Activity In Healthy Subjects Research Articles

The effect of physical effort on retinal activity in the human eye: rod and cone flicker electroretinogram studies

The aim of our study was to assess the effect of physical exercise with increasing intensity on neuroretinal activity in healthy subjects (n = 30). We analysed the amplitude and implicit time of b-wave electroretinogram (ERG) responses in two experiments: (1) for a scotopic blue 10 Hz flicker stimulus (rod-mediated responses), and (2) for a photopic white 30 Hz flicker stimulus (cone-mediated responses). Using a cycloergometer, three 10-minute effort-tests with increasing intensity were performed. Each participant was assigned individual workload values (W) below the lactate threshold (40% VO(2)max), at the lactate threshold (60-65% VO(2)max) and above the lactate threshold (80% VO(2)max). Five ERG recordings were taken: (1) before, (2-4) immediately after the three subsequent efforts and (5) 1 hour after the completion of the last effort. The right eye was selected for monocular stimulation in both experiments. After the first effort (40% VO(2)max), we observed an increased amplitude (p < 0.001) and decreased implicit time of the b-wave (p < 0.01) in cone-mediated responses, and no significant effects in rod-mediated responses. Despite the increase in effort intensity, the cone b-wave amplitude remained unchanged, whereas the rod b-wave amplitude significantly decreased after the subsequent efforts (p < 0.001). Rod-mediated responses were more susceptible to effort-induced homeostasis disruptions than the cone-mediated responses. The application of ERGs may be used as neurophysiological criteria in defining the cardiovascular status of the physical performance.

Regulation of Diurnal Variation of Cholesterol 7α-hydroxylase (CYP7A1) Activity in Healthy Subjects

Cholesterol 7alpha-hydroxylase (CYP7A1), the key regulatory enzyme of bile acid synthesis, displays a pronounced diurnal variation. To better understand the regulation of CYP7A1 activity, three day-long examinations were carried out in 12 healthy men. The concentrations of 7alpha-hydroxycholest-4-en-3-one (C4), a surrogate marker of CYP7A1 activity, bile acids (BA), insulin, glucose, nonesterified fatty acids, triglycerides, and cholesterol were measured in serum in 90-min intervals from 7 AM till 10 PM. To lower and to increase BA concentration during the study, the subjects received cholestyramine and chenodeoxycholic acid (CDCA), respectively, in two examinations. No drug was used in the control examination. There was a pronounced diurnal variation of C4 concentration with a peak around 1 PM in most of the subjects. The area under the curve (AUC) of C4 concentration was five times higher and three times lower when subjects were treated with cholestyramine and CDCA, respectively. No relationship was found between AUC of C4 and AUC of BA concentration, but AUC of C4 correlated positively with that of insulin. Moreover, short-term treatment with cholestyramine resulted in about 10 % suppression of glycemia throughout the day. Our results suggest that insulin is involved in the regulation of diurnal variation of CYP7A1 activity in humans.

Ice Application Effects on Peroneus Longus and Tibialis Anterior Motoneuron Excitability in Subjects with Functional Ankle Instability

ABSTRACTEvidence that focally cooling the ankle joint facilitates soleus and peroneus longus spinal reflex activity in healthy subjects has been reported. This response has been confirmed in individuals with a history of joint pathology for the soleus but not in the peroneus longus and tibialis anterior. The purpose of this study was to identify the effects of ankle cooling on isokinetic eversion and inversion torque and in peroneus longus, tibialis anterior H-reflex (Hmax:Mmax) in subjects with functional ankle instability (FAI). Twenty-four college aged subjects volunteered for this study. Peroneus longus and tibialis anterior Hmax:Mmax, and concentric eversion and inversion torque were recorded prior to and following each session. This protocol was used to compare FAI to healthy ankle group. There were no significant differences between groups. There were weak and no significant relationships between the corresponding muscles motoneuron excitability and their peak torque measurements. Ice application to the joint did not alter the peroneus longus or the tibialis anterior.

The Effect of Tooth Clenching and Grinding on Anterior Temporalis Electromyographic Activity in Healthy Subjects

The aim of this study was to determine the effect of tooth clenching and grinding on anterior temporalis electromyographic (EMG) activity. The sample included 30 healthy subjects with natural dentition and bilateral molar support, 15 with bilateral canine guidance and 15 with bilateral group function. An inclusion criterion was that subjects have to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the left and right anterior temporalis muscles. EMG activity was recorded during the following conditions: A. eccentric grinding from intercuspal position to the right lateral edge-to-edge contact position; B. clenching in right edge-to-edge lateral contact position; and C. concentric grinding from right lateral edge-to-edge contact position to intercuspal position. On the working side, EMG activity was not significantly different between conditions in both occlusal schemes. On the nonworking side, EMG activity was significantly higher during condition C than condition B in both occlusal schemes (mixed model with unstructured covariance matrix). When comparing by side, EMG activity was significantly higher during conditions A and B on the working side than on the nonworking side. However, there was no significant difference during condition C. EMG activity was significantly lower with canine guidance than group function on the working side (in all conditions) as well as during concentric grinding on the nonworking side. These results could explain muscular symptoms in the anterior temporalis muscles if the subject is experiencing parafunctional habits either while awake and/or sleep that exceed the individual’s adaptation capability.

Effect of Electroacupuncture on St. 36 (Zusanli) and LI. 10 (Shousanli) Acupuncture Points on Heart Rate Variability

Electrical stimulation of St. 36 (Zusanli) has been shown to enhance the regularity of gastric myoelectrical activity in healthy subjects. However, the underlying mechanism by which acupuncture alters gastric myoelectrical activity is still not clear. To elucidate the possible role of the autonomic nervous system in mediating the effect of acupuncture, we monitored heart rate variability (HRV), a widely used index of vagal discharge at the sinoatrial node of the heart before, during and after electroacupuncture. In this study, we applied two different frequencies (2 Hz and 100 Hz) of electrical stimulation at St. 36 (Zusanli) and LI. 10 (Shousanli) in 15 healthy volunteers. Low frequency (LF, sympathetic activity), high frequency (HF, vagal activity) and LF/HF ratio (sympathovagal balance) were analyzed and compared at the two different frequencies. The results showed an increase in the LF/HF ratio (indicating greater sympathetic activity) during the post-acupuncture period using 2 Hz of electrical stimulation at St. 36 (Zusanli). However, the overall change was not statistically significant. In addition, the power of LF and HF did not change significantly with electroacupuncture at St. 36 (Zusanli) and LI. 10 (Shousanli). In conclusion, applying 2 Hz or 100 Hz electroacupuncture at St. 36 (Zusanli) or LI. 10 (Shousanli) did not affect cardiovagal activity in normal volunteers. This phenomenon might be due to a difference in presentation in the autonomic nervous system between cardiac and abdominal vagal activity.

Tolerance of arabinoxylan-oligosaccharides and their prebiotic activity in healthy subjects: a randomised, placebo-controlled cross-over study

The tolerance and prebiotic effect following oral intake by healthy human subjects of arabinoxylan-oligosaccharides (AXOS), produced by partial enzymic hydrolysis of the wheat fibre arabinoxlyan, were studied. A total of twenty healthy subjects participated in the present randomised, placebo-controlled cross-over study. They consumed 10 g AXOS or placebo per d each for 3 weeks with a 4-week wash-out period in between. Before and immediately after each intake period, blood samples were taken to measure haematological and clinical chemistry parameters and the subjects completed a questionnaire about gastrointestinal symptoms. Additionally, urine was collected over 48 h for analysis of p-cresol and phenol content by GC-MS, and faeces were collected over 72 h for analysis of microbiota using real-time PCR. Of the subjects, ten also performed a urine and faeces collection 2 weeks after the start of intake (during intervention). A limited number of tested blood parameters were influenced in a statistically significantly way by either AXOS or placebo intake, but these changes remained within the normal range. Blood lipids remained unchanged. AXOS had no statistically significant effect on the range of gastrointestinal symptoms, except for a mild increase in flatulence. Urinary p-cresol excretion, an indicator of protein fermentation, was significantly decreased after 2 weeks of AXOS intake. The levels of bifidobacteria were significantly increased after 2 and 3 weeks of AXOS intake as well as after 3 weeks of placebo. However, the effect of AXOS on bifidobacteria was more pronounced than that of placebo. In conclusion, AXOS are a well-tolerated prebiotic at the dose of 10 g/d. AXOS intake increases faecal bifidobacteria and reduces urinary p-cresol excretion.

Aberrant social and cerebral responding in a competitive reaction time paradigm in criminal psychopaths

In a previous study (Lotze et al., 2007) we described dorsal medial prefrontal cortex (mPFC) activation in healthy subjects during retaliation in a competitive reaction time task. Interestingly, the less callous the subjects were, the more they responded with ventral mPFC-activation when watching the opponent suffering. In this study we used this paradigm to investigate behavioral and neural responding of ten criminal psychopathic individuals from a forensic psychiatric institution. In contrast to healthy subjects, who show reactive aggressive behavior of inflicting punishment with increasing intensity after experiencing an increasing amount of punishment from a yoked opponent, psychopathic participants did not react with comparable retaliation. However, when psychopaths punished with a high amount they showed increased activation in the hypothalamus, the lateral prefrontal cortex, the posterior cingulate cortex and the amygdala. The trait “physical aggression” showed a positive correlation with hypothalamic activation. Medial prefrontal areas, associated with emotional control and conflict management in healthy subjects performing this paradigm, were inactive in psychopathic subjects during retaliation. When psychopaths observed the yoked opponent being punished they showed increased activation in the dorsal and ventral medial prefrontal cortex, which was positively associated by impulsivity and antisocial behavior of Hare's psychopathy construct. This finding supports the notion that reactive aggression is more related to antisocial behavior and anger management than with emotional and interpersonal characteristics of psychopathy and suggests that two separate brain activation patterns seem to account for these two behavioral dispositions.

Effect of dark chocolate on plasma epicatechin levels, DNA resistance to oxidative stress and total antioxidant activity in healthy subjects

Dark chocolate (DC) may be cardioprotective by antioxidant properties of flavonoids. We investigated the effect of DC (860 mg polyphenols, of which 58 mg epicatechin) compared with white chocolate (WC; 5 mg polyphenols, undetectable epicatechin) on plasma epicatechin levels, mononuclear blood cells (MNBC) DNA damage and plasma total antioxidant activity (TAA). Twenty healthy subjects followed a balanced diet (55 % of energy from carbohydrates, 30 % from fat and 1 g protein/kg body weight) for 4 weeks. Since the 14th day until the 27th day, they introduced daily 45 g of either WC (n 10) or DC (n 10). Whole experimental period was standardised in antioxidant intake. Blood samples were collected at T(0), after 2 weeks (T(14)), 2 h and 22 h after the first chocolate intake (T(14+2 h) and T(14+22 h)), and at 27th day, before chocolate intake (T(27)), 2 h and 22 h after (T(27+2 h) and T(27+22 h)). Samples, except for T(14+2 h) and T(27+2 h), were fasting collected. Detectable epicatechin levels were observed exclusively 2 h after DC intake (T(14+2 h) = 0.362 (se 0.052) micromol/l and T(27+2 h) = 0.369 (se 0.041) micromol/l); at the same times corresponded lower MNBC DNA damages (T(14+2 h) = - 19.4 (se 3.4) % v. T(14), P < 0.05; T(27+2 h) = - 24 (se 7.4) % v. T(27), P < 0.05; T(14+2 h) v. T(27+2 h), P = 0.7). Both effects were no longer evident after 22 h. No effect was observed on TAA. WC did not affect any variable. DC may transiently improve DNA resistance to oxidative stress, probably for flavonoid kinetics.

Functional Structure of Spontaneous Sleep Slow Oscillation Activity in Humans

BackgroundDuring non-rapid eye movement (NREM) sleep synchronous neural oscillations between neural silence (down state) and neural activity (up state) occur. Sleep Slow Oscillations (SSOs) events are their EEG correlates. Each event has an origin site and propagates sweeping the scalp. While recent findings suggest a SSO key role in memory consolidation processes, the structure and the propagation of individual SSO events, as well as their modulation by sleep stages and cortical areas have not been well characterized so far.Methodology/Principal FindingsWe detected SSO events in EEG recordings and we defined and measured a set of features corresponding to both wave shapes and event propagations. We found that a typical SSO shape has a transition to down state, which is steeper than the following transition from down to up state. We show that during SWS SSOs are larger and more locally synchronized, but less likely to propagate across the cortex, compared to NREM stage 2. Also, the detection number of SSOs as well as their amplitudes and slopes, are greatest in the frontal regions. Although derived from a small sample, this characterization provides a preliminary reference about SSO activity in healthy subjects for 32-channel sleep recordings.Conclusions/SignificanceThis work gives a quantitative picture of spontaneous SSO activity during NREM sleep: we unveil how SSO features are modulated by sleep stage, site of origin and detection location of the waves. Our measures on SSOs shape indicate that, as in animal models, onsets of silent states are more synchronized than those of neural firing. The differences between sleep stages could be related to the reduction of arousal system activity and to the breakdown of functional connectivity. The frontal SSO prevalence could be related to a greater homeostatic need of the heteromodal association cortices.

Inspiratory resistive loading does not increase sympathetic tone in COPD

Neurohumoral activation has been shown to be present in patients with chronic obstructive pulmonary disease (COPD). The increase in respiratory muscle work might be responsible for the observed elevation of sympathetic tone via a respiratory muscle ergoreflex in these patients. The aim of this study is to investigate whether moderately increasing inspiratory resistive loading will impact on sympathetic activity in healthy subjects and COPD patients. Efferent muscle sympathetic nerve activity, blood pressure, heart rate and respiratory movements were continuously measured in 15 patients and 15 healthy control subjects. In order to increase work of breathing as evaluated by the tension-time index, inspiratory resistive loading was performed while patients were breathing through a spirometer. At baseline, sympathetic nerve activity was significantly elevated in patients. Resistive loading increased work of breathing (tension-time index) by roughly 110% (COPD) and 130% (controls) but did not significantly alter blood gases or sympathetic activity in either group. Doubling the work of breathing does not affect sympathetic activation in COPD patients or healthy control subjects. Thus in COPD the respiratory muscle ergoreflex does not seem to play a major role in sympathoexcitation.

Clenching and Grinding: Effect on Masseter and Sternocleidomastoid Electromyographic Activity in Healthy Subjects

This study compares the effect of clenching and grinding on masseter and sternocleidomastoid electromyographic (EMG) activity during different jaw posture tasks in the sagittal plane. The study included 34 healthy subjects with natural dentition, Class I bilateral molar Angle relationship, and absence of posterior occlusal contacts during mandibular protrusion. An inclusion criterion was that subjects had to be free of signs and symptoms of any dysfunction of the masticatory system. Bipolar surface electrodes were located on the right masseter and sternocleidomastoid muscles. EMG activity was recorded while the subjects were in standing position, during the following jaw posture tasks: A. maximal clenching in the intercuspal position; B. grinding from intercuspal position to edge-to-edge protrusive contact position; C. maximal clenching in the edge-to-edge protrusive contact position; D. grinding from edge-to-edge protrusive contact position to intercuspal position; E. grinding from retrusive contact position to intercuspal position. EMG activities in tasks B, C, D, and E were significantly lower than in task A in both muscles (mixed model with unstructured covariance matrix). EMG activity among tasks B, C, D, and E did not show significant differences in both muscles, except between tasks D and E in the masseter muscle. A higher effect was observed on the masseter than on the sternocleidomastoid muscle to avoid excessive muscular activity during clenching and grinding. The EMG patterns observed could be of clinical importance in the presence of parafunctional habits, i.e., clenching and/or grinding.

Ankle and Subtalar Kinematics during Dorsiflexion-Plantarflexion Activities

Understanding the effect of weightbearing on subtalar and ankle joint kinematics is critical for the diagnosis and treatment of foot disorders. However, dynamic in vivo kinematics of these joints are not well studied. The purpose of this study was to compare in vivo kinematics during nonweightbearing and weightbearing activities in healthy subjects. Seven healthy subjects with a mean age of 32 (range, 23 to 42) years were enrolled. Oblique lateral fluoroscopic images of nonweightbearing and weightbearing dorsiflexion-plantarflexion activities were recorded. Three dimensional subtalar, ankle, and ankle-subtalar joint complex kinematics were determined using 3D-2D model registration techniques with 3D bone models and single-plane fluoroscopy. During the weightbearing activity from 20 degrees dorsiflexion to 15 degrees plantarflexion, the subtalar joint was significantly more everted, dorsiflexed, and abducted, and the calcaneus showed a significantly more posterior position, than during the nonweightbearing activity. The ankle joint was significantly more plantarflexed and adducted during the weightbearing activity than the nonweightbearing activity. The ankle-subtalar joint complex was significantly more everted, and the calcaneus showed significantly greater posterior position than the nonweightbearing activity. These observations provide basic quantitative descriptions of weightbearing and nonweightbearing kinematics for healthy joints. These data can serve as the basis for comparison with pathologic feet for both diagnostic and therapeutic purposes.

Differential effects of acute cocaine and placebo administration on visual cortical activation in healthy subjects measured using BOLD fMRI

Many blood oxygenation level dependent (BOLD) functional magnetic resonance imaging studies have shown a strong response due to cocaine in brain regions with high concentrations of dopamine receptors. However, cocaine also has non-specific effects, including cardiovascular changes that may cause changes in BOLD signals, raising the possibility that measured changes could be due to these non-specific effects. The following experiment was conducted to address this concern. Subjects were given either cocaine or saline infusions during a long BOLD functional magnetic resonance imaging study. A flashing uniform-field stimulus, periodically alternating between on and off, provided a strong activation of primary visual cortex. There was a significant main effect of drug between cocaine and placebo. Although we did not demonstrate a significant drug × time interaction, BOLD signal changes associated with visual stimulation appeared unchanged after cocaine administration, whereas the signal differences appeared to decrease during placebo. Explanation of the differential response between the two groups may reflect cocaine expectancy instead of a direct effect of cocaine on BOLD signal changes but will require further investigation to fully elucidate.

Efavirenz Induces CYP2B6-Mediated Hydroxylation of Bupropion in Healthy Subjects

To characterize the effect of efavirenz on bupropion hydroxylation as a marker of cytochrome P450 (CYP) 2B6 activity in healthy subjects. Thirteen subjects received a single oral dose of bupropion SR 150 mg before and after 2 weeks of efavirenz administration for comparison of bupropion and hydroxybupropion pharmacokinetics. Efavirenz plasma concentrations were also assessed. Subjects were genotyped for CYP2B6 (G516T, C1459T, and A785G), CYP3A4 (A-392G), CYP3A5 (A6986G), and multidrug resistance protein 1 (C3435T). The area under the concentration vs. time curve ratio of hydroxybupropion:bupropion increased 2.3-fold after efavirenz administration (P=0.0001). Bupropion area under the concentration vs. time curve and Cmax decreased by 55% and 34%, respectively (P<0.002). None of the CYP2B6 or CYP3A genotypes evaluated were associated with a difference in bupropion or efavirenz clearance. The 2 individuals homozygous for multidrug resistance protein 1 3435-T/T had 2.5- and 1.8-fold greater bupropion and efavirenz clearance, respectively, relative to C/C and C/T individuals (P<0.05). Our results confirm that efavirenz induces CYP2B6 enzyme activity in vivo, as demonstrated by an increase in bupropion hydroxylation after 2 weeks of efavirenz administration.

Movement related activity in the high gamma range of the human EEG

Electrocorticographic (ECoG) recordings obtained using intracranially implanted electrodes in epilepsy patients indicate that high gamma band (HGB) activity of sensorimotor cortex is focally increased during voluntary movement. These movement related HGB modulations may play an important role in sensorimotor cortex function. It is however currently not clear to what extent this type of neural activity can be detected using non-invasive electroencephalography (EEG) and how similar HGB responses in healthy human subjects are to those observed in epilepsy patients. Using the same arm reaching task, we have investigated spectral power changes both in intracranial ECoG recordings in epilepsy patients and in non-invasive EEG recordings optimized for detecting HGB activity in healthy subjects. Our results show a common HGB response pattern both in ECoG and EEG recorded above the sensorimotor cortex contralateral to the side of arm movement. In both cases, HGB activity increased around movement onset in the 60–90 Hz range and became most pronounced at reaching movement end. Additionally, we found EEG HGB activity above the frontal midline possibly generated by the anterior supplementary motor area (SMA), a region that was however not covered by the intracranial electrodes used in the present study. In summary, our findings show that HGB activity from human sensorimotor cortex can be non-invasively detected in healthy subjects using EEG, opening a new perspective for investigating the role of high gamma range neuronal activity both in function and dysfunction of the human cortical sensorimotor network.

Effects of intranasal TNFα on granulocyte recruitment and activity in healthy subjects and patients with allergic rhinitis

BackgroundTNFα may contribute to the pathophysiology of airway inflammation. For example, we have recently shown that nasal administration of TNFα produces late phase co-appearance of granulocyte and plasma exudation markers on the mucosal surface. The objective of the present study was to examine indices of granulocyte presence and activity in response to intranasal TNFα challenge.MethodsHealthy subjects and patients with allergic rhinitis (examined out of season) were subjected to nasal challenge with TNFα (10 μg) in a sham-controlled and crossover design. Nasal lavages were carried out prior to and 24 hours post challenge. Nasal biopsies were obtained post challenge. Nasal lavage fluid levels of myeloperoxidase (MPO) and eosinophil cationic protein (ECP) were analyzed as indices of neutrophil and eosinophil activity. Moreover, IL-8 and α2-macroglobulin were analyzed as markers of pro-inflammatory cytokine production and plasma exudation. Nasal biopsy numbers of neutrophils and eosinophils were monitored.ResultsNasal lavage fluid levels of MPO recorded 24 hours post TNFα challenge were increased in healthy subjects (p = 0.0081) and in patients with allergic rhinitis (p = 0.0081) (c.f. sham challenge). Similarly, α2-macroglobulin was increased in healthy subjects (p = 0.014) and in patients with allergic rhinitis (p = 0.0034). Lavage fluid levels of ECP and IL-8 were not affected by TNFα challenge. TNFα increased the numbers of subepithelial neutrophils (p = 0.0021), but not the numbers of eosinophils.ConclusionTNFα produces a nasal inflammatory response in humans that is characterised by late phase (i.e., 24 hours post challenge) neutrophil activity and plasma exudation.

In vivo talocrural and subtalar kinematics during nonweightbearing and weightbearing dorsiflexion‐plantarflexion activities

Understanding of the effect of weightbearing on the kinematics of the subtalar and talocrural joints is critical for the diagnosis and treatment of foot and ankle disorders. However, precise kinematics of these joints during dynamic activities in vivo is not well studied. The purpose of this study was to compare in vivo kinematics of these joints during nonweightbearing and weightbearing activities in healthy subjects.

Effects of experimental muscle pain on shoulder-abduction force steadiness and muscle activity in healthy subjects

We previously demonstrated that the steadiness of shoulder abduction is reduced in patients with subacromial impingement syndrome (SIS), which might be related to shoulder pain associated with the SIS. The aim of the present study was to examine the acute effects of experimental shoulder muscle pain on shoulder motor function in healthy subjects. The fluctuations in exerted force (force steadiness) and electromyographic (EMG) activity from eight shoulder muscles were determined during sub-maximal isometric and dynamic contractions with the shoulder abductors in nine healthy subjects (27.7 +/- 4.2 years, mean +/- 1 SD) before, during and after experimental pain induction. Experimental pain was induced by bolus injections of 6% hypertonic saline into the supraspinatus muscle. Experimental muscle pain reduced shoulder-abduction force steadiness on average by 21% during isometric contractions (P = 0.012) and tended to do so during concentric contractions (P = 0.083). Middle deltoid, and infraspinatus and lower trapezius muscle activity increased (3-5% EMG(max)) during isometric and concentric contractions, respectively (P < 0.05). Thus, experimental shoulder muscle pain reduced the steadiness of isometric shoulder abduction and caused small changes in the abduction activation strategy. The observed effects of experimental pain on shoulder motor function differed from that observed previously in patients with SIS and chronic pain during the same types of contractions. A possible explanation may be that, even though the adopted experimental pain-paradigm may reflect the SIS in terms of the painful structures, it might not reflect the adaptations in the central nervous system seen with chronic pain.

Artemisinin and CYP2A6 activity in healthy subjects

To investigate whether the antimalarial drug artemisinin affects CYP2A6 activity in healthy subjects and to compare the utility of coumarin and nicotine as in vivo probe compounds for CYP2A6. Twelve healthy male Vietnamese subjects were given coumarin or nicotine in randomized sequence before and after 5 days of a repeated oral administration of artemisinin during two different treatment periods 1 month apart. Sequential blood samples were drawn at baseline 7 days prior to artemisinin treatment and on the first and fifth day of artemisinin treatment during both treatment periods. Plasma concentrations of 7-hydroxycoumarin glucuronide (7-OHCG), nicotine, cotinine and artemisinin were analysed by high-performance liquid chromatography and those of coumarin and 7-hydroxycoumarin (7-OHC) were determined by liquid chromatography-tandem mass spectrometry. Urine, collected in two time intervals on the days of coumarin intake, was treated with beta-glucuronidase and analysed for 7-OHC levels. Artemisinin AUC(0-infinity) values decreased significantly to 23% [95% confidence interval (CI) 18%-28%] on the fifth day of artemisinin administration as compared with the first. The sum of renally excreted 7-OHC and 7-OHCG increased by 1.55-fold (adjusted 95% CI 1.08-2.23) in the 3- to 8-h interval compared to baseline 7 days before. The 7-OHCG/7-OHC plasma AUC(0-infinity) ratio increased by 1.72-fold (adjusted 95% CI 1.16-2.54) following 5 days of artemisinin intake. There was no significant change in the cotinine/nicotine AUC(0-11 hr) ratio between study days. Artemisinin significantly increased the sum of renally excreted 7-OHC and 7-OHCG in one of the two collection intervals, suggesting an induction of CYP2A6. A significant increase in the 7-OHCG to 7-OHC AUC(0-infinity) ratio indicates artemisinin to be an inducer of glucuronidation.

Evaluation of a method for measuring tissue non-specific alkaline phosphatase activity in healthy subjects

Intestinal alkaline phosphatase (IAP) isozymes in the healthy human serum samples appears in two isoforms: normal-molecular-weight IAP (NIAP) and high-molecular-weight IAP (HIAP). We have demonstrated that the reference range for serum alkaline phosphatase (ALP) activity is higher in blood group B and O antigen secretors than in the tested other blood groups, for the appearance of these isoforms is depended on blood group B or O antigen secretors. We assessed a diethanolamine-L-phenylalanine (DEA-Phe) method for measuring tissue non-specific alkaline phosphatase (TNAP). This assays the sum of liver alkaline phosphatase and bone alkaline phosphatase activities as determined by an inhibiting IAP activity method with Phe. We classified 420 healthy subjects into two groups, a group of subjects who had blood group B or O antigen secretors (n = 184) and a group of subjects who had other blood groups (n = 236). ALP activity was higher in the B or O secretor group than in the other group: 20.9% higher (P<0.001) by the N-methyl-D-glucamine method, 13.7% higher (P<0.002) by 2-amino-2-methyl-1-propanol method, and 9.6% higher (P<0.05) by the diethanolamine method, but there was no significant difference in TNAP activity between the two blood group when measured by the DEA-Phe method. These results of this study support the expectation that the DEA-Phe method would be specific for TNAP activity. In addition, the reference range for TNAP activity did not vary with the differences in the tested all blood groups.