A longitudinal environmental surveillance study for SARS-CoV-2 from the emergency department of a teaching hospital in Hong Kong.

BACKGROUND: Understanding factors associated with SARS-CoV-2 exposure risk in the hospital setting may help improve infection control measures for prevention. AIM: To monitor SARS-CoV-2 exposure risk among healthcare workers and to identify risk factors associated with SARS-CoV-2 detection. METHODS: Surface and air samples were collected longitudinally over 14 months spanning 2020-2022 at the Emergency Department (ED) of a teaching hospital in Hong Kong. SARS-CoV-2 viral RNA was detected by real-time reverse-transcription polymerase chain reaction. Ecological factors associated with SARS-CoV-2 detection were analysed by logistic regression. A sero-epidemiological study was conducted in January-April 2021 to monitor SARS-CoV-2 seroprevalence. A questionnaire was used to collect information on job nature and use of personal protective equipment (PPE) of the participants. FINDINGS: SARS-CoV-2 RNA was detected at low frequencies from surfaces (0.7%, N = 2562) and air samples (1.6%, N = 128). Crowding was identified as the main risk factor, as weekly ED attendance (OR = 1.002, P=0.04) and sampling after peak-hours of ED attendance (OR = 5.216, P=0.03) were associated with the detection of SARS-CoV-2 viral RNA from surfaces. The low exposure risk was corroborated by the zero seropositive rate among 281 participants by April 2021. CONCLUSION: Crowding may introduce SARS-CoV-2 into the ED through increased attendances. Multiple factors may have contributed to the low contamination of SARS-CoV-2 in the ED, including hospital infection control measures for screening ED attendees, high PPE compliance among healthcare workers, and various public health and social measures implemented to reduce community transmission in Hong Kong where a dynamic zero COVID-19 policy was adopted.

Lower WNT16 expression in patients with adolescent idiopathic scoliosis - potential link to lower bone mass in AIS?

Adolescent Idiopathic Scoliosis (AIS) occurs during pubertal rapid growth period and is closely associated with low bone mass. The underlying mechanisms for systemic low bone mass in AIS remains unclear. Wnt signalling pathway is one of the important pathways regulating bone metabolism and influencing bone strength, its family member Wnt16 associates with lower bone mineral density (BMD) in late adulthood, and plays key regulatory role in determining cortical bone quality in adult mice. Our randomized control trial have reported vitamin D (VitD) supplementation significantly improved bone mass and reduced the risk of curve progression in AIS. A case-control study and animal study were employed to answer if WNT16 is associated with the abnormal bone quality in AIS and if the effect of VitD supplementation is associated with Wnt16, respectively. A cohort of 161 AIS and control female subjects were recruited for measurement of anthropometric parameters, bone qualities, and circulating Wnt16 level. In animal study, WT and Wnt16 gKO mice were both subjected to special VitD diet from week 4 and terminated at week 7 and 10 for samples harvesting. AIS showed significantly lower BMD, circulating WNT16 level, and elevated serum level of type I procollagen N-terminal propeptide. Wnt16 gKO mice demonstrated lower cortical bone density compared with WT mice from week 7 of age and Wnt16 gKO were less prone to cortical bone loss induced by high dosage VitD diet. Further study on the biological role of WNT16 and crosstalk with VitD metabolism on bone qualities is warranted which might shed light on prognostic gene of osteopenia and new perspectives for potential target to prevent curve progression.

Role of differentially expressed LBX1 in Adolescent Idiopathic Scoliosis (AIS) paraspinal muscle phenotypes and muscle-bone crosstalk through modulating myoblasts.

AIS is three-dimensional spinal deformity with unclear etiopathogenesis. LBX1 is so far the only multi-centers validated AIS predisposing gene. The imbalance of posterior paraspinal muscles is an important factor in AIS etiopathogenesis. It is poorly understood how LBX1 contributes to the abnormal paraspinal muscles and onset/progression of AIS. We aimed to evaluate the expression of LBX1 in paraspinal muscles at the concave and convex side in AIS, and whether alternation of LBX1 expression could affect myoblastsactivities and potentially influence muscle-bone interaction via myokines expression. Paraspinal muscles from AIS and age- and curvature-matched congenital scoliosis (CS) patients were collected for fiber types analysis. Biopsies were also subjected to qPCR to validate expression of myogenic markers, selected myokines and LBX1. Human skeletal muscle myoblast (HSMM) was used for LBX1 loss-of-function study in vitro. Muscle fiber types analysis showed type I and type IIX/IIAX fibers proportion were significantly different between AIS concave and convex but not in two sides of CS. LBX1, myogenic markers and one myokine were significantly imbalanced in AIS but not in CS. Loss-of-function study showed knockdown of LBX1 could inhibit myogenic markers expression and myokines as well. This study provides new insight into the association between imbalanced paraspinal muscle and potential muscle-bone crosstalk in AIS patients and the biological function of predisposing gene LBX1. Further investigation with appropriate animal models is warranted to explore if asymmetric expression of LBX1 could result in distinct muscle phenotypes and bone qualities thus affect the progression of spine curvature in AIS.

MiR-92b inhibits proliferation and invasion of lung cancer by targeting EZH2.

OBJECTIVE: To verify that miR-92b inhibits proliferation and invasion of lung cancer by targeting EZH2. MATERIALS AND METHODS: The expression levels of miR-92b and EZH2 in human bronchial epithelial cell line BEAS-2B and human lung cancer cell line (A549, NCI-H23, NCI-H358, NCI-H1975, PC-9) were detected, and miR-92b mimic, sh-EZH2 expression vector, and plasmid blank vector (blank group) were constructed. Blank group, miR-92b mimic, miR-92b mimic+sh-EZH2 group (combined group) were set up, MTT and transwell were used to detect the proliferation and invasion ability of A549 and NCI-H23 cells, and fluorescein report verified the regulatory relationship of miR-92b to EZH2. RESULTS: The expression level of miR-92b in A549, NCI-H23, NCI-H358, NCI-H1975, and PC-9 cells was lower than that in BEAS-2B cells (p<0.05). The expression level of EZH2 was higher than that of BEAS-2B cells (p<0.05). A549 and NCI-H23 cells were selected for transfection. After that, the expression level of miR-92 in miR-92b mimic, combined group A549 and NCI-H23 cells was higher than that in blank group (p<0.05), and miR-92b mimic had no difference with joint group (p>0.05). The expression level of EZH2 in cells of miR-92b mimic, blank group A549, and NCI-H23 was lower than that of combined group (p<0.05), and miR-92b mimic was lower than that of blank group (p<0.05). After the overexpression of miR-92b, pmirGLO-EZH2-3'UT Wt luciferase activity decreased significantly (p<0.05) but had no effect on pmirGLO-EZH2-3'UTR Mut Luciferase activity (p>0.05). Cell proliferation ability and invasion ability of A549 cells and NCI-H23 cells in miR-92b mimic group were lower than those in blank group (p<0.05), while those in combined group were higher than those in miR-92b mimic group (p<0.05). CONCLUSIONS: MiR-92b inhibits proliferation and invasion of lung cancer cells through targeted inhibition of EZH2, which is a potential target for future treatment of lung cancer.

Detection of Local Recurrence in Patients with Head and Neck Squamous Cell Carcinoma Using Voxel-Based Color Maps of Initial and Final Area under the Curve Values Derived from DCE-MRI.

