a Flavobacterium glutathione S-transferase gene involved reductive dechlorination

The gene pcpC, encoding tetrachloro-p-hydroquinone (TeCH) reductive dehalogenase, was cloned from Flavobacterium sp. strain ATCC 39723 and sequenced. The gene was identified by hybridization with a degenerate oligonucleotide designed from the N-terminal sequence of the purified protein. An open reading frame of 747 nucleotides was found, which predicts a translational product of 248 amino acids having a molecular weight of 28,263, which agrees favorably with the sodium dodecyl sulfate-polyacrylamide gel electrophoresis-determined molecular weight of 30,000 reported for the purified protein. The predicted translational product of pcpC matched the N-terminal sequence of the purified protein exactly. From the nucleotide sequence, the protein appears to have a processed formylmethionyl. An Escherichia coli pcpC overexpression clone was shown to produce dichlorohydroquinone and trichlorohydroquinone from TeCH. Protein data base searches grouped the predicted translational sequence of pcpC with two previously reported plant glutathione S-transferases but less significantly with any of the mammalian glutathione S-transferases or the glutathione-utilizing, hydrolytic dechlorinating enzyme from Methylobacterium sp. strain DM4.

Measuring L-dopa in plasma and urine to monitor therapy of elderly patients with Parkinson disease treated with L-dopa and a dopa decarboxylase inhibitor

We have established a method for measuring L-dopa in plasma and urine, including the metabolites dopamine and L-dopac, using separation by ion-pair reversed-phase HPLC and quantification with an electrochemical detector. The assay was applied to the therapeutic monitoring of elderly patients with established Parkinson disease being treated with L-dopa plus a dopa decarboxylase inhibitor. Plasma L-dopa was evaluated in relation to dosage and postdose sampling time in 71 outpatients with Parkinson disease. L-Dopa concentrations were greatest in the patients taking the highest dosages prescribed and decreased significantly with increasing time after postdose sampling. Comparison of plasma L-dopa concentrations with a published therapeutic range established by intravenous administration of L-dopa was helpful in assessing the suitability of each patient's drug dosage, assessing patients' compliance, and avoiding overdosage but was not useful in the overall clinical assessment of progression of disease or of the long-term therapeutic response. Urine measurements confirmed the plasma concentrations but showed no further advantage. The recommended time for sample collection is between 1.5 and 3 h after the first morning dose. Plasma is the preferred matrix but if blood sampling is difficult, particularly from elderly/infirm individuals, an untimed urine collection could be used.

Measuring L-dopa in plasma and urine to monitor therapy of elderly patients with Parkinson disease treated with L-dopa and a dopa decarboxylase inhibitor

We have established a method for measuring L-dopa in plasma and urine, including the metabolites dopamine and L-dopac, using separation by ion-pair reversed-phase HPLC and quantification with an electrochemical detector. The assay was applied to the therapeutic monitoring of elderly patients with established Parkinson disease being treated with L-dopa plus a dopa decarboxylase inhibitor. Plasma L-dopa was evaluated in relation to dosage and postdose sampling time in 71 outpatients with Parkinson disease. L-Dopa concentrations were greatest in the patients taking the highest dosages prescribed and decreased significantly with increasing time after postdose sampling. Comparison of plasma L-dopa concentrations with a published therapeutic range established by intravenous administration of L-dopa was helpful in assessing the suitability of each patient's drug dosage, assessing patients' compliance, and avoiding overdosage but was not useful in the overall clinical assessment of progression of disease or of the long-term therapeutic response. Urine measurements confirmed the plasma concentrations but showed no further advantage. The recommended time for sample collection is between 1.5 and 3 h after the first morning dose. Plasma is the preferred matrix but if blood sampling is difficult, particularly from elderly/infirm individuals, an untimed urine collection could be used.

An enzymatic fluorometric assay for adenylate cyclase activity

Adenylate cyclase, the catalytic protein that converts ATP to cAMP, plays a fundamental role in adrenergic signal transduction. Adenylate cyclase activity (pmol cAMP/mg/min) is generally assayed by measuring radiolabeled cAMP generated from [alpha-32P]ATP. Although sensitive, the radioactive approach is costly and time consuming. Given safety and environmental concerns, we developed a highly sensitive fluorometric assay for adenylate cyclase activity. This assay depends upon the breakdown of cAMP by phosphodiesterase to AMP, and the subsequent stimulation by AMP of glycogen phosphorylase a. Radioactive and fluorescence methods were compared using the same ventricular membrane preparations from five different rabbit hearts. Theophylline, used in the fluorometric assay, increased basal adenylate cyclase activity. However, adenylate cyclase kinetics, the dose response to isoproterenol, and the "fold" stimulation (agonist stimulated/basal adenylate cyclase activity) after isoproterenol (10(-6)M), guanylyl-5'-imidodiphosphate (GppNHp) (10(-4)M), and NaF (10(-2)M) were nearly identical with both methods. Adenylate cyclase activity can be measured with the fluorometric assay in samples as small as 10 micrograms of membrane protein. In summary, this new fluorometric assay is highly sensitive, safer, less costly, and less time consuming than radioactive assays for adenylate cyclase activity.

Pyrophosphate in synovial fluid and urine and its relationship to urinary risk factors for stone disease

Inorganic pyrophosphate (PPi) measurement in urine and synovial fluid has been established using the PPi-dependent phosphorylation of fructose-6-phosphate and subsequent reduction of dihydroxyacetone phosphate by NADH. The assay is linear up to 200 mumol/L, easy to perform and gives results comparable to more complex methods. Daily urinary output of PPi was independently related to both age (P = 0.0014) and sex (P = 0.0002). Men had higher values than women and older individuals excreted greater amounts. Male stone formers, younger than 45 years, had lower values than age matched male controls (P = 0.012). Younger female stone formers also tended to have lower values. In stone formers' urine significant and independent correlations were found of PPi excretion with urine volume (P = 0.004) and with phosphate excretion (P = 0.008). Oxalate excretion and that of other urine constituents and the degree of supersaturation with common stone-forming salts were not correlated with PPi. PPi excretion was markedly elevated in the urine of two patients with hypophosphatasia. The PPi concentration in synovial fluid from painful, swollen knee joints was elevated, but unrelated to the presence or absence of PPi or urate crystals.

Regional distribution of ECS in contractile and conductive elements of rat and rabbit heart

By adaptation of recently developed quantitative microanalytic techniques, the size of the extracellular space (ECS) was measured regionally in the rat and rabbit cardiac conductive and contractile tissues. When inulin and sucrose were measured as extracellular markers in rabbit heart, the ECS in the atrioventricular (AV) node was found to be, respectively, 2.4 and 2.2 times larger than that of adjacent ventricular muscle. By use of inulin, the ECS in the rabbit His bundle was found to be 1.8 times larger than the adjacent ventricular tissue. Similarly, when inulin was used in rat, the ECS of the AV node, His bundle, right bundle branch, and right atrium was found to be, respectively, 2.5, 1.9, 1.8, and 1.2 times larger than that of left and right ventricular muscle. Similarly, significant regional differences in ECS were also observed in rat heart with sucrose. By use of glucose as an ECS marker, these results also revealed a 2.5-2.9 times larger ECS in rat and rabbit AV node compared with contractile elements. In contrast, ATP content, measured as an intracellular marker, was the same in both AV nodal and ventricular muscle tissue from both rat and rabbit. These data demonstrate that there are significant regional variations in ECS within the cardiac conduction system. Collectively, the data obtained with all extracellular markers indicate that the size of the ECS of the conduction system is markedly larger than the adjacent contractile muscle.