BACKGROUND AND PURPOSE: Early detection of local recurrence is important to increase the chance of cure because local recurrence is the main cause of treatment failure in head and neck squamous cell carcinoma. We evaluated the added value of voxel-based color maps of dynamic contrast-enhanced MR imaging compared with conventional MR imaging alone for detecting local recurrence of head and neck squamous cell carcinoma. MATERIALS AND METHODS: We retrospectively enrolled 63 consecutive patients with head and neck squamous cell carcinoma after definitive treatment and posttreatment surveillance MR imaging studies that demonstrated focal enhancement at the primary site. Three independent readers assessed conventional MR imaging and a pair of color maps of initial and final 90-second time-signal intensity areas under the curve from dynamic contrast-enhanced MR imaging. The sensitivities, specificities, and accuracies of both conventional MR imaging alone and combined interpretation of conventional and dynamic contrast-enhanced MR imaging were assessed using the clinicopathologic diagnosis as the criterion standard. κ statistics were used to evaluate interreader agreement. RESULTS: There were 28 patients with subsequently documented local recurrence and 35 with posttreatment change. Adding dynamic contrast-enhanced MR imaging to conventional MR imaging significantly increased the diagnostic accuracies for detecting local recurrence (48%-54% versus 87%-91%; P < .05), with excellent interreader agreement (κ = 0.8; 95% CI, 0.67-0.92 to κ = 0.81; 95% CI, 0.69-0.93). By all 3 readers, the specificities were also significantly improved by adding dynamic contrast-enhanced MR imaging to conventional MR imaging (22%-43% versus 87%-91%; P < .001) without sacrificing the sensitivities (68%-82% versus 86%-89%; P > .05). CONCLUSIONS: Adding voxel-based color maps of initial and final 90-second time-signal intensity areas under the curve from dynamic contrast-enhanced MR imaging to conventional MR imaging increases the diagnostic accuracy to detect local recurrence in head and neck squamous cell carcinoma by improving the specificity without sacrificing the sensitivity.

Intratumoral Polymorphism of Peroxisome Proliferator-Activated Receptor Delta-87 T>C in Colorectal Cancer.

Peroxisome proliferator activated receptor delta (PPARD) is a nuclear receptor transcription factor whose single nucleotide polymorphism (SNP), especially PPARD-87 T>C (rs2016520), may play an important role in expression regulation of PPARD. But its expression patterns as well as contribution in colorectal cancer (CRC) are still controversial. In this study, whether the intratumoral heterogeneity of polymorphism of PPARD-87 T>C (rs2016520) existed and its influence in CRC were investigated. Tumor masses from primary CRC patients were collected during the operation of tumorectomy, specimens at the different sites of the same tumor mass were sampled and stored individually. The SNP of PPARD-87 T>C was detected by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP), and the expression of PPARD in vivo was observed by immunohistochemistry. The correlation of PPARD -87 T>C intratumoral polymorphism and the clinicopathological parameters of patients was analyzed statistically. Tumor samples were collected from 106 CRC patients (70 males and 36 females) with an average age of 61.04±13.67 years. A total number of 808 samples (7.60±1.60 per patient) were mainly harvested at peripheral superficial (n=376), central superficial (n=163), invasive front (n=112) and mesenteric cancer foci (n=42) of tumor tissues as well as cancerous adjacent mucosa (n=104). PCR-RFLP analysis showed that T/T (n=460, 56.9%) and T/C (n=334, 41.3%) were the main genotypes of -87 T>C among these samples. Furthermore, intratumoral genotype of -87 T>C was homogeneous in 90 patients and heterogeneous in other 16 patients. The intratumoral heterogeneity was related to patients' age (P=0.016), tumor location (P=0.011) and the grade of differentiation (P=0.022). For patients with intratumoral heterogeneity, immunochemistry showed the expressions of PPARD were not influenced by T/T or T/C genotypes. Intratumoral heterogeneity of PPARD-87 T>C wildly existed in CRC, and associated with patients' age, tumor location and differentiation. However, the immunochemistry assay revealed that there's no significant link between heterogeneity and expression of PPARD.

Cataract risk of neuro-interventional procedures: a nationwide population-based matched-cohort study.

AIM: To demonstrate the risk of cataract associated with radiation exposure from neuro-interventional procedures. MATERIALS AND METHODS: This was a nationwide population-based, matched-cohort study. The exposed group (group E) comprised patients diagnosed with an aneurysm, cerebrovascular system anomaly, or subarachnoid haemorrhage who underwent a neuro-interventional procedure, such as brain digital subtraction angiography or endovascular embolisation. The comparison group (group C) included subjects who were never exposed to radiation from neuro-interventional procedures and were propensity score-matched by the date of enrolment, age, sex, and associated comorbidities. Multiple Cox proportional hazard regression analysis was used to estimate the hazard ratio (HR) of cataract risk due to radiation exposure while adjusting for potential confounding factors. RESULTS: There were 838 patients and 3,352 matched subjects in groups E and C, respectively. The incidence of cataracts was significantly greater among subjects in group E (adjusted HR [aHR] = 1.88; 95% confidence interval [CI] = 1.08-3.26), especially those aged >40 years (aHR = 2.14; 95% CI = 1.16-3.94). The number of computed tomography examinations was positively correlated, but not statistically significant, with an increased risk of cataract occurrence. CONCLUSIONS: Neuro-interventional procedures might be significantly associated with an increased risk of cataract occurrence.

[Measurement of morphological parameters of internal acousticmeatus using thin-section CT].

Objective: This study aimed to measure the morphological parameters of the internal acoustic meatus(IAM) and its adjacent structures using temporal-bone thin-section CT(computed tomography). Methods: CT images were obtained from 50 Chinese adult patients (25 males and 25 females, 100 sides) which had no visible lesion in the petrous part of the temporal bone and inner ear, the morphological parameters of all inner ear parts were sectionally measured on the specified plane using SPSS 22.0 software for statistical analysis. Results: The integral morphological characteristics of the IAM were observed. These results revealed that anterior-posterior diameter of the internal acoustic poer(IAP)(CD) was (6.93±1.85)mm, the superior-inferior diameter of the IAP(EF) was (4.40±0.86)mm, the length of the IAM(AB) was (9.30±1.60)mm, the superior-inferior diameter of the IAM(the intersection of inner 1/3 section and middle 1/3 section) was (4.13±0.83)mm, the superior-inferior diameter of the IAM(the intersection of middle 1/3 section and outer 1/3 section) was (4.61±1.02)mm, the anterior-posterior diameter of the IAM(the intersection of inner 1/3 section and middle 1/3 section) was (6.62±1.92)mm, the anterior-posterior diameter of the IAM(the intersection of middle 1/3 section and outer 1/3 section) was (6.28±1.65)mm, the depth of transverse crest (superior wall) was (3.10±0.75)mm, the depth of transverse crest (interior wall)the was (1.46±0.59)mm, the distance from transverse crest vertex A to the superior wall of the IAM was (2.05±0.42)mm, the distance from transverse crest vertex A to the interior wall of the IAM was (2.93±0.41)mm, the thickness of the superior bone wall of the IAM (the intersection of inner 1/3 section and middle 1/3 section) was (4.45±1.34)mm, the thickness of the superior bone wall of the IAM (the intersection of middle 1/3 section and outer 1/3 section) was (4.32±1.12)mm, the thickness of the superior bone wall of the IAM (the intersection of outer 1/3 section and transverse crest vertex) was (4.37±1.28)mm, and the appearance ratio of the cells in the whole IAM superior wall was 32%.The whole IAM assumed the shape of short cylinder, inclining about 1 cm outward, with the upper-lower diameter and anterior-posterior diameter about 5 mm. Conclusion: It is necessary for carrying out preoperative the temporal-bone thin-section CT to obtain the morphological parameters of the IAM, determine its basic morphology, and provide references to avoid damaging the other important structures during IAM surgeries.

Interobserver reproducibility of cervical lymph node measurements at CT in patients with head and neck squamous cell carcinoma.

AIM: To determine the interobserver reproducibility of measuring cervical lymph nodes at computed tomography (CT) in patients with head and neck squamous cell carcinoma (HNSCC) and to investigate the influence of finding extracapsular spread (ECS) at CT on measurement reliability. MATERIALS AND METHODS: The institutional review board approved the study protocol, and informed consent was obtained. A total of 146 patients with 224 suspicious lymph nodes underwent CT before treatment. Two observers independently measured the diameters (minimal axial, maximum axial, and maximum longitudinal diameter) and assessed the ECS using CT. The greatest diameter was defined as the largest among the three measured diameters. Interobserver variability was determined by the within-subject coefficient of variation, and interobserver agreement was determined by the intraclass correlation coefficient (ICC). RESULTS: The within-subject coefficients of variation were 7.8%, 7.6%, and 11.4% for the minimal axial, maximum axial, and greatest diameters, respectively. The ICC values for interobserver agreement were excellent for all diameter measurements (i.e., ICC >0.9). Minimum and maximum axial diameter measurements were statistically more reliable than the greatest diameter measurement (p=0.008 and p=0.0001, respectively). The presence of ECS on CT does not significantly affect the reliability of lymph node diameter measurements (p>0.05). CONCLUSION: Lymph node diameter measurement on CT is a highly reproducible and robust method. Additionally, imaging features of ECS do not affect reliability. Therefore, the measurement of lymph node diameter can be confidently performed in daily clinical practice or clinical trials.

[HBsAg clearance rate in patients with HBeAg-positive chronic hepatitis B: a comparative effect analysis based on the real world].

OBJECTIVE: To investigate HBsAg clearance rate in previously untreated patients with HBeAg-positive chronic hepatitis B (CHB) treated with nucleos(t)ides and interferons and its influencing factors based on the clinical diagnosis and treatment dat. METHODS: A retrospective cohort study was conducted in 1 767 previously untreated HBeAg-positive CHB patients who visited Beijing You'an Hospital from February 14, 2008 to December 31, 2012. HBsAg clearance rates were calculated for patients with different characteristics, and the Cox regression model was used to investigate the influencing factors for HBsAg clearance. RESULTS: The overall annual HBsAg clearance rate was 0.46% in 1767 patients, and in the patients treated with adefovir, entecavir, telbivudine, and common interferon, the annual HBsAg clearance rate was 0.52%, 0.47%, 0.45%, and 1.18%, respectively. No patients in the lamivudine and pegylated interferon-α groups experienced HBsAg clearance, which might be due to the small sample size. The univariate analysis showed that HBsAg clearance rate was associated with the patient's age when he/she visited the hospital and baseline HBsAg titer level. After adjustment for other factors, the patients treated with common interferon had a significantly higher possibility of HBsAg clearance than those treated with entecavir (HR = 8.33, 95% CI: 1.19-58.50, P = 0.0329), but the possibility of HBsAg clearance showed no significant difference between patients treated with other nucleos(t)ides and entecavir. The patients aged≥50 years had a probability of HBsAg clearance 4.92 times that of those aged < 50 years (HR = 4.92, 95% CI: 1.38-17.50, P = 0.0139) and the patients with baseline HBsAg titer level < 3 log10 IU/ml had a probability of HBsAg clearance 22.77 times higher than that of those with baseline HBsAg titer level≥3 log10 IU/ml (HR = 23.77, 95% CI: 6.17-91.51, P < 0.0001). CONCLUSION: The previously untreated CHB patients achieve a low annual HBsAg clearance rate under current antiviral therapeutic regimens, especially nucleos(t)ides. Baseline HBsAg titer level is closely associated with HBsAg clearance.

Predicting the Prognosis of Oral Tongue Carcinoma Using a Simple Quantitative Measurement Based on Preoperative MR Imaging: Tumor Thickness versus Tumor Volume.

BACKGROUND AND PURPOSE: Several studies indicated that tumor thickness or tumor volume might be helpful predictors for the prognosis of oral tongue squamous cell carcinoma. Our aim was to compare the value of tumor thickness versus tumor volume measurement based on preoperative MR imaging in predicting the prognosis of oral tongue squamous cell carcinoma, especially focusing on lymph node metastases and local recurrence. MATERIALS AND METHODS: Clinical, pathologic, and imaging data of patients with 46 oral tongue squamous cell carcinomas were retrospectively studied. Logistic regression analysis was used to evaluate the prognostic value of tumor thickness and tumor volume based on MR imaging. Receiver operating characteristic analysis was applied for the optimal cutoff value for the identified risk variable for prognosis. RESULTS: A higher intraclass correlation coefficient was achieved for the measurement of tumor thickness compared with tumor volume (0.990 versus 0.972). Multivariate analysis showed that tumor thickness was a significant predictor of lymph node metastases (P = .024), while tumor volume was not a significant predictor of either lymph node metastases or local recurrence (P > .05). Receiver operating characteristic results indicated that setting a tumor thickness of 8.5 mm as a cutoff value could achieve the optimal diagnostic efficiency for predicting lymph node metastases (area under the curve, 0.753; sensitivity, 0.889; specificity, 0.536). CONCLUSIONS: Tumor thickness based on preoperative MR imaging was useful in predicting the prognosis of oral tongue squamous cell carcinoma, especially lymph node metastases, in our patient population, while tumor volume was not.

Chinese herbal medicine-induced anticholinergic poisoning in Hong Kong.

OBJECTIVE: To study the epidemiology, causes, and clinical course of Chinese herbal medicine-induced anticholinergic poisoning in Hong Kong. DESIGN: Case series. SETTING: Hong Kong. PATIENTS: All case histories of Chinese herbal medicine-induced anticholinergic poisoning (with laboratory confirmation) recorded by the Hong Kong Poison Information Centre over a 93-month period were accessed for analysis. RESULTS: During the relevant period, 22 clusters of Chinese herbal medicine-induced anticholinergic poisoning involving 32 patients were retrieved. The commonest clinical features were mydriasis (n=32, 100%) and confusion (n=24, 75%). No gastro-intestinal decontamination was performed. None of these patients underwent intubation, defibrillation, cardioversion, pacing, fluid resuscitation, inotropic support or dialysis. Of the 32 patients, 17 (53%) were treated with physostigmine because of confusion, three of whom had previously received intravenous benzodiazepines. No patient could be effectively treated with benzodiazepines alone. There was no mortality, and all the patients were discharged within 3 days. None of them re-attended the emergency department within 1 week of discharge. The commonest cause was the substitution of flos campsis (Campsis grandiflora) by the flower of the Datura species (7 clusters [32%] in 10 patients). CONCLUSION: Mydriasis and confusion were the commonest clinical features of Chinese herbal medicine-induced anticholinergic poisoning in Hong Kong. Physostigmine was frequently used in the treatment; benzodiazepines appeared ineffective. The commonest cause was the substitution of flos campsis (Campsis grandiflora) by the flower of the Datura species.

A huge malignant peripheral nerve sheath tumor with hepatic metastasis arising from retroperitoneal ganglioneuroma.

Ganglioneuromas (GNs) are the rarest and most benign of the neuroblastic tumors. We experienced a case of huge retroperitoneal GN which differentiated into malignant peripheral nerve sheath tumors (MPNST) with hepatic metastasis. The tumor was located in the upper right quarter of the abdomen and pressed the right lobe of the liver, which was initially misdiagnosed as a liver carcinoma. The tumor shared blood supply with the right liver lob and had rich blood supplies from the abdominal aorta, renal artery and hepatic artery. It was also associated with skin pigment and recurrence shortly following resection. Our finding demonstrated that MPNST is a potent invasive malignant tumor and metastasis earlier with very poor prognosis.

Uranium toxicity and speciation during chronic exposure to the tropical freshwater fish, Mogurnda mogurnda.

The effects of chronic uranium (U) exposure on larval Northern trout gudgeon, Mogurnda mogurnda, were assessed in two experiments using a newly-developed 28d survival and growth toxicity test. Significant effects were observed in both tests, but toxicity was markedly higher in Test 2 than Test 1. The LC50s for Tests 1 and 2 were 2090microgL(-1) and 1070microgL(-1), respectively. Larval growth IC10s for Tests 1 and 2 were 860microgL(-1) and 660microgL(-1) (dry weight), and 1160microgL(-1) and 850microgL(-1) (length), respectively. Uranium speciation modelling showed that a lower pH in Test 2 (mean of 6.0) compared to Test 1 (mean of 6.7) resulted in a greater proportion of free uranyl ion (UO(2)(2+)), the predominant bioavailable form of U. A higher dissolved organic carbon concentration (DOC) in Test 2 (4.2mgL(-1)) compared to Test 1 (2.1mgL(-1)) resulted in a higher proportion of U-DOC in Test 2, but this was insufficient to counter the effect of pH on the proportion of UO(2)(2+). The difference in U toxicity between the two tests could be explained by normalising for UO(2)(2+); the concentrations of UO(2)(2+) at the LC50s for Tests 1 and 2 were calculated to be 13.3 and 13.7microgL(-1), respectively. Finally, the results of this study, and comparisons with other studies suggest that U toxicity to M. mogurnda appears to be as much, if not more, a function of exposure water quality and feeding regime, as exposure duration.

Counterion Triple Layer in Solid/Solution Interface: Stirring and Temperature Effects on pH Measurements.

This paper reports on the pH glass electrode potential based on the double-capacitor theory and the discovery of a mobile counterion triple layer next to the double layer to explain the electrode potential changes caused by stirring and temperature increase. This mobile triple layer behaves like a rubberband, which may be loosened by stirring (or agitation) and temperature increase and tightened after stirring stops or temperature lowers. Stirring and temperature exert different effects on the potential of the pH and SCE electrodes via their different mechanisms. In contrast to the past, results reported here were obtained from experiments designed with the glass electrode and SCE in separate beakers connected with a conducting wire, so that one electrode could be stirred while keeping the other unstirred. There is a weak charge attraction between the double and triple layers, not a strong covalent bonding for complexation, so that the latter can be removed by stirring or temperature increase. In light of present results and the new concept, the Boltzmann equation has been modified to include the net charge density and the triple-layer potential. The counterion triple layer concept will have a tremendous impact on our understanding of the interface structure and properties, and stimulate further studies and applications of ion-selective electrodes. Copyright 2001 Academic Press.

Multivariate spectrofluorimetry of ultra trace zirconium(IV) and hafnium(IV) assisted by several chemometrics methods.

In the presence of sodium lauryl sulfate (SLS), an anionic surfactant, highly sensitive molecular fluorescence reactions occur between Zr(IV), Hf(IV) ions and quercetin (3, 3', 4', 5, 7-pentahydroxyflavone) in acidic medium to form stable ternary micellar ion-association complexes. Their lambda(ex(max))/lambda(em(max)) values are 435.0/497.9 and 435.0/492.0 nm, respectively, indicating their heavily overlapping fluorescence excitation and emission spectra. The linear ranges of their regression calibration curves are 0 to 0.20 and 0 to 0.12 mg l(-1), respectively, with 0.5 ng ml(-1) for all of sensitivities. The multivariate spectrofluorimetry of ultra trace or trace Zr(IV) and Hf(IV) without separation was performed using a partial least squares (PLS) algorithm and other algorithms. The optimum PLS computation conditions are wavelength point number of 21 and corresponding wavelength range from 450 to 540 nm oriented from lambda(em) 495 nm to two sides at combined intervals of 2.5 and 5.0 nm at a fixed lambda(ex)of 435.0 nm with an optimum calibration sample number of 12, and respective optimum abstracted factor numbers of 4 and 5. It was concluded that accuracy and precision of the determination results obtained for simulation and real soil samples were poor for LP-M, LP-P, OLS-P, KF-P, and TFA-P algorithms, moderate for OLS-M, KF-M, and TFA-M algorithms, and good for PLS algorithm.

Oral cimetidine prolongs clarithromycin absorption.

The present study was conducted to identify any potential interaction between oral cimetidine and clarithromycin. Twelve healthy subjects were administered single doses of clarithromycin alone and with oral cimetidine dosed to steady state. Cimetidine prolonged the absorption of clarithromycin, as evidenced by decreased peak concentrations of both clarithromycin and 14-OH-clarithromycin (14OHC) in serum (46 and 43%, respectively), a delay in the formation of 14OHC (increase of 68%), and increases in both of their half-lives (75 and 82%, respectively), despite no changes in total oral clearance or area under the concentration-time curve for either compound. No mechanism for this interaction has been identified